Yaqi Cao, Tingting Liu, Zuobo Yang et al.

ChemElectroChem • 2024

Abstract The synthesis of efficient and stable Pt alloy catalysts is a major challenge for the commercialization of PEMFC. Herein, we report a PtCo/C(N) electrocatalyst prepared by Na 2 CO 3 ‐assisted urea liquid‐phase deposition strategy as an efficient cathodic oxygen reduction reaction electrocatalyst, and test its activity and stability in a rotating disc electrode and a single‐cell. The membrane electrode prepared with PtCo/C(N)‐800 °C catalyst has an output voltage of 0.652 V at 2 A/cm 2 and a maximum power density of 1.501 W/cm 2 , which are 36 mV and 81 W/cm 2 higher than those of commercial Pt/C catalyst, respectively. In addition, the mass activity and half‐wave potential of PtCo/C(N)‐800 °C are 2.44 times and 50 mV higher than those of commercial Pt/C, respectively. After 5000 voltammetric cycles, its mass activity and half‐wave potential only lose 35 A/g Pt and 9 mV, respectively. XPS results show that the binding energy of Pt 4f is positively shifted relative to Pt/C‐TKK, and the d‐band center of Pt decreases, leading to weak chemical interaction between the oxygen‐containing intermediate and the surface of the electrocatalyst, which is conducive to the improvement of the ORR activity and stability of the catalyst.

Yunseong Ji, Ohchan Kwon, Ok Sung Jeon et al.

Science Advances • 2023

To achieve a sustainable society, CO 2 emissions must be reduced and efficiency of energy systems must be enhanced. The polymer electrolyte membrane fuel cell (PEMFC) has zero CO 2 emissions and high effectiveness for various applications. A well-designed membrane electrolyte assembly (MEA) composed of electrode layers of effective materials and structure can alter the performance and durability of PEMFC. We demonstrate an efficient electrode deposition method through a well-designed carbon single web with a porous 3D web structure that can be commercially adopted. To achieve excellent electrochemical properties, active Pt nanoparticles are controlled by a nanoglue effect on a highly graphitized carbon surface. The developed MEA exhibits a notable maximum power density of 1082 mW/cm 2 at 80°C, H 2 /air, 50% RH, and 1.8 atm; low cathode loading of 0.1 mg Pt /cm 2 ; and catalytic performance decays of only 23.18 and 13.42% under commercial-based durability protocols, respectively, thereby achieving all desirables for commercial applications.

Saddam Husain Dhobi, Jeevan Jyoti Nakarmi, Suresh Prasad Gupta et al.

Journal of Nepal Physical Society • 2024

The objective of this work is to develop a theoretical model, to study the effect of quantum species, activation potential, current density, and temperature on the performance of Pt/C catalysts in Proton Exchange Membrane Fuel Cells (PEMFCs). For this we modified Butler-Volmer equations and analyzing I-V characteristics, the observation shows lower activation potential of 40 mV yields better performance compared to 55 mV. The effect of temperature was observed showing that increased in temperatures can mitigate carbon support corrosion and decline the performance of PEMFCs. Also increasing the electron flow per reaction cycle decrease the performance of PEMFCs by screening the flow of electron by quantum species formed around anode of PEMFCs. This result bring negative voltage and power, highlighting the complex interplay between these factors. The results underscore the importance of optimizing activation potential and managing temperature to enhance PEMFCs performance and longevity.

Andrew M. Baker, Joseph H Dumont, Rangachary Mukundan et al.

ECS Meeting Abstracts • 2017

Cerium enhances the durability of polymer electrolyte membrane (PEM) fuel cells by scavenging reactive radical species which are generated during operation. However, during cell fabrication, conditioning, and discharge, Ce migrates through-plane between the PEM and catalyst layers (CLs) due to concentration and potential gradients. 1,2 In addition, we have observed in-plane Ce migration due to water gradients and also identified degradation of Ce-exchanged PEM side chains as another possible mechanism for Ce migration. 3 Ce migration is detrimental because (1) its accumulation in the CL ionomer can diminish the electrode’s proton conductivity, which generates performance losses 4 ; and (2) its depletion may leave an ionomer region more susceptible to radical attack. Therefore, it is critical to understand the relative influence of different migration mechanisms under a range of operating conditions in order to stabilize Ce in the PEM and localize it to areas of highest radical generation. To understand the effects of potential gradients and relative humidity (RH) on Ce migration, ex situ experiments were performed using uncatalyzed Nafion® XL PEMs (DuPont) which contain ~6 μg/cm 2 ion-exchanged Ce. PEM specimens were operated in H 2 pump mode in a standard conductivity cell (BekkTech) at 80°C with 50% and 100% RH H 2 . The evolution of Ce profiles was quantified using X-ray fluorescence (XRF). By comparing the resulting profiles at 4 C of charge transfer for the different potential and RH conditions (Figure 1a), we observe decreased Ce transference at low RH. Under these conditions, decreased PEM water content causes a disproportionate reduction in Ce conductivity relative to proton conductivity. In these experiments, Ce ion mobility induced by a potential gradient leads to a concentration gradient, which, in turn, induces Ce diffusion in the opposite direction. Therefore, the profiles shown in Figure 1a arise from a combination of ion mobility and back-diffusion due to the resulting concentration gradient. In order to decouple these effects, a transient, 1-D model was developed based on Nernst-Einstein ion mobility and Fickian diffusion, in order to solve for the ion mobility and diffusion coefficients. Experimental and model results for the 2 V, 100% RH case are shown in Figure 1b. At 100% RH, both diffusion and ion mobility coefficients were determined to be an order of magnitude higher than at 50% RH. In addition to migration within the PEM, Ce is stabilized in the cathode CL, likely in the CL ionomer and/or carbon CL supports. 3 Ce accumulation in the cathode catalyst layer was measured to degrade MEA performance. Different mechanisms have been proposed for the performance loss, including increased proton resistance within the CL, and a reduction of oxygen reduction reaction kinetics. However, the effect of each mechanism on performance loss is difficult to quantify. The relative influence of Ce poisoning on the cathode CL performance will also be discussed. Quantifying the different Ce migration mechanisms has provided a better understanding of the effects of Ce migration in the PEM and CL and the associated losses in operating performance. These results demonstrate that stable Ce compounds, which can be localized to areas of highest reactive radical generation, need to be developed to enhance PEFC durability without compromising performance. Acknowledgements This research is supported by the U.S. DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells Program manager: Dimitrios Papageorgopoulos. Prof. Ajay Prasad and Prof. Suresh Advani also acknowledge support from the University of Delaware’s Fuel Cell Bus Program. This program is funded by the Federal Transit Administration at the Center for Fuel Cell Research at the University of Delaware. References Stewart, S. M.; Spernjak, D.; Borup, R.; Datye, A.; Garzon, F. ECS Electrochem. Lett. 3 , F19–F22 (2014). Baker, A. M.; Mukundan, R.; Spernjak, D.; Advani, S. G.; Prasad, A. K.; Borup, R. L. ECS Trans. 75 , 707–714 (2016) Baker, A. M.; Mukundan, R.; Spernjak, D.; Judge, E. J.; Advani, S. G.; Prasad, A. K.; Borup, R. L. J. Electrochem. Soc. 163 , F1023–F1031 (2016). Banham, D.; Ye, S. Y.; Cheng, T.; Knights, S.; Stewart, S. M.; Wilson, M.; Garzon, F. J. Electrochem. Soc. 161 , F1075–F1080 (2014). Figure 1

Kyoungdoug Min, Jack Brouwer, John Auckland et al.

ASME 2006 Fourth International Conference on Fuel Cell Science, Engineering and Technology, Parts A and B • 2005

A dynamic model of a stationary PEM fuel cell system has been developed in Matlab-Simulink®. The system model accounts for the fuel processing system, PEM stack with coolant, humidifier with anode tail-gas oxidizer (ATO), and an enthalpy wheel for cathode air. For the fuel processing system four reactors were modeled: (1) an auto thermal reactor (ATR) (2) a high temperature shift (HTS) reactor, (3) a low temperature shift (LTS) reactor, and (4) a preferential oxidation (PROX) reactor. Chemical kinetics for ATR that describe steam reformation of methane and partial oxidation of methane were simultaneously solved to accurately predict the reaction dynamics. Chemical equilibrium of CO with H2O was assumed at HTS and LTS reactor exits to calculate CO conversion corresponding to the temperature of each reactor. A quasi-two dimensional unit PEM cell was modeled with five control volumes for solving the dynamic species and mass conservation equations and seven control volumes to solve the dynamic energy balance and to capture the details of MEA behavior, such as water transport, which is critical to accurately determine polarization losses. The dynamic conservation equations, primary heat transfer equations and equations of state are solved in each bulk component and each component is linked together to represent the complete system. A comparison of steady-state model results to experimental data shows that the system model well predicts the actual system power and catalytic partial oxidation (CPO) temperature. Transient simulation of DC power is also well matched with the experimental results to within a few percent. The model predictions well characterized the observed dynamic CPO temperature, voltage, and temperature of stack coolant outlet observations that are representative of a generic PEM stationary fuel cell system performance. The model is shown to be a useful tool for investigating the effects of inlet conditions and for the development of control strategies for enhancing system performance.

R. Kunkel, N. Baumann, T. Jurzinsky et al.

Fuel Cells • 2019

Abstract An increasing use of fuel cell electric vehicles involves the need to understand their behavior at low ambient temperatures as well as under cold‐start conditions. Here commercial 60 wt.% Pt/C catalyst (HiSPEC9100) was studied in the temperature range 0–20 °C using rotating disc electrode (RDE) setup and single cell inside a climate chamber. RDE measurements of oxygen reduction reaction (ORR) activity revealed decreasing activity with lower temperatures as well as activation energies and reaction mechanisms comparable to high temperature studies. Catalyst degradation was significantly lower at lower temperatures, which was confirmed by CO stripping. The increase of the specific ORR activity after degradation measurements is discussed in terms of morphological changes of the Pt particles. Single cell tests confirmed significant performance reduction at lower temperatures. Furthermore, measurements at different power densities were conducted to evaluate heating and flooding effects.

Arwa Fraiwan, Douglas F. Call, Seokheun Choi

Journal of Renewable and Sustainable Energy • 2014

Application of micro-scale microbial fuel cells (MFCs) to power electronics is limited due to the high internal resistances associated with membranes. Laminar flow MFCs (LFMFCs) provide an advantage over conventional designs because the anode and the cathode are naturally separated due to the laminar flow regime that develops within the reactor, eliminating the need for membranes. However, our ability to fully harness the potential of LFMFC technology lags from a lack of in-depth understanding of anode/cathode analyte mixing and fundamental factors that maximize LFMFC's power-generating capabilities. We, therefore, investigated the anode colonization and respiration of the known exoelectrogenic bacterium, Geobacter sulfurreducens, in a micro-scale LFMFC. Current production was dependent on the location of the anode relative to the influent in continuous-flow operation, with the highest current density of 6.5 μA/cm2 recorded closest to the influent. Lateral diffusion of anode/cathode analytes, in addition to upstream substrate consumption, likely resulted in the observed differences in current production. As current increased, the number of bacterial cells on the anode measured using simultaneous microscopic observation, also increased. Although the current density obtained here was substantially lower than other micro-sized MFCs, these findings show that micro-scale LFMFCs adapted to microscopic observation can provide a unique tool for better understanding real-time anode colonization and overall reactor performance.

Giulia Massaglia, Tommaso Serra, Candido Fabrizio Pirri et al.

Preprints.org • 2023

The aim of this work is the development of new nanostructured-gas-diffusion-layer (GDL) to improve the overall behaviour of Air-Cathode Single-Chamber-Microbial-Fuel-Cells (SCMFCs). The design of new nanostructured-GDL allowed exploiting all nanofibers ’intrinsic properties, such as high surface ratio to volume, high porosity, achieving a good oxygen diffusion into the proximity of catalyst layer, favouring thus the direct oxygen-reduction-reaction (ORR). Nanostructured-GDLs were prepared by electrospinning process, using layer-by-layer deposition to collect 2 nanofibers’ mats. The first layer was made of cellulose nanofibers able to promote oxygen diffusion into SCMFC. The second layer, placed outwards, was based on polyvinyl-fluoride (PVDF) nanofibers to prevent the electrolyte leakage. This nanostructured-GDL plays a pivotal role to improve the overall performance of Air-Cathode-SCMFCs. A maximum current density of (132.2 ± 10.8) mA m-2 was obtained, which is two times higher than the one reached with commercial-PTFE (58.5 ± 2.4 mA m-2), used as reference material. All results were analyzed in terms of energy recovery parameter, defined as ratio of generated power integral and the internal volume of devices, evaluating the overall SCMFC performance. SCMFCs with a nanostructured-GDL showed an energy recovery one order of magnitude higher than the one obtained with commercial-PTFE.

Yuto Shirase, Junji Inukai, Koji Ohara et al.

ECS Meeting Abstracts • 2024

Introduction Anion-exchange membrane fuel cell (AEMFC) has a potential use of non-precious metal catalysts under an alkaline environment. Furthermore, anion-exchange membranes (AEMs) are also expected to be used for water electrolysis. One of the disadvantages of AEMFC is a lower performance at low relative humidity (RH). One of the reasons for this decrease in performance at low RH is the decrease in conductivity of the AEM and the increase in polarization of each electrode, mainly due to the decrease in back-diffusion of water. In order to solve this problem, it is necessary to elucidate the water behavior inside the AEM. Experiment As an AEM, QPAF-4 developed in the University of Yamanashi was used. Water uptake and swelling measurements were combined to investigate the quantitative behavior of water. Neutron reflectometry was conducted to analyze the water content associated with the humidification inside QPAF-4. Synchrotron radiation X-ray scattering was used to analyze the chemical bonding between water molecules inside QPAF-4. Small angle X-ray scattering (SAXS) was carried out to analyze the change in membrane structure associated with humidification inside QPAF-4. Conductivity measurements in the gas phase were carried out at different RHs. Result & Discussion From the measurements of the water uptake (The counter ion of QPAF-4 is Cl - ) and swelling (The counter ion of QPAF-4 is OH - ), it was understood that the water swelling abruptly increased at the RH higher than approximately 70%, whereas the water uptake steadily increased with increasing the RH. Therefore, there expected was a change in water states in the QPAF-4 membrane at high RHs. Fig. 1 shows the neutron reflectometry (The counter ion of QPAF-4 is Cl - ). At low RHs, the topmost sublayer was relatively humidified. Only at 90% RH, all sublayers in the membrane were hydrated. This result suggests that at 90% RH, the state of water in the membrane was different from those at lower RHs. Fig. 2 shows the radial distribution function of the QPAF-4 at different RHs obtained by synchrotron radiation X-ray scattering (The counter ion of QPAF-4 is Cl - ). A peak around 2.8 Å changed, showing the change in the interactions between OH in water molecules. The intensity of this peak increased with increasing RH. The peak width also changed with increasing RH especially from 70% to 90%RH, showing that at 90% RH, bonds between water with different distances appeared. Fig. 3 shows the results of SAXS (The counter ion of QPAF-4 is Cl - ). The scattering intensity and d-value of hydrophobic domain increased as the RH increased, but the difference was pronounced at 90% RH. Therefore, the periodicity and the repeating distance of the hydrophobic domain abruptly changed at 90% RH. Fig. 4 shows the results of OH - conductivity of QPAF-4 (The counter ion of QPAF-4 is OH - ). At low relative humidity, the conductivity did not change. Around 90%RH, the conductivity significantly increased. Therefore, the behaviors of water and conductivity were closely related. The hydrophilic paths and the states of water effective for the OH - might effectively appear at a high RH of 90%. Figure 1

Atsuya Yamakawa, Keisuke Todaka, Satomitu Imai

ECS Meeting Abstracts • 2020

An enzyme-type biofuel cell (EBFC) is a device that converts chemical energy into electrical energy by a redox reaction, using an enzyme as a catalyst to generate electricity. EBFCs have the features that it can operate at normal temperature, normal pressure, and neutrality. In addition, fuel can be selected depending on the type of enzyme, and the structure is simple and the easy to miniaturize. Therefore, EBFCs are expected to be a power source for medical and mobile devices. EBFCs have problems of low output and low lifetime. Hoshi et al. proposed using GCFC (large specific surface area) for the electrode, to improve the output [1]. EBFCs generally use oxygen in the cathode reaction. Therefore, oxygen supply is important in EBFCs. Kuroishi et al. reported on the improvement of output in air exposure type EBFCs using gel fuel [2]. However, the gel did not function well after a few minutes owing to drying i.e., they have a short lifetime. In this study, a new structure to solve these problems was proposed. In this study, fructose was used as the fuel. Figure 1 shows the operating principle of EBFCs using enzymes of fructose dehydrogenase (FDH) and bilirubin oxidase (BOD). Figure 2 shows the hybrid structure of liquid fuel and gel fuel, which was proposed in this work. The electrode uses GCFC. The distance between the two electrodes and the thickness of the gel fuel is 3 mm. The specifications of the used enzyme, liquid fuel, and gel fuel are shown in Table 1. Figure 3 shows the cyclic voltammetry (CV) of the anode to determine the optimum concentration of the fuel (200 mM). Next, we compared the power density of a conventional gel fuel cell (original gel fuel cell) and a fuel cell with liquid fuel dropped on the cathode side of gel fuel cell (cathode wetting gel fuel cell). Figure 4 shows the power density of the original gel fuel cell and the cathode wetting gel fuel cell. The power density of the cathode wetting gel fuel cell is extremely reduced. This indicates that the gel fuel cell requires the cathode to be dry to provide sufficient oxygen. Therefore, the hybrid structure was adopted to make the gel dry on the side of cathode and to prevent the drying of the gel by contacting with the liquid fuel on the side of the anode. Figure 5 shows the power density of the three types of EBFC. The power density of the hybrid was 74.0 μW / cm 2 , which is almost equivalent to that of just using gel. Figure 6 shows the time history of the maximum power density. The gel fuel type halved power density after 45 minutes. However, the hybrid type achieved a power density of 61 μW/cm 2 , even after 120 minutes. This was the most important feature of this study. Figure 7 confirms that the high level of the maximum power density, even after 24 hours, was maintained to at least 62.3% (46.1 μW/cm 2 ) of the initial value. [1] K. Hoshi et al. Jpn. J. Appl. Phys, 55 02BE05,2016 [2] K. Kuroishi et al. IEICE Transactions on Electronics, pp151-154,2019 Figure 1

, Yaneeporn Patcharavorachot

• 2009

To present a performance analysis of a planar solid oxide fuel cell (SOFC) fed by methane with direct internal reforming under an intermediate temperature operation. The electrolyte material used in SOFC was focused on an oxygen ion-conducting (SOFC-O2-) and a proton-conducting electrolyte (SOFC-H+). A detailed electrochemical model that takes into account all voltage losses (i.e., ohmic, activation and concentration losses) used in this study was validated with experimental data reported in literature. The characteristic performance of SOFC was analyzed by considering the role of support structure and the effect of design parameters. The simulation results showed that an anode-supported design of both the SOFCs gives the best performance. Further, it was found that decreasing electrolyte thickness and increasing electrode pore size and porosity can improve the performance of SOFC-O2- and SOFC-H+. A decrease in cathode thickness has less effect on the performance of SOFC-O2- whereas a decrease in anode thickness is less sensitive to the performance of SOFC-H+. The performance of the anode supported SOFC-O2- and SOFC-H+ under the direct internal reforming operation of methane and isothermal condition was analyzed based on a one-dimensional steady-state fuel cell model coupled with a detailed electrochemical model taking into account all various voltage losses. It was found that increases in operating temperature, pressure and steam to carbon ratio can enhance the efficiency of both the SOFCs. Under the operating temperature of 1073 K and pressure of 1 atm, the performance of SOFC-H+ was considerably lower than SOFC-O2- because a low protonic conductivity of electrolyte leads to much higher ohmic loss in the SOFC-H+. In case of SOFC-H+, the effect of water content in oxidant was considered and found that the SOFC-H+ performance decreases with an increase in water content in oxidant. Further, high CO content at a fuel channel was observed and this may hinder the SOFC-H+ performance by reducing catalyst activity. To avoid the problems associated with low actual performance and the presence of high CO content at the fuel channel of SOFC-H+, a SOFC combined system consisting of SOFC-O2- and SOFC-H+ was proposed in this research. The performance of the SOFC system was primarily evaluated by using the SOFC model based on the conservation of mass and a detailed electrochemical model. The results showed that the performance of the SOFC-O2- -SOFC-H+ combined system provides a higher efficiency compared with the use of a single SOFC. Further, it was indicated that increasing the operating temperature, pressure, degree of pre-reforming as well as decreasing the inlet fuel velocity and cell voltage can improve the efficiency of the SOFC system.

Jiang-Hao Tian, Rémy Lacroix, Elie Desmond-Le Quéméner et al.

bioRxiv (Cold Spring Harbor Laboratory) • 2019

Abstract Recent development of microbial electrochemical technologies has allowed microbial electrosynthesis (MES) of organic molecules with microbial electrolysis cell treating waste organic matter. An electrolytic cell with a MES cathode (ME-ME cell) can produce soluble organic molecules with higher market price than biomethane, and thus satisfy both economic and environmental interest. However, the sustainability of bioanode activity could become a major concern. In this work, a 15-liter ME-ME reactor was designed with specific electrode configurations. An electrochemical model was established to assess the feasibility and possible performance of the design, considering the “aging” effect of the bioanode. The reactor was then built and operated for performance evaluation as well as bioanode regeneration assay. Biowaste from an industrial deconditioning platform was used as substrate for bioanode. The COD removal rate in the anodic chamber reached 0.83 g day -1 L -1 of anolyte and the anodic coulombic efficiency reached 98.6%. Acetate was produced with a rate of 0.53 g day -1 L -1 of catholyte, reaching a maximum concentration of 8.3 g L -1 . A potential difference was applied between the bioanode and biocathode independent of reference electrodes. The active biocathode was dominated by members of the Genus Pseudomonas , rarely reported so far for MES activity.

Oluwaseun Adelaja, Tajalli Keshavarz, Godfrey Kyazze

Earthline Journal of Chemical Sciences • 2021

In this study, tubular microbial fuel cells (MFCs) were inserted into phenanthrene-contaminated water-logged soil in order to evaluate their treatment efficiency and overall system performance within 60 days’ incubation period. At day 10, phenanthrene degradation rates were found to decrease with increasing distance from the anodes from 50-55 % at 2 cm to 38-40 % at 8 cm. Bromate (used as a catholyte) removal in both MFCs was about 80-95 % on average which is significantly higher than the open circuit controls (15-40 %) over the 60day period. Total chemical oxygen demand removal (72.8 %) in MFCs amended with surfactants was significantly higher than MFCs without surfactant (20 %). This suggests that surfactant addition may have enhanced bioavailability of not only phenanthrene, but other organic matter present in the soil. The outcomes of this work has demonstrated the simultaneous removal of phenanthrene (86%) and bromate (95%) coupled with concomitant bioelectricity generation (about 4.69 mWm-2) using MFC systems within a radius of influence (ROI) up to 8 cm. MFC technology may be used for in situ decontamination of soils due to its potential detoxification capacity and could be deployed directly as a prototype-MFC design in field applications.

Bahaa A. Hemdan, Gamila E. El-Taweel, Sunandan Naha et al.

Scientific Reports • 2023

Abstract Formation of electrogenic microbial biofilm on the electrode is critical for harvesting electrical power from wastewater in microbial biofuel cells (MFCs). Although the knowledge of bacterial community structures in the biofilm is vital for the rational design of MFC electrodes, an in-depth study on the subject is still awaiting. Herein, we attempt to address this issue by creating electrogenic biofilm on modified graphite anodes assembled in an air–cathode MFC. The modification was performed with reduced graphene oxide (rGO), polyaniline (PANI), and carbon nanotube (CNTs) separately. To accelerate the growth of the biofilm, soybean-potato composite (plant) powder was blended with these conductive materials during the fabrication of the anodes. The MFC fabricated with PANI-based anode delivered the current density of 324.2 mA cm −2 , followed by CNTs (248.75 mA cm −2 ), rGO (193 mA cm −2 ), and blank (without coating) (151 mA cm −2 ) graphite electrodes. Likewise, the PANI-based anode supported a robust biofilm growth containing maximum bacterial cell densities with diverse shapes and sizes of the cells and broad metabolic functionality. The alpha diversity of the biofilm developed over the anode coated with PANI was the loftiest operational taxonomic unit (2058 OUT) and Shannon index (7.56), as disclosed from the high-throughput 16S rRNA sequence analysis. Further, within these taxonomic units, exoelectrogenic phyla comprising Proteobacteria , Firmicutes , and Bacteroidetes were maximum with their corresponding level (%) 45.5, 36.2, and 9.8. The relative abundance of Gammaproteobacteria , Clostridia , and Bacilli at the class level, while Pseudomonas , Clostridium , Enterococcus , and Bifidobacterium at the genus level were comparatively higher in the PANI-based anode.

Damiano Di Penta, Karim Bencherif, Michel Sorine et al.

Journal of Fuel Cell Science and Technology • 2006

This paper proposes a reduced fuel cell stack model for control and fault diagnosis which was validated with experimental data. Firstly, the electro-chemical phenomena are modeled based on a mechanism of gas adsorption/desorption on catalysts at the anode and at the cathode of the stack, including activation, diffusion, and carbon monoxide poisoning. The electrical voltage of a stack cell is then modeled by the difference between the two electrode potentials. A simplified thermal model of the fuel cell stack is also developed in order to take into account heat generation from reactions, heat transfers, and evaporation/condensation of water. Finally, the efficiency ratio is computed as a model output. It is used to evaluate the efficiency changes of the entire system, providing an important indicator for fault detection.

Jayapriya Jayaprakash, Abinaya Parthasarathy, Ramamurthy Viraraghavan

Environmental Progress & Sustainable Energy • 2016

A laboratory‐scale H‐shaped Pseudomonas catalyzed microbial fuel cell (MFC) was investigated for its performance in decolourizing synthetic wastewater containing azo dyes. The azo‐dyes investigated in this study were methyl orange (MO), congo red, reactive blue 172 (RB), reactive yellow 145, and reactive red 2. Among the azo dyes in anode chamber MO resulted in the highest power density (4100 μW m −2 ) with graphite electrodes and a decolourization efficiency of 94%. The azo bonds were cleaved in all the dyes tested, and their metabolites in the anolytes were characterized by UV‐visible spectral and HPLC analyses. To reduce the internal resistance of MFC and maximize the power density, different metal salt doped graphite epoxy composites) were tested. In the case of azo dyes MO and RB, the power output increased substantially (almost 1.2 fold) when using Mn 2+ —GECE compared to graphite block. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1623–1628, 2016

Yan Wang, Ying Jiang, Dong Pu Guo et al.

Advanced Materials Research • 2010

One of the most promising applications of MFC is to use them treating organic wastes while accomplishing power generation. In this study, the effects of different electrode sizes on electricity generation performance and COD removal were investigated in dual chambered MFC. It was found that the maximum power density of S-MFC (the electrode anode size is 74.5 cm2) and L-MFC (the electrode anode size is 77.67 cm2), with the external resistor was 300Ω, were 0.23mW/cm2 and 0.41mW/cm2, respectively. In the period of 0~400 h operation, the S-MFC reached the maximum voltage 71.5 mV in 308 hours with the maximum current 186.2 μA, while the L-MFC reached the maximum voltage 97.9 mV in 184 hours with the current 271.3 μA. Moreover, the anode solution COD removal of S-MFC ranged from 1.66% to 6.87% using Ag+ solution as the cathode and the anode solution COD removal in the L-MFC varied from 7.21% to 14.86%.

Tatiana Zonfa, Theofilos Kamperidis, Marica Falzarano et al.

Fermentation • 2023

The present work investigates a two-stage process scheme for cheese whey valorization through energy recovery in different forms by means of bio-electrochemical systems. The first stage consisted of an integrated bio-electrochemical process for H2 and electricity production. This combined dark fermentation with an electrochemical system with the aim of overcoming the typical thermodynamic/biochemical limitations of fermentation and enhancing H2 recovery. The second treatment stage involved a single-chamber microbial fuel cell, featuring an innovative configuration consisting of four air cathodes with fly ash as the oxygen reduction catalyst. The bio-electrochemical process performed in the first stage achieved promising results, displaying a three-times higher H2 production yield compared to conventional dark fermentation. In addition, the experiments using the MFC in the second stage were found to successfully exploit the effluent from the first stage, with COD removal yields of 86% ± 8% and energy recovery with a maximum current output of 1.6 mA and a maximum power density of 1.2 W/m3.

Aliyu Ishaq, Mohd Ismid Mohd Said, Shamila Binti Azman et al.

Environmental Science and Pollution Research • 2024

Abstract Microbial fuel cells (MFCs), hailed as a promising technology, hold the potential to combat various wastewater pollutants while simultaneously converting their chemical energy into electricity through biocatalysts. This study explores the applicability of a dual compartment MFC (DC-MFC) under varying conditions, targeting the removal of chemical oxygen demand (COD) from landfill leachate and electricity generation. In this setup, anaerobic sludge from a wastewater treatment plant serves as the inoculum in the anode compartment of the MFC, with a Nafion117 membrane acting as the separator between MFC units. The cathode compartments are filled with distilled water and continually aerated for 24 h to enhance air supply. The study assesses the MFC’s performance across different COD concentrations, focusing on COD removal, power generation, and Coulombic efficiency. The findings reveal that COD removal efficiency is notably enhanced at higher concentrations of organic matter. Specifically, at a COD concentration of 3325.0 mg L −1 , the MFC exhibited the highest COD removal efficiency (89%) and maximum power density (339.41 mWm −2 ), accompanied by a Coulombic efficiency of 25.5%. However, as the initial substrate concentration increased to 3825 mg L −1 , the efficiency decreased to 72%, with a Coulombic efficiency of 13.56% and a power density of 262.34 mWm −2 . Optical density levels increased due to bacterial growth at ambient temperature and neutral pH, reflecting the dynamic microbial response within the system.

Santanu Dey, Subhamay Pramanik, Pradipta Chakraborty et al.

Research Square • 2022

Abstract Although direct glucose fuel cell (DGFC) is considered as a promising energy supply system, the poor catalytic activity and substandard stability of most catalysts during glucose electro-oxidation is a serious drawback for its possible applications. In this study, different bismuth nanostructures are proposed as efficient anode electrocatalysts for the oxidation of glucose in alkaline medium. Bismuth nanospheres with smaller diameter were prepared by hydrothermal method, giving rise to active surface area and electrocatalytic performance as well toward glucose electro-oxidation. Among the prepared Bi electrocatalysts of different morphologies, uniformly spherical three dimensional structure displayed improved current density as high as 79.78 mAcm − 2 during glucose oxidation in 1 M NaOH + 6 mM glucose solution tested at 100 mVs − 1 CV scan rate. The cycling stability of the prepared catalyst was examined for 100 cycles and it showed the 79.5% retention of activity after 100 cycles. In our investigation, bismuth nanospheres having smaller diameter showed best catalytic performance. The notable electrocatalytic performance of Bi nanostructures (mainly Bi nanosphere) may make possible to design and progress of renewable power device.

Natalia Macauley, Rod L. Borup, Rangachary Mukundan et al.

ECS Meeting Abstracts • 2016

The development of stratified catalyst layers promises an increase in catalyst layer performance compared to conventional flat catalyst layers. 1,2 Irregular catalyst layer thickness and porosity can lead to enhanced gas and water transport in and out of the catalyst layer, respectively. The stratified structure is expected to have the same performance in the kinetic region where the performance is controlled by the overall Pt loading. However at high current densities, the thinner sections of the stratified catalyst layers should allow for better mass transport properties. Electrode fabrication is done in house with a custom designed spray coating procedure and catalyst ink recipe. Various approaches are being explored to achieve the desired electrode structure. One approach is to densify the catalyst layer in localized regions, and is based on Ion Power proprietary manufacturing techniques. This can involve the use of glass epoxy masks during the spray coating process to directly create a patterned electrode on the membrane that has thicker and thinner regions. Figure 1 illustrates the effect of stratification on the fuel cell performance of a MEA. The second approach is to pattern thicker and thinner sections of an electrode using masks. During spray coating, one mask exposes the lands and the other mask exposes the channels. This way the two extreme cases can be investigated and the resulting performance compared. The concept of having more catalyst material in the channels may be beneficial due to rapid reaction times during influx of reactant gases through the channels. However, the presence of a thicker catalyst layer under the channel may later become an issue for product water removal and oxygen diffusion. On the other hand, spray coating more of the electrode in the land areas may support better product water removal and oxygen diffusion by leaving a thinner catalyst layer under the channels. The best performance is expected from a combination of ordered thin and thick regions in the catalyst layer. Results from various MEAs tested in a single cell on a fully automated test station to evaluate catalyst performance will be presented. The evaluation of new catalyst ink recipes with reduced ionomer to carbon ratios is included in this study to further increase mass transport by reducing ionomer swelling in the catalyst layer at high relative humidity. Acknowledgments This research is supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells program manager: Dimitrios Papageorgopoulos. References 1. T. E. Springer, M. S. Wilson, and S. Gottesfeld, J. Electrochem. Soc. , 140 ( 12 ), 3513–3526 (1993). 2. R. Borup and T. Rockward, US Dep. Energy Annu. Merrit Rev., Project ID: FC052 (2015). https://www.hydrogen.energy.gov/pdfs/review15/fc052_rockward_2015_p.pdf Figure 1. Performance of textured and baseline MEA at 275kPa in H 2 /Air @ 80 o C and 100%RH. Figure 1

Qiangu Yan, Qingyun Liu, Junxiao Wu

3rd International Conference on Fuel Cell Science, Engineering and Technology • 2004

Water balance in a polymer electrolyte membrane fuel cell (PEMFC) was investigated by measurements of the net drag coefficient under various conditions. The effects of water balance in the PEM fuel cell on the cell performance were also investigated at different operating conditions. Experimental results reveal that the net drag coefficient of water through the membrane depends on current density and humidification of feed gases. It is found that the net drag coefficient (net number of water molecules transported per proton) has values between 0.93 and −0.015 depending on operating condition, current loading and level of humidification. It was also found that the humidity of both anode and cathode inlet gases had significant effect on fuel cell performance. The results will be used to define conditions of optimal hydration of the membrane. Based on the performance and resistance measurements, optimal humidification can be achieved. The resistance of working fuel cell shows that the membrane resistance increases with the feed gas relative humidity (RH) decreased. Data obtained will be used to evaluate the transport parameters such as net flux of water through the membrane and the effective drag under various operating conditions, and further provide validation data for the fuel cell modeling and simulation efforts.

Wenjuan Bian, Wei Wu, Christopher J. Orme et al.

Advanced Functional Materials • 2020

Abstract Direct carbon fuel cells (DCFCs) are an efficient energy‐conversion technology capable of generating electricity with carbon‐dioxide‐capture chemistry with solid carbon as fuels. The efficiency and performance of DCFCs depend on the kinetics of the carbon oxidation reactions (COR) and the oxygen reduction reactions (ORR), each occurring at anode and cathode, respectively. The limited active sites paired with reduced temperatures greatly decrease the efficiency of the electrochemical reactions. Ultraporous dual‐3D ceramic textiles (dual‐3DCT) are integrated into electrolyte‐supported DCFCs to enhance charge and mass transfer at the electrodes. Improved COR at the anode is achieved by the synergy between the 3DCT NiO–Ce 0.8 Gd 0.2 O 1.95 (GDC) structure and optimal carbon fuel choice. In a comparative study, DCFCs using graphitic carbon (GC) as fuel show the best COR performance when compared to DCFCs utilizing alternative fuels such as carbon black (CB) and activated carbon (AC). The 3DCT Sm 0.5 Sr 0.5 CoO 3‐δ –GDC (SSC–GDC) composite cathode shows electrochemical performance superior to that of the conventional screen‐printed SSC–GDC. A peak power density of 392 mW cm −2 at 600 °C is obtained in a DCFC using the 3DCT‐anode/electrolyte/3DCT‐cathode configuration, an unprecedented value for any reported DCFC as of yet. This points toward promising applications of dual‐3DCT electrodes for reduced‐temperature DCFCs.

Dong Tang, Hui Min Lv, Quan Hui Hou et al.

Advanced Materials Research • 2011

By using the mesocarbon microbead (MCMB) and graphite as raw material, the tubular cathode green bodies of a direct ethanol fuel cell（DEFC）are shaped by the gelcasting technology and the tubular cathode is prepared by spraying the diffusion layer and the Pt/C catalyst layer after the sintering process. Through the tubular cathode physical performance and electrical property test, the advantages and disadvantages of cathode tube performance are studied at different graphite proportion. The results showed that with the increase of graphite, the ratio porosity of cathode tube support body increases at first and then decreases. However, the density has a converse trend. While the maximum porosity of the cathode tube is more than 0.5 and the corresponding density is 0.95g/cm3. Strength test showed that the cathode tube strength is better with the graphite ratio from 0 to 40 percent and can meet the actual needs. Electrical property tests showed that the cathode tube has higher current density with the graphite ratio of 40 and 50 percent.

Luciana Peixoto, Pier Parpot, Gilberto Martins

Energies • 2019

The decentralized production of bioelectricity as well as the bioremediation of contaminated sediments might be achieved by the incorporation of an anode into anaerobic sediments and a cathode suspended in the water column. In this context, a sediment microbial fuel cell microcosm was carried out using different configurations of electrodes and types of materials (carbon and stainless steel). The results showed a long-term continuous production of electricity (>300 days), with a maximum voltage of approximately 100 mV reached after ~30 days of operation. A twofold increase of voltage was noticed with a twofold increase of surface area (~30 mV to ~60 mV vs. 40 cm2 to 80 cm2), while a threefold increase was obtained after the substitution of a carbon anode by one of stainless steel (~20 mV to ~65 mV vs. 40 cm2 to 812 cm2). Cyclic voltammetry was used to evaluate sediment bacteria electroactivity and to determine the kinetic parameters of redox reactions. The voltammetric results showed that redox processes were limited by the diffusion step and corresponded to a quasi-reversible electron charge transfer. These results are encouraging and give important information for the further optimization of sediment microbial fuel cell performance towards the long-term operation of sediment microbial fuel cell devices.

Kaisei Shiraki, Soichiro Hirose, Trang Nakamoto et al.

International Journal of Smart Grid and Clean Energy • 2023

Microbial Fuel Cells (MFCs) are a promising technology that can simultaneously address recent energy shortages and wastewater treatment problems for freshwater production. Recently, inexpensive Pt-free catalysts have been investigated to improve the cathode performance of MFCs. In this study, birnessite manganese oxide intercalated a cobalt (Co-MnO₂) catalyst to make the cathode sterilizable. The use of a bactericidal cathode is expected to improve output by suppressing electron transfer from microorganisms to the cathode, which is the cause of MFC performance degradation, and by eliminating the separator that limits proton transfer. The MFC with Co-MnO₂ catalyst on the cathode achieved a maximum power density of 110 μW/cm². In addition, the function of the Co-MnO₂ catalyst did not degrade for at least 158 days.

Fangming Jiang, Chao-Yang Wang, Ken S. Chen

ASME 2009 7th International Conference on Fuel Cell Science, Engineering and Technology • 2008

Current-ramping strategy can be used for rapid startup of PEM fuel cells (PEMFC) from subzero temperatures. Via numerical modeling a series of parametric studies are performed in this work to explore the optimum parameter set for current-ramping cold-start. A PEMFC with standard cell thermal mass, 0.4 J/cm2/K, starting from −30°C is of primary interest in this work. It is found that either a small initial current density (100mA/cm2) combined with an intermediate ramping rate, or a relatively large initial current density (200 mA/cm2) in combination with a small ramping rate, can lead to successful self-starts if the membrane electrode assembly (MEA) is sufficiently dry prior to startups. However, the current-ramping cold-start with a too small initial current density (≤50mA/cm2) is found to shut down with whatever the current-ramping rate. More rapid self-start can be achieved by increasing the initial current density, which is limited mainly by the initial water content in the MEA. Hence, keeping the MEA mildly hydrated prior to cold start can be favorable to the rapid current-ramping startup. This is particularly important for the rapid startup of next-generation PEMFCs with reduced thermal mass. Results show that a PEMFC with 0.2 J/cm2/K thermal mass and a relatively wetted MEA can be successfully started up from −30°C in a few seconds if it is possible to draw the current density as high as 1 A/cm2 right from the beginning.

Javier Rubio-Garcia, Daniel Malko, Anthony R. J. Kucernak et al.

ECS Meeting Abstracts • 2018

Wastewater streams contain organic molecules that need to be removal before disposal which requires an energy input on average of 6 kWh ton -1 . (1) The fermentation of biomass to produce biogas employs living organisms and permits the valorization of the waste with generation of electricity. However, this technology present limitations in terms of capital cost (ranging USD0.06 and USD0.30 as a function of the size of the digester) and large volume footprint. (2) Microbial fuel cells (MFCs) offer the ability significantly reducing the Chemical Oxygen Demand (COD) contamination is waste water effluents while produce moderate amounts of power. (3) In this contribution, we present the first abiotic waste water fuel cell, a system that directly converts organic materials found in waste sources from different industries into electrical energy. The implementation of inorganic catalysts permits a so-called zero gap design which contributes to minimize the distance between the anode and cathode which is normally large for MFCs to minimize oxygen crossover. This configuration was combined with a commercial PtRu oxidation catalysts produced an unprecedented high power density when using real waste water streams (2.6 mW cm -2 ). Moreover, when operated in a continuous loop COD removals as high as 50% has been achieved. This abiotic system significantly reduces processing time associated to incubation periods which are necessary for bio-processes such as biogas generation. (4) References: (1) United States Environmental Protection Agency, Local Government Climate and Energy Strategy Series ( 2008 ). (2) Weiland et al. , Applied Microbiology and Biotechnology 85, 849-860 ( 2010 ). (3) Liu et al. , Environmental Science & Technology 38, 4040-4046 ( 2004 ). (4) Mao et al., Renewable & Sustainable Energy Reviews 45, 540-555 ( 2015 ).

Alper Can Ince, Wipula Liyanage, Tanvir Alam Arman et al.

ECS Meeting Abstracts • 2024

Abstract Polymer electrolyte membrane fuel cells (PEMFCs) present a promising zero carbon emissions alternative to internal combustion engines. However, PEMFCs face performance limitations, particularly in heavy-duty vehicle applications, largely attributed to cathode electrode inefficiencies. Conventional electrode structures often result in non-ideal tortuous pathways for oxygen (O 2 ) and protons (H + ), leading to decreased performance and durability. In this study, we present a novel hybrid electrode structure fabricated using patterned silicon (Si) templates. These templates, created via photolithography and deep-reactive ion etching, facilitate the formation of ordered plus-shaped electrode structures with uniform depth and width. Catalyst with a different ionomer loading/composition is deposited in-between the element of the plus-shaped electrode structure. The resulting novel arrangement in the hybrid electrode structure enables enhanced H + transport, due to the higher ionomer content in the plus-shaped electrode structures. Additionally, strategically placed dedicated electrode regions with lower ionomer content between the plus shaped electrodes promotes effective O 2 transport to reaction sites. We will present the fabrication process, the performance enhancement through this alternative electrode structure and its contribution to the improving the durability of the fuel cells compared to conventional electrode architectures. Acknowledgement This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (20200200DR).

Levent Akyalçın

Chemical Industry and Chemical Engineering Quarterly • 2018

In this study, Taguchi?s experimental design is used to determine the optimum component combination of a membrane electrode assembly and cathode current collector opening geometry to obtain maximum power density of an airbreathing polymer electrolyte membrane fuel cell at 0.5 V. An analysis of variance was conducted to figure out the optimum levels and significant differences of the effect of the combinations, followed by a performance measurement analysis. Experimental investigations of the effecting parameters enabled the determination of the optimum configuration of the MEA and cathode current collector opening geometry design parameters for maximum power density at a certain cell potential. Effective parameters which enable withdrawal of a maximum power output from an ABPEMFC at 0.5 V are, in order of effectiveness: the amount of platinum on the cathode, the thickness of the Nafion membrane, the cathode current collector opening geometry, and the amount of platinum on the anode. Optimum component combinations are: 0.45 mgPt cm?2 for the platinum loading on the cathode, Nafion 112 for membrane, a vertical cathode opening geometry and 1.78 mg cm?2 for the amount of platinum on the anode. For these component combinations, a 98.5 mW cm?2 power output was obtained from an ABPEMFC at 0.5 V cell voltage.

Rehab H. Mahmoud, Farag A. Samhan, Mohamed K. Ibrahim et al.

Electrochemical Science Advances • 2020

Abstract Production of bioelectricity via microbial fuel cells (MFCs) may become an important source of energy in the near future due to the possibility of extracting electric current from a wide range of organic wastes. In this study, several nanostructures, such as platinum (Pt)‐reduced graphene oxide nanocomposite, graphene nanosheets, MnO 2 , and MnO 2 /RGO, were synthesized, characterized, and investigated as cathode catalysts for oxygen reduction reaction. The prepared catalysts were tested in a single‐chamber microbial fuel cell with anaerobic bacterial mixed culture. Power density produced from MFC closed circuit operation using the nanoengineered catalysts were about 68 times more than those obtained using the classical graphite electrodes. Moreover, there was a slight reduction of 5.8% in power density (from 170 to 160 mW/m 2 ) when Pt nanoparticles were loaded on the RGO nanosheets compared to Pt/C cathode. By replacing the precious Pt catalyst with other nanomaterials, a significant reduction in power density was observed. For RGO‐based cathode, the MFC performance decreased by 31.1% (from 170 to 117 mW/m 2 ) and the percent of reduction reached 48.5% (from 170 to 88 mW/m 2 ) for MnO 2 ‐based cathode MFC. However, in RGO/MnO 2 nanocomposite cathode MFC, the percent of reduction in power density was 26.4% (from 170 to 125 mW/m 2 ). It can be concluded that RGO nanosheets loaded with Pt nanoparticles is a starting point for finding an alternative economic and effective cathode.

Anastasia Dmitrieva, Elizaveta Faskhutdinova, Timothy Larichev et al.

Food Processing: Techniques and Technology • 2024

Traditional energy sources pollute the environment. Microbial fuel cells are an alternative energy source that can reduce the environmental burden. Microbial fuel cells also remove recalcitrant wastes from wastewater. This research featured the enzymatic potential of microbial isolates obtained from the Abakan Arzhan thermal spring. The study involved isolates of the genera Geobacter, Thermomonas, and Rhodopseudomonas. The keratinolytic analysis was in line with State Standard R 55987-2014. The chitinolytic activity was determined by injecting a bacterial suspension on Petri dishes with a chitin-containing medium. The lipolytic analysis involved cultivating the isolates in Stern’s glycerol fuchsin broth. The xylan hydrolysis depended on the reducing sugars. The cellulase activity was measured according to the standard method recom mended by the International Union of Pure and Applied Chemistry (IUPAC). The catalase potential was evaluated by the gasometric method on 1% gasoline media. The optimal parameters of consortium cultivation were determined by the voltage generated. The Geobacter isolate had the maximal keratinolytic activity while the Thermomonas isolate demonstrated the maximal protein hydrolysis (80.1 ± 1.5%). Both Geobacter and Rhodopseudomonas showed good lytic activity against chitin with the lysis zone of ≥ 3 mm. The Geobacter isolate demonstrated as many as 350 units of xylanase activity and 365 units of cellulase activity; Ther momonas had 350 units of xylanase activity and 360 units of cellulase activity; Rhodopseudomonas showed 310 units of xylanase activity and 304 units of cellulase activity. The maximal catalase properties belonged to Geobacter (1.40 units) and Thermomonas (1.38 units). The maximal energy generation by bacterial consortia occurred at pH 8 and 45°C after 48 h of cultivation. In this research, isolates of the genera Geobacter, Thermomonas, and Rhodopseudomonas from the Abakan Arzhan thermal spring were able to remove recalcitrant components, thus demonstrating good prospects for biological treatment of industrial wastewater.

Guido Bender, Adam Phillips, Jocelyn Mackay et al.

ECS Meeting Abstracts • 2016

Polymer electrolyte membrane fuel cells (PEMFCs) are energy conversion devices that offer high power densities at low operating temperatures making PEMFCs the most promising technology for many applications such as automobiles, back-up power generating units, and portable devices. While design and material considerations for PEMFCs have a large impact on cost, it is also necessary to consider a transition to high volume production of fuel cell systems, including MEA components, to enable economies of scale and reduce per-unit cost. The fuel cell industry has identified quality control as a critical barrier for continuous production of MEA components, i.e. membranes, electrodes, and GDLs. One of the critical manufacturing tasks is developing and deploying techniques to provide in-process measurement of fuel cell components for quality control. This work focuses on a necessary subsidiary task: The study of the effect of manufacturing irregularities on performance with the objective to establish validated manufacturing tolerances for fuel cell electrodes. Membrane electrode assemblies with nominal active areas of 50 cm 2 were prepared by spraying a catalyst ink formulation directly onto NRE212 polymer membrane material held at 80°C. The spray system was an ExactaCoat from Sono-Tek with an ultrasonic spray head. Catalyst loading variations were created by masking off 0.0625 – 1 cm 2 areas. Within the defect area the nominal catalyst loading was reduced by various degrees up to 100% of the nominal value. The sample pool includes MEAs with different locations, shapes, and severity of coating irregularities, different nominal loading, as well as CCM vs. GDE structures. For spatial interrogation NREL’s high resolution segmented cell system was employed. The system consists of 121 segments of 0.41 cm 2 area each arranged along the path of a quadruple serpentine flow-field. The segmented cell system was operated with a state-of-the-art single cell fuel cell test station. Figure 1 shows one sample set used to understand the performance effect of reducing total catalyst loading by 1% of the nominal loading. Rather than reducing catalyst loading in a single location only, variations of the 1% reduction were introduced to investigate if (i) location, (ii) shape, and (iii) intensity of the 1% coating variation matter. Differential spatial data was computed by subtracting the current distribution measured with a sample MEA from that of a pristine MEA. Figure 2 shows two such differential data sets. Areas with reduced performance are red, those with increased performance are blue, and those with unchanged performance are black. The data shows results for a sample with 2x 0.25 cm 2 coating variations each having a 100% loading reduction, one near the inlet and one near the outlet (left) and for a second sample with a 1 cm 2 50% reduction coating variation in the center. In addition, Figure 3 shows the total cell performance of the sample set. The total cell performance alone, as shown in Figure 3, does not indicate the presence of the defect. Instead, the detection of the impact of the defect requires a high resolution spatial diagnostic tool. As shown in Figure 2, the effect of the defect fades when reducing defect size. The areas that are 0.25 cm 2 and have no catalyst loading show a smaller performance impact than the 1 cm 2 area that only has a loading reduction of 50%. Obviously the impact of the coating variation has been distributed to more than one location. In any case, with respect to the total cell performance impact, the coating variation may not be classified as a defect, since no impact has been detected. A second criteria to classify the studied coating variation as defects is the effect on lifetime. These studies are currently underway and will be addressed in a second presentation. Figure 1

Feng Li, Changji Yin, Liming Sun et al.

Biotechnology Journal • 2017

Microbial fuel cell (MFC) is an eco‐friendly bio‐electrochemical sys­tem that uses microorganism as biocatalyst to convert biomass into electricity. Glycerol, as a waste in the biodiesel refinery processes, is an appealing substrate for MFC. Nevertheless, glycerol cannot be utilized as carbon source by well‐known exoelectrogens such as Shewanella oneidensis . Herein, to generate electricity by rapidly harnessing glycerol, the authors rationally constructed a Klebsiella pneumoniae ‐ Shewanella oneidensis microbial consortium to efficiently harvest electricity from glyc­erol, in which K. pneumoniae converted glycerol into lactate, fed to S. oneidensis as carbon source and electron donor. To improve electricity output, the authors systematically engineered the consortium in terms of carbon flux distribution and efficiency of extracellular electron transfer (EET). To direct more carbon flux to lactate biosynthesis in K. pneumoniae , the authors eliminated the ethanol pathway by knocking out the alcohol dehydrogenase gene ( adhE ), and enhanced lactate biosynthesis by heterologously expressing a lactate dehydrogen­ase gene ( ldhD ) from Lactobacillus bulgaricus and a lactate transporter gene ( lldP ) from Escherichia coli . To facilitate EET between S. oneidensis and anode surfaces, a biosynthetic flavins pathway from Bacillus subtilis is introduced into S. oneidensis . The author further optimized the glycerol concentration, thus S. oneidensis could be continuously fed with lactate synthesized from K. pneumoniae at a constant rate. Our glycerol‐fed MFC generated a maximum power density of 19.9 mW/m 2 , significantly higher than that of the wild‐type consor­tium. This work suggested that engineering microbial consortia is an effi­cient strategy to expand the spectrum of usable carbon sources and promote electricity power production in MFCs.

Arezou Mohseninia, Dena Kartouzian, Fabian Regnet et al.

ECS Meeting Abstracts • 2018

The water inventory of PEMFC components strongly influences the performance under two-phase operating conditions. Within this work, the influence of hydrophobicity variation within electrode and microporous layer (MPL) on cell performance will be presented. Different weight percentages of PTFE is used in the catalyst and MPL inks as an additive in order to increase the hydrophobicity. The fabrication method for the membrane electrode assembly (MEA) is based on spraying the catalyst ink onto the membrane and coating MPL ink onto the GDL substrate using a doctor blade method. Fuel cell tests are carried out with a 25 cm² active area single cell at different relative humidities (RH) and oxygen flow rates to investigate the effect of PTFE on the ability of MEA and MPL on water management. Electrochemical impedance spectroscopy is performed as a diagnostic tool to investigate the reaction kinetics and mass transport. In order to assess the wettability of MEAs contact angle measurements were carried out. The materials are characterized by mercury porosimetry and scanning electron microscopy. Figure 1 shows the performance curve for cell 1 (conventional MEA +Conventional MPL), cell 2( MEA with 5 wt.% PTFE +Conventional MPL) and cell 3 (Conventional MEA+ MPL with 40 wt.% PTFE ) at different relative humidities. At dry conditions (RH=70%) cell 2 has a higher limiting current density compared to the other cells, which could be the indication that the hydrophobic electrode keeps the membrane material in the catalyst layer better hydrated. At over humidified conditions (RH=120%) the limiting current density value has decreased for cell 1 and 2 compared to the standard conditions (RH=100%) as a result of mass transport limitations. On contrary, Cell 3 shows an improved performance in high current density region at humid conditions, illustrating the ability of hydrophobic MPL to prevent the accumulation of liquid water at the interphase of MPL and catalyst layer at cathode side. In the presentation of the ongoing work, additional results, including HFR data will be reported. Figure 1

Cheng He, Ami C. Yang-Neyerlin, Bryan S. Pivovar

ECS Meeting Abstracts • 2020

AEMFCs as an alternative to acidic polymer electrolyte fuel cells have the potential to reduce cost and precious metal requirements of fuel cell systems. 1 In the past decade, several highly conductive polymers have been developed and a number of these have demonstrated more than 1W∙cm -2 peak power density with hundreds of hours stability; however, most of these studies have focused on Pt containing cathodes with high loadings. 2,3 While the promise of Pt and Pt group metal (PGM) free electrocatalysis has been a major selling point of AEMFCs, more work exploring the potential of PGM-free cathode electrocatalysis is needed. In this study we explore and compare the performance of three leading cathode electrocatalysts: Pt/C, Ag/C, and Fe-N-C. These electrocatalysts are tested in AEMFCs cathodes using both powder- and dispersion-based PF AEM Gen 2 ionomers. 4 The ability to test the different catalyst and ionomer combinations leads to additional insight into performance and catalyst-ionomer interactions. The performance trends of the tested MEAs will be presented. Pt/C has been found to be slightly superior to the performance of the non-Pt electrocatalysts. The performance of both metal nanoparticle catalysts, Pt/C and Ag/C, exhibit strong differences in performance depending on whether or not a powder or dispersion-based ionomer is used, with the powder-based approach showing much higher performance. Unlike the metal electrocatalysts, Fe-N-C catalysts show almost no change of performance between powder and dispersion-based ionomers. These performance metrics are also reflected in high frequency resistance measurements (Figure 1) investigated as a function of relative humidity at 300 mA·cm - 2 . This data clearly shows the expected trend of increasing HFR with decreasing humidification of reactant gasses. The Fe-N-C data shows the lowest HFR values and very small changes between powder and dispersion-based ionomers. Both, Pt/C and Ag/C show dramatic increases in HFR for the dispersion-based polymer compared to the powder-based ionomer. These large changes in HFR are unexpected and cannot be fully explained just by changes happening within the electrodes. They suggest that not only do the electrodes undergo variable electrochemical properties due to this processing, but water management within the cell is also impacted by the type of catalyst and ionomer used in processing the electrodes. These features and the impact they have on the performance of different AEMFC cathodes will be presented and discussed. References: S. T. Thompson, D. Peterson, D. Ho and D. Papageorgopoulos, Journal of The Electrochemical Society , 167 (2020). S. Maurya, S. Noh, I. Matanovic, E. J. Park, C. Narvaez Villarrubia, U. Martinez, J. Han, C. Bae and Y. S. Kim, Energy & Environmental Science , 11 , 3283 (2018). T. J. Omasta, L. Wang, X. Peng, C. A. Lewis, J. R. Varcoe and W. E. Mustain, Journal of Power Sources , 375 , 205 (2018). A. M. Park, Z. R. Owczarczyk, L. E. Garner, A. C. Yang-Neyerlin, H. Long, C. M. Antunes, M. R. Sturgeon, M. J. Lindell, S. J. Hamrock, M. Yandrasits and B. S. Pivovar, ECS Transactions , 80 , 957 (2017). Figure 1

Gregory J. Newton, Shigeki Mori, Ryuhei Nakamura et al.

Applied and Environmental Microbiology • 2009

ABSTRACT Although members of the genus Shewanella have common features (e.g., the presence of decaheme c -type cytochromes [ c -cyts]), they are widely variable in genetic and physiological features. The present study compared the current-generating ability of S. loihica PV-4 in microbial fuel cells (MFCs) with that of well-characterized S. oneidensis MR-1 and examined the roles of c -cyts in extracellular electron transfer. We found that strains PV-4 and MR-1 exhibited notable differences in current-generating mechanisms. While the MR-1 MFCs maintained a constant current density over time, the PV-4 MFCs continued to increase in current density and finally surpassed the MR-1 MFCs. Coulombic efficiencies reached 26% in the PV-4 MFC but 16% in the MR-1 MFCs. Although both organisms produced quinone-like compounds, anode exchange experiments showed that anode-attached cells of PV-4 produced sevenfold more current than planktonic cells in the same chamber, while planktonic cells of MR-1 produced twice the current of the anode-attached cells. Examination of the genome sequence indicated that PV-4 has more c -cyt genes in the metal reductase-containing locus than MR-1. Mutational analysis revealed that PV-4 relied predominantly on a homologue of the decaheme c -cyt MtrC in MR-1 for current generation, even though it also possesses two homologues of the decaheme c -cyt OmcA in MR-1. These results suggest that current generation in a PV-4 MFC is in large part accomplished by anode-attached cells, in which the MtrC homologue constitutes the main path of electrons toward the anode.

Abdullah Almatouq, Gordon Webster, Akintunde Babatunde

Journal of Chemical Technology & Biotechnology • 2022

Abstract Background Silver (Ag) removal, electric current generation and the microbial community responsible were investigated in two replicate dual‐chamber microbial fuel cells (MFCs). The MFCs were inoculated with activated sludge and operated for electricity generation over 90 days. Results Silver was efficiently removed from synthetic wastewater at the cathode chamber of the MFC and the precipitated particles on the cathode electrode were verified as Ag using X‐ray diffraction and scanning electron microscopy analysis. The MFCs achieved a maximum power density of 1850 ± 25 mW m −2 and a maximum Ag removal of 99.8%. Furthermore, Illumina high‐throughput sequencing of bacterial 16S rRNA genes showed that both MFCs shared the same dominant bacterial phyla, namely Synergistetes, Bacteroidetes, Proteobacteria and Firmicutes, with bacteria belonging to Butyricicoccus , Petrimonas , Desulfomicrobium and Desulfovibrio and large numbers of unassigned genera. Conclusions The dual‐chamber MFCs provided an efficient method for concurrent Ag removal and energy generation, and effectively removed and recovered Ag from various wastewater streams even at low Ag concentrations. However, continued Ag precipitation on the electrode surface during long‐term operation could lead to a deterioration in the performance of the MFC and an increase in internal resistance. © 2022 Society of Chemical Industry (SCI).

Benjamin Gould, Yannick Garsany, Megan Sassin et al.

Materials Science Forum • 2018

Gas diffusion media (GDM) is an integral part of all gas diffusion electrodes because it facilitates both the transport of reactants to the electrocatalyst surface and the removal of reaction products from the system. Proper reactant/product distribution is critical for high power operation in polymer electrolyte fuel cells (PEMFCs) because oxygen transport and water rejection determine the maximum current density that can be obtained from PEMFCs. This paper will discuss NRL’s research on how GDM morphology influences cell performance in both closed-cathode fuel cell and open-cathode fuel cell designs. The comprehensive study linking the influence of compression on the GDM micro and macro structure morphology will be presented using micro X-ray computed tomography (μ-CT), scanning electron microscopy (SEM), N 2 Physisorption (BET) and traditional electrochemical characterization techniques (CV, Pol. Curves, etc.). Optimal GDM selection for the challenge of open-cathode operation will be presented and related to water retention through rational morphology selection. The relationship between high power performance and water transport will be elucidated and the goals for future GDM properties will be proposed for use in unmanned systems

Van Lap Nguyen, Agnesia Permatasari, Magnus So et al.

ECS Meeting Abstracts • 2024

The Polymer electrolyte fuel cell (PEFC) is a promising technology for power generation, noted for its potential as a zero-carbon technology at the point of use. However, PEMFC faces challenges that must be addressed to enhance its viability, such as its high cost and inefficient output power density. A key component influencing these factors is the cathode catalyst layer (CCL), which is critical for the mass transport flux and electrochemical reactions within the fuel cell. A strategy to lower costs while maintaining performance involves optimizing the CCL composition, including the ionomer-to-carbon (I/C) ratio, Pt-to-carbon (Pt/C) ratio, CCL thickness, and the type of carbon black used, alongside minimizing the Pt loading. Such optimization involves consideration of multiple factors and, consequently, adjusting the CCL composition might have a high potential to balance cost and performance. In this study, therefore, our goal is to propose an optimized catalyst composition that enables high-cell performance with low Pt loading. In particular, we integrated a surrogate machine learning model with an optimization algorithm to determine the optimization of CCL composition. The composition of each CCL is characterized by several variables, including the Pt/C and I/C, the thickness of the catalyst layer, the ionomer coating condition (uniform and non-uniform coatings), and the type of carbon used, which varied between porous (Ketjen) and non-porous (Vulcan) carbon [1]. These variables and output power density were assigned as input and output variables of the machine learning models, respectively. The dataset for the machine learning model was prepared by conducting cell performances with various CCL compositions by the multi-block method detailed in our previous work [2,3]. A total of 390 simulations were used as the dataset, with 312 data points used for training and 78 data points for testing. An assembled machine-learning algorithm known as Extreme Gradient Boosting (XGB) was employed to develop the surrogate model. To identify the optimal CCL composition that generates the highest output power density at a given Pt loading, the XGB-based surrogate model was integrated with an optimization algorithm based on the genetic algorithm (GA). In particular, the fitness of each individual within the GA population is determined by the XGB-based surrogate model, and the GA iteratively evaluates the fitness using operations such as selection, crossover, and mutation, to converge toward the composition that results in the highest power density. The performance of the XGB-based surrogate model in predicting cell performance is validated by its root mean squared error (RMSE) and square correlation coefficient (R²) on the test set, which are 0.07 and 0.89, respectively. This means the cell performance can be predicted by the surrogate model. In the importance feature analysis, the I/C ratio, carbon type, and thickness were identified as the most important parameters of CCL structures. This suggests that we can reduce the Pt load by optimizing the I/C ratio, CCL thickness, and type of carbon black. From the GA results, an optimal starting Pt loading of 0.25 mg/cm² was refined by adjusting the I/C ratio to 0.95, selecting Vulcan as the carbon type, and setting the CCL thickness to 6.54 µm. Through optimization, the Pt load was successfully reduced to 0.198 mg/cm², while maintaining the same power density as the initial loading of 0.25 mg/cm². This outcome highlights the efficacy of the surrogate model and optimization approach in enhancing the cost-efficiency of PEMFCs without compromising their performance. Acknowledgments This research was supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan (grant number P20003-20001327-0). References: [1] K. Park et al., J. Power Sources Advances, 2022, 15,100096 [2] G. Inoue et al., J. Power Sources 2019 439, 227060 [3] G Inoue et al., Int. J. Hydrogen Energy 2022, 47 (25), 12665