Xiangyu Chen, Benyi Xiao, Xinyi Tang et al.

Chemosphere • 2022

The effects of microbial electrolysis cells (MECs) at three applied voltages (0.8, 1.3, and 1.6 V) on simultaneously enhancing methanization and reducing hydrogen sulfide (H2S) production in the anaerobic digestion (AD) of sewage sludge were studied. The results showed that the MECs at 1.3 V and 1.6 V simultaneously enhanced the methane production by 57.02 and 12.70% and organic matter removal by 38.77 and 11.13%, and reduced H2S production by 94.8 and 98.2%, respectively. MECs at 1.3 V and 1.6 V created a micro-aerobic conditions for the digesters with oxidation-reduction potential as -178∼-232 mv, which enhanced methanization and reduced H2S production. Sulfur reduction, H2S and elemental sulfur oxidation occurred simultaneously in the ADs at 1.3 V and 1.6 V. The relative abundances of sulfur-oxidizing bacteria increased from 0.11% to 0.42% and those of sulfur-reducing bacteria decreased from 1.24% to 0.33% when the applied voltage of MEC increased from 0 V to 1.6 V. Hydrogen produced by electrolysis enhanced the abundance of Methanobacterium and changed the methanogenesis pathway.

Wanjun Cui, Yaobin Lu, Cuiping Zeng et al.

The Science of the total environment • 2020

The aim of this study was to investigate the performance of single-chamber MEC under applied voltages higher than that for water electrolysis. With different acetate concentrations (1.0-2.0 g/L), the MEC was tested under applied voltages from 0.8 to 2.2 V within 2600 h (54 cycles). Results showed that the MEC was stably operated for the first time within 20 cycles under 2.0 and 2.2 V, compared with the control MEC with significant water electrolysis. The maximum current density reached 27.8 ± 1.4 A/m2 under 2.0 V, which was about three times as that under 0.8 V. The anode potential in the MEC could be kept at 0.832 ± 0.110 V (vs. Ag/AgCl) under 2.2 V, thus without water electrolysis in the MEC. High applied voltage of 1.6 V combined with alkaline solution (pH = 11.2) could result in high hydrogen production and high current density. The maximum current density of MEC at 1.6 V and pH = 11.2 reached 42.0 ± 10.0 A/m2, which was 1.85 times as that at 1.6 V and pH = 7.0. The average hydrogen content reached 97.2% of the total biogas throughout all the cycles, indicating that the methanogenesis was successfully inhibited in the MEC at 1.6 V and pH = 11.2. With high hydrogen production rate and current density, the size and investment of MEC could be significantly reduced under high applied voltages. Our results should be useful for extending the range of applied voltages in the MEC.

Wanjun Cui, Haiping Luo, Guangli Liu

Waste management (New York, N.Y.) • 2023

Hydrogen production from food waste is of great significance for energy conversion and pollution control. The aim of this study was to investigate the glucose fermentation from food waste and hydrogen (H2) production in the single-chamber microbial electrolysis cell (MEC) under hyperalkaline conditions. Single-chamber MECs were tested with 1 g/L glucose as substrate under different pH values (i.e., 7.0, 9.5, and 11.2) and applied voltages (i.e., 0.8, 1.2, and 1.6 V). With pH increase from 7.0 to 11.2, H2 production with methanogenesis inhibition was significantly improved in the MEC. At pH of 11.2, the maximum current density reached 180 ± 9 A/m3 with the H2 purity of 93.3 ± 1.2% and average H2 yield of 7.72 ± 0.23 mol H2/ mol glucose under 1.6 V. Acetate from glucose fermentation was the largest electron sink within 12 h. Methanobacterium alcaliphilum dominated the archaeal communities with the relative abundance of > 99.0% in the cathodic biofilms. The microbial communities and mcr A gene copy numbers analyses showed that high pH enhanced the acetate production from glucose fermentation, inhibited syntrophic acetate-oxidizing with hydrogenotrophic methanogenesis in the anodic biofilms, and inhibited hydrogenotrophic methanogenesis in the cathodic biofilms. Our results of hyperalkaline conditions provide a feasible way to harvest H2 efficiently from fermentable substrates in the single-chamber MEC.

Qiongli Shao, Jianchang Li, Sixia Yang et al.

Water Science and Technology • 2019

Abstract To investigate the effects of different substrates on the biodiversity and hydrogen production performance of microbial electrolysis cell (MEC) anodic membranes, the vital electroactive microorganisms (e.g. in MEC hydrogen production) were worth identifying. In the present study, single-factor experiments were performed. Sodium acetate, sodium propionate, sodium butyrate, glucose and starch served as different substrates for MEC anodic culture experiments under the same condition. The effects of different substrates on the bioactivity, biomass and hydrogen production performance of MEC anodic films were analyzed. Also, the effects of different microbial communities on hydrogen production were studied using 16S rRNA sequencing. According to the experimental results, all the five substrates here can serve as hydrogen-producing raw materials for MEC. All indicators revealed that sodium acetate, sodium propionate and sodium butyrate are excellent biofilm culture materials. The serious acidification of glucose and starch was identified at the same substrate concentration, and the environment of the culture medium was difficult to control, which affected the growth and metabolism of electroactive microorganisms. In comparison, sodium acetate was the best, achieving a maximum output of 23.4 mA and a maximum hydrogen content of 25.85%. The other four were ranked as sodium butyrate > sodium propionate > glucose > starch. According to the results of high-throughput sequencing, when sodium acetate, sodium propionate, sodium butyrate, glucose and starch served as substrates, the number of operational taxonomic units reached 464, 728, 636, 784, and 1,083, respectively. Furthermore, when MEC was cultured with sodium acetate, sodium propionate and sodium butyrate as substrates, the electroactive microorganism Desulfuromonas in the Proteobacteria would contribute the most to producing hydrogen. The relative abundance of the five substrates was ranked as sodium acetate > sodium butyrate > sodium propionate > glucose > starch, suggesting that the MEC anodic film cultured with sodium acetate as the substrate exhibited the best hydrogen production performance, and the starch showed the worst. It is noteworthy that Desulfuromonas was the most abundant species according to sequencing results. When glucose and starch served as substrates, they exhibited high biodiversity. The anodic membranes cultured with sodium acetate, sodium propionate and sodium butyrate were not as good as those cultured with glucose and starch, yet the electroactive microorganisms were up-regulated.

Rukayya Ibrahim Muazu, Jhuma Sadhukhan, S Venkata Mohan et al.

Environmental science : water research & technology • 2023

Bioelectrochemical systems (BESs) such as microbial fuel cells (MFCs) present numerous benefits for the removal and recovery of heavy metals from industrial and municipal wastewater. This study evaluated the life cycle environmental impact of simultaneous hexavalent chromium (Cr(vi)) removal and bioelectricity generation in a dual chamber MFC. Results indicate a global warming potential (GWP) of -0.44 kg carbon dioxide (CO2)-eq. per kg of chromium recovered, representing a total saving of up to 97% in comparison with existing technologies for the treatment of Cr(vi) laden wastewater. The observed savings in GWP (kg CO2-eq.) reduced to 61.8% with the removal of the allocated credits from the MFC system's life cycle. Of all the various sub-systems considered within the chromium waste treatment plant, the MFC unit and the chromium metal recovery unit had the largest impact in terms of GWP (kg CO2-eq.), non-renewable energy use (NREU) (MJ primary), and mineral extraction (MJ surplus). A statistical analysis of the results showed that an increase in chemical oxygen demand (COD) was associated with a reduction in GWP (kg CO2-eq.), NREU (MJ primary), and terrestrial ecotoxicity (kg triethylene glycol equivalents into soil (TEG soil)-eq.). The life cycle assessment (LCA) output showed a high sensitivity to changes in the materials and construction processes of MFC reactors, indicating the need for further research into sustainable materials for MFC reactor construction. The observed interaction effects of process variables also suggest the need for combined optimization of these variables. Analysis with other types of metals is also important to further demonstrate the practical viability of metal removal through MFCs.

Hui-Xiang Wang, Qi-Wei Peng, Yu-Li Yang et al.

Bioresource technology • 2023

Microbial degradation plays a crucial role in removing sulfonamides from soil, enhancing sulfamethoxazole (SMX) remediation. To further augment SMX removal efficiency and mitigate the transmission risk associated with antibiotic resistance genes (ARGs), this study proposes a novel approach that integrates micro-animals, microorganisms, and microbial fuel cell (MFC) technology. The results showed that earthworm-MFC synergy substantially reduces SMX content and ARGs abundance in soil. The introduction of earthworms enhances humus content, facilitating electron transfer within MFC and consequently improving current generation. Furthermore, electrical stimulation applied to earthworms led to increased protein secretion and enhanced antioxidant system activity, thereby accelerating SMX degradation. Earthworms also foster MFC-associated bacterial growth and SMX-degrading bacteria proliferation, augmenting MFC treatment efficacy. This synergistic effect significantly augmented the overall efficacy of MFC treatment for antibiotics. Overall, integrating earthworm activity with MFC technology effectively optimizes electricity generation and enhances pollutant removal.

Shafeer Kalathil, Deepak Pant

RSC Advances • 2015

Advanced nanostructured electrode materials largely improve the bacterial bidirectional extracellular electron transfer in bioelectrochemical systems.

Albert Vilà-Rovira, Sebastià Puig, M. Dolors Balaguer et al.

RSC Advances • 2014

This study assesses the hydrodynamics in the anode compartment of a bioelectrochemical system (BES) when using different electrode materials (graphite rod, granular graphite, stainless steel mesh or graphite plate).

Nicolas Plumeré

ECS Meeting Abstracts • 2019

Redox hydrogel films are among the most practical approaches for protecting O2-sensitive biocatalysts such as hydrogenases from O2 inactivation in bioelectrochemical devices (1). Their protection mechanism relies on the viologen catalyzed reduction of O2 with electrons diverted from the hydrogenase catalyzed H2 oxidation. Despite multiple example of the versatility and universal applicability of the concept (1-3), numerous key question related to their practical use remain open. The lecture will cover unresolved points related to (i) the generation of reactive oxygen species, (ii) the use of excessive thicknesses to ensure protection as well as (iii) the elusive direct evidence for the protection mechanism. Recent progress in the ability to form films with controlled thicknesses (4) and the use of confocal fluorescence microscopy led to new exciting insights in these systems. (1) N. Plumeré, O. Rüdiger, A. Alsheikh Oughli, R. Williams, J. Vivekananthan, S. Pöller, W. Schuhmann, W. Lubitz, Nature Chemistry, 2014, 6, 822–827. (2) V. Fourmond, S. Stapf, H. Li, D. Buesen, J. Birrell, O. Rüdiger, W. Lubitz, W. Schuhmann, N. Plumeré, C. Léger, J. Am. Chem. Soc., 2015, 137, 5494-5505. (3) A. Alsheikh Oughli, F. Conzuelo, M. Winkler, T. Happe, W. Lubitz, W. Schuhmann, O. Rüdiger, N. Plumeré, Angew. Chem. Int. Ed., 2015, 54, 12329 –12333. (4) H. Li, D. Buesen, R Williams, J. Henig, S. Stapf, K. Mukherjee, E. Freier, W. Lubitz, M. Winkler, T. Happe, N. Plumeré, Chemical Science, 2018, 9, 7596-7605. Financial support by the Cluster of Excellence RESOLV (EXC 1069), by the ERC starting grant 715900 and by the ANR-DFG project SHIELDS (PL 746/2-1) is gratefully acknowledged.

V Tholia, B Neethu, G D Bhowmick et al.

Applied biochemistry and biotechnology • 2020

Formation of methane in the anodic chamber of a microbial fuel cell (MFC) indicates an energy inefficiency in electricity generation as the energy required for electrogenesis gets redirected to methanogenesis. The hypothesis of this research is that inhibition of methanogenesis in the mixed anaerobic anodic inoculum is associated with an enhanced activity of the electrogenic bacterial consortia. Hence, the primary objective of this investigation is to evaluate the ability of chloroform to inhibit the methanogenesis at different dosing to enhance the activity of electrogenic consortia in MFC. A higher methane inhibition and hence an enhanced performance of MFC was achieved when mixed anaerobic sludge, collected from septic tank, was used as inoculum after pre-treatment with 0.25% (v/v) chloroform dosing (MFC-0.25CF). The MFC-0.25CF attained a maximum power density of 8.51 W/m3, which was more than twice as that of MFC inoculated with untreated sludge. Also, a clear correlation between the chloroform dosing, methane inhibition, wastewater treatment, and power generation was established, which demonstrated the effectiveness of the technique in enhancing power generation in MFC along with adequate biodegradation of organic matter present in wastewater at an optimum chloroform dosing of 0.25% (v/v) to inhibit methanogenesis.

Arti Sharma, Meenu Chhabra

Bioresource technology • 2020

This study reports the use of Chlamydomonas reinhardtiiat the cathode in a photosynthetic microbial fuel cell (PMFC). The PMFC produced power and current density of 15.21 W m-3 and 39 A m-3, respectively. The specific growth rate of algae culture at the cathode was 0.284 day-1. The system achieved COD removal at 73.30% with a Coulombic efficiency of 9.068%. The usability of algae biomass was assessed in terms of its total phenol content (157.69 mg GAE/g algae DW), antioxidant activity (IC50 = 67.07 µg/ml), total Chlorophyll (18.95 mg/g), total Carotenoids (2.40 mg/g), and antibacterial properties against known pathogens. Overall, the study's findings suggested thatC. reinhardtiisupports high power output from a PMFC and is highly resourceful in terms of value-added products.

Guangyi Zhang, Danxin Liang, Zisheng Zhao et al.

Environmental research • 2022

Tetracycline hydrochloride (TCH) is a typical antibiotic pollutant with high toxicity and persistence. The degradation of TCH and the generation of the associated electron mediator in a dual chamber microbial fuel cells (MFCs) were studied. The results of liquid chromatography revealed that TCH could be effectively removed (>93%) in MFCs mode. The maximum COD removal was 88.14 ± 1.47% in MFCs while it was 69.57 ± 1.36% in open circuit MFCs. According to cyclic voltammetry, the presence of the relevant redox peaks clearly suggested that the intermediates from TCH degradation could act as endogenous electron mediator. The highest power density of 120.02 ± 2.76 mW/m2 and the lowest internal resistance of 18.68 Ω were achieved in MFC with 2 mg/L of TCH. Microbial community analysis illustrated that Bacteroides, Comamonas, Clostridium_sensu_stricto, Desulfovibrio and Geobacter were enriched and played a dominant role in TCH degradation and power generation. Electrochemical active bacteria had certain tolerance to TCH and the inhibiting threshold value of TCH was below 5 mg/L. This study provided a new thinking that low concentration of TCH could produce electron mediators to improve the performance of MFC system.

Huang Jingyu, Nicholas Miwornunyuie, David Ewusi-Mensah et al.

Water science and technology : a journal of the International Association on Water Pollution Research • 2019

Constructed wetland coupled microbial fuel cell (CW-MFC) systems integrate an aerobic zone and an anaerobic zone to treat wastewater and to generate bioenergy. The concept evolves based on the principles of constructed wetlands and plant MFC (one form of photosynthetic MFC) technologies, of which all contain plants. CW-MFC have been used in a wide range of application since their introduction in 2012 for wastewater treatment and electricity generation. However, there are few reports on the individual components and their performance on CW-MFC efficiency. The performance and efficiency of this technology are significantly influenced by several factors such as the organic load and sewage composition, hydraulic retention time, cathode dissolved oxygen, electrode materials and wetland plants. This paper reviews the influence of the macrophyte (wetland plants) component, substrate material, microorganisms, electrode material and hydraulic retention time (HRT) on CW-MFC performance in wastewater treatment and electricity generation. The study assesses the relationship between these parameters and discusses progress in the development of this integrated system to date.

Minh Hang Do, Huu Hao Ngo, Wenshan Guo et al.

The Science of the total environment • 2021

This research explores the possibilities of a dual-chamber microbial fuel cell as a biosensor to measure Bisphenol A (BPA) in wastewater. BPA is an organic compound and is considered to be an endocrine disruptor, affecting exposed organisms, the environment, and human health. The performance of the microbial fuel cells (MFCs) was first controlled with specific operational conditions (pH, temperature, fuel feeding rate, and organic loading rate) to obtain the best accuracy of the sensor signal. After that, BPA concentrations varying from 50 to 1000 μg L-1 were examined under the biosensor's cell voltage generation. The outcome illustrates that MFC generates the most power under the best possible conditions of neutral pH, 300 mg L-1 of COD, R 1000 Ω, and ambient temperature. In general, adding BPA improved the biosensor's cell voltage generation. A slight linear trend between voltage output generation and BPA concentration was observed with R2 0.96, which indicated that BPA in this particular concentration range did not real harm to the MFC's electrogenic bacteria. Scanning electron microscope (SEM) images revealed a better cover biofilm after BPA injection on the surface electrode compared to it without BPA. These results confirmed that electroactive biofilm-based MFCs can serve to detect BPA found in wastewaters.

Ruggero Rossi, Bruce E Logan

Water research • 2022

Different microbial fuel cell (MFC) configurations have been successfully operated at pilot-scale levels (>100 L) to demonstrate electricity generation while accomplishing domestic or industrial wastewater treatment. Two cathode configurations have been primarily used based on either oxygen transfer by aeration of a liquid catholyte or direct oxygen transfer using air-cathodes. Analysis of several pilot-scale MFCs showed that air-cathode MFCs outperformed liquid catholyte reactors based on power density, producing 233% larger area-normalized power densities and 181% higher volumetric power densities. Reactors with higher electrode packing densities improved performance by enabling larger power production while minimizing the reactor footprint. Despite producing more power than the liquid catholyte MFCs, and reducing energy consumption for catholyte aeration, pilot MFCs based on air-cathode configuration failed to produce effluents with chemical oxygen demand (COD) levels low enough to meet typical threshold for discharge. Therefore, additional treatment would be required to further reduce the organic matter in the effluent to levels suitable for discharge. Scaling up MFCs must incorporate designs that can minimize electrode and solution resistances to maximize power and enable efficient wastewater treatment.

Dexter Hoi Long Leung, Yin Sze Lim, Kasimayan Uma et al.

Applied biochemistry and biotechnology • 2020

Microbial fuel cell (MFC) is a promising technology that utilizes exoelectrogens cultivated in the form of biofilm to generate power from various types of sources supplied. A metal-reducing pathway is utilized by these organisms to transfer electrons obtained from the metabolism of substrate from anaerobic respiration extracellularly. A widely established model organism that is capable of extracellular electron transfer (EET) is Shewanella oneidensis. This review highlights the strategies used in the transformation of S. oneidensis and the recent development of MFC in terms of intervention through genetic modifications. S. oneidensis was genetically engineered for several aims including the study on the underlying mechanisms of EET, and the enhancement of power generation and wastewater treating potential when used in an MFC. Through engineering S. oneidensis, genes responsible for EET are identified and strategies on enhancing the EET efficiency are studied. Overexpressing genes related to EET to enhance biofilm formation, mediator biosynthesis, and respiration appears as one of the common approaches.

Hong Liu, Bruce E. Logan

Environmental Science & Technology • 2004

Demonstration that removing the PEM in single-chamber MFCs can increase power generation.

Doaa Khodary Zater, Fatma I. Elzamik, Howaida M. Abdel Basit et al.

Sustainable Environment Research • 2024

Abstract This work evaluated the electrochemical, physical, biochemical, and molecular characterization of electrogens from a graphite felt anode when zinc oxide on activated carbon (ZnO/AC) was used as a cathodic electrocatalyst in a double-chambered microbial fuel cell (DCMFC). The electrochemical polarization behavior of the DCMFC showed that ZnO/AC had a higher power density (PD max ) of 89 mW m −2 with a corresponding cell current density (CD) of 248 mA m −2 and a voltage output of 395 mV, which was higher than those of the blank electrode used as a benchmark (PD max of 68 mW m −2 at a CD of 161 mA m −2 and a voltage of 421 mV). Furthermore, scanning electron microscopy and transmission electron microscopy revealed that the morphology and interior properties of the strains varied among the rods (bacilli), spirals (vibrios), and spheres (diplococci, staphylococci and streptococci). In addition, biochemical characterization via the Vitek2 compact system and molecular analysis via 16 S rRNA and 18 S rRNA gene sequencing revealed the occurrence of nine prevalent species that were correlated with Sphingobacterium spiritivorum, Ochrobactrum anthropicus, Pseudomonas mendocina, Stenotrophomonas maltophilia, Leuconostoc mesenteroides, Staphylococcus equorum, Bacillus subtilis HQ334981.1, Kocuria kristinae KC581674.1 and Saccharomyces cerevisiae NR111007.1. Consequently, the present study outlines different characterization strategies for electrogenic microbes that play an important role in the overall performance of DCMFC for scaling up and managing existing environmental pollution for sustainable energy generation.

Miroslav Hala, Roman Kodým, Martin Prokop et al.

ECS Meeting Abstracts • 2023

PEM fuel cells are a crucial link in the hydrogen economy because of their ability to transform the chemical energy of hydrogen into electrical energy with high efficiency at relatively low temperatures. Bipolar plates (BPs) are multifunctional components of PEM fuel cell stacks. Currently, material research in this field is focused on two promising material types: polymer carbon composites and metallic plates. Metallic plates have a number of advantages over composite materials, namely higher electrical conductivity, lower weight, and more effective manufacturing process. Typically, metallic BPs are manufactured with stamping or hydroforming. These methods are faster and cost-effective compared to machine milling or pressure extrusion typical for composite materials. Due to the nature of these processes, however, new channel geometries need to be considered. The first set of shape constrains comes from the forming properties of the material used. Other limitations result from the channel's ability to distribute the reagent gases, as well as to remove dissipate heat and water evolved. Traditional experimental testing methods involve an expensive and time-consuming production of samples and are unable to reliably determine local quantities. Within this study, mathematical modelling was used as a fast and cost-effective way of exploring the influence of the shape of the flow field channels on the distribution of local current density and species concentrations and performance of the PEM fuel cell. A full 3D model accounting for the reactants flow dynamics, multicomponent mass transport, electric charge flow, and electrode reaction kinetics was proposed and implemented. The Butler-Volmer equation was used to model the reaction kinetics. A simpler 1D model was developed to obtain the necessary kinetic parameters through fitting experimental data. Stefan-Maxwell equations were used to simulate the multicomponent mass transport on the cathode side of the cell. The data required were collected from the literature [1]. Darcy’s law was used to describe the transport of hydrogen in the porous structure of the anode. Through means of parametrical variation of geometrical parameters, such as the channel ground and rib width, angle of the channel walls, and the radius of the corners, we were able to compare numerous geometries in terms of the performance of the whole fuel cell. Also, the distribution of the species and local current densities was obtained. The width of the ribs and the ground of the channel were identified as the most influential parameters. In total, 18 combinations of channel ground and rib widths ranging from 0.1 to 4 mm and from 0.5 to 4 mm, respectively, were studied and compared to channels with square cross-section. In terms of the homogeneity of the local current densities, the narrowest combination offered the best results. This can be explained by the concentration of oxygen in the cathodic catalytic layer. In the case of wider channels, slow diffusion halted the transport of oxygen into the area of the catalytic layer at the closest distance from the channel ground, where the current was passing into the gas diffusion layer. This ultimately led to a large transport polarization and even fuel starvation in this area. Furthermore, in the well-supplied areas of the catalytic layer under the channels, where the bulk of gas transport is happening, local current densities were also low, because it is disadvantageous configuration for the electric charge flow. These two effects lead to a notably inhomogeneous local current density distribution with the most active area at the edge of the channel ground. In case of the narrow channels, it was possible to supply both reactants and charge into a larger area of the fuel cell, leading to much better utilization of the catalytical layer. From the obtained results, qualitative intervals of the ideal channel geometry were proposed. The results obtained contribute to the efficient development and faster commercialization of novel BPs. The CORE project Nr. TO01000306 benefits from Norway and Technology Agency of the Czech Republic Grant within the KAPPA Programme. [1] Bird, R. B.; Stewart, W. E.; Lightfoot, E. N. Transport Phenomena , 2nd ed.; John Wiley & Sons, Inc.: USA, 2006.

Tetsuya Nakamura, Kaito Mori, Shogo Fukushima et al.

ECS Meeting Abstracts • 2024

Boosting polymer electrolyte fuel cell (PEFC) performance is required in transportation. PEFC performance depends on the electrode reaction activity related to proton conductivity and oxygen diffusivity in catalyst layer (CL), consisting of Pt nanoparticles (Pt NPs), ionomer, water, and carbon supports. To achieve high proton conductivity and oxygen diffusivity, the optimization of CL structures such as Pt composition, ionomer/water distribution, and carbon support structures is essential by computational approaches, such as first-principles molecular dynamics (MD) and classical MD methods. The first-principles MD can describe chemical reactions, however can only simulate a small part of CL structures, consisting of a few hundred atoms. In contrast, classical MD can perform over 1 million atoms simulation to calculate whole CL structures, while the simple inter-atomic potential which enables 1 million atoms calculation, can not describe chemical reactions. Then, developing our original MD simulator "Laich", implementing MPI and OpenMP with ReaxFF inter-atomic potential, enabled us to calculate million atoms system reproducing whole CL structures and to simulate chemical reactions in whole CL structures. In this work, to design the higher-performance CL, we performed reactive MD simulations using a 1 million atoms CL model. A CL structure model was constructed with ionomers, water, Pt NPs, and carbon support. The carbon support composed of six meso pores with a size of 6 nm was constructed. To improve the hydrophilicity, hydroxyl groups and hydrogen terminated 32% and 31% of its surface carbon, respectively. Pt NPs were put on the carbon support at the exterior and in the interior of the meso pores. The Pt-supported carbon was coated with ionomers and water. Protons and oxygen were introduced into the system. Hereafter, we refer to this structure as a catalyst particle (CP) model (Fig. 1). To assess the influence of the carbon support structures on the electrode reactions, the oxygen diffusivity was evaluated from the trajectories of oxygen at the exterior and in the interior of the meso pores. Ideally, oxygen should be supplied to the Pt NPs without hindering its diffusion by obstacles. At the exterior of the meso pore, oxygen could not approach the Pt NPs, because ionomers and water were obstacles to the oxygen diffusion (Figs. 2(a)). Conversely, in the interior of the meso pores, oxygen could approach the Pt NPs via the gas phase since ionomers and water did not inhibit oxygen diffusion (Figs. 2(b)). From this analysis, the oxygen diffusivity showed higher value in the interior of the meso pores than at the exterior of the meso pores. Furtherly, it is reported that oxygen diffusivity in ionomers varies with temperature [1]. However, the influence of temperatures on oxygen diffusivity at the exterior and in the interior of the meso pores has not been analyzed. In this study, we calculated the mean squared displacement (MSD) and diffusion coefficients at 300 K and 365 K. At 300 K, oxygen diffusion coefficients (the linear regressions of MSD) at the exterior ( D exterior ) and in the interior of the meso pores ( D interior ) were 1.67×10 -10 m 2 /s and 3.02×10 -6 m 2 /s, respectively (Fig. 3(a)). At 365 K, D exterior and D interior were 12.3×10 -10 m 2 /s and 2.59×10 -6 m 2 /s, respectively (Fig. 3(b)). Therefore, D exterior and D interior respectively increased 7.37 and 0.86 times with increasing temperature. Next, to investigate whether the change of D exterior was caused only by temperatures, we calculated the oxygen diffusion coefficient at 1 atm ( D 1atm ) in an environment consisting of oxygen atoms only. As a result, D 1atm increased 1.05 times from 300 K to 365 K. By rising temperature, the increase of the oxygen diffusion coefficient showed 1.05 time at D 1atm , while it showed 7.37 time at D exterior . Therefore, other factors besides temperature affect the oxygen diffusivity. To identify the factors contributing to D exterior , we focused on the size of the water cluster, one of the obstacles to oxygen diffusion. Water clusters are defined as groups of water with an inter-molecular distance of less than 3.5 Å. The cluster size is defined as the number of water molecules forming the water cluster. Fig. 4 depicts the sizes of the 10 largest water clusters. As the temperature rose, the size of the largest water cluster decreased, while the size of other water clusters increased. These analyses indicate that the morphology of water clusters changed from continuous to discontinuous clusters with increasing temperature. Therefore, as water cluster sizes decrease by increasing temperature, oxygen diffuses through the gas phase. These results indicate that the control of the water cluster size improves the oxygen diffusivity. [1] K. Kudo et. al., Electrochim. Acta , 209 , 682-690 (2016). Figure 1

Miguel Mauricio Aguilera Flores, Verónica Avila Vázquez, Nahum Andrés Medellín Castillo

Frontiers in Sustainability • 2022

This work aimed to evaluate the devilfish bone char as an alternative material to be used as a bioanode in a microbial fuel cell (MFC) applied in bioenergy production from the pantoprazole biodegradation. The devilfish is an invasive species in Mexico and other countries, so its control and eradication are based on the integral use of its biomass. In addition, the bones are unusable waste and could be used as a raw material to manufacture the bioanode. Two MFCs with an anaerobic anode single chamber of 125 mL were operated independently using the fabricated bioanode and the carbon felt (conventional anode). Both MFCs were fed with 1 g/L of pantoprazole as substrate with a chemical oxygen demand (COD) of 210 ± 1.3 mg/L and 1.2 g of soil as inoculum. The two MFCs were characterized electrochemically, and the COD removal percentage was measured as an indicator of the pantoprazole biodegradation. The results showed that the MFC operated with the bioanode had a better performance than the conventional anode, since it reached a maximum power density of 1.22 mW/m 2 , being 156% higher than carbon felt. These values were consistent with the COD removal percentages reached in 10 days with values of 47.17 ± 0.23 and 43.34 ± 0.41%, respectively. Therefore, these findings provide a low-cost alternative carbonaceous material for the sustainable construction of MFC applied to produce bioenergy from the biodegradation of pharmaceutical products.

Ziqi Sun, Emiliana Fabbri, Lei Bi et al.

Journal of the American Ceramic Society • 2011

Although BaZr 0.8 Y 0.2 O 3−δ ( BZY ) possesses large bulk proton conductivity and excellent chemical stability, its poor sinterability and grain boundaries block proton conduction. In this work, the effect of Ca as a co‐dopant and as a sintering aid (as CaO ), on the sinterability, proton conductivity, and fuel cell performance of BZY was investigated. The addition of 4 mol% CaO significantly improved the BZY sinterability: BZY pellets with densities of 92.7% and 97.5% with respect to the theoretical density were obtained after sintering at 1500°C and 1600°C, respectively. The improved BZY sinterability by CaO addition resulted also in a large proton conductivity; at 600°C, the total conductivity of BZY– CaO was 2.14 × 10 −3 S/cm, in wet Ar . Anode‐supported fuel cells with 25 μm‐thick BZY– CaO electrolyte membranes were fabricated by a dual‐layer co‐firing technique. The peak power density of the fuel cell with a BZY– Ni /BZY–4 CaO /BZY–LSCF ( La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3−δ ) configuration was 141 mW/cm 2 at 700°C, several times larger than the reported values of BZY electrolyte membrane fuel cells sintered with the addition of CuO or ZnO , demonstrating promising features for practical fuel cell applications.

V. Bandlamudi, P. Bujlo, V. Linkov et al.

Fuel Cells • 2019

Abstract Degradation of phosphoric acid doped polybenzimidazole membrane based fuel cells under accelerated potential cycling conditions is investigated in current study. Three unit cells with identical high temperature membrane electrode assembly were assembled with three different cathode flow field designs. The fuel cell is cycled between 0.5 V and 0.9 V with 3 min dwelling time for each voltage set point. Performance degradation mechanisms associated with differences in cathode flow design are identified. The fuel cell with multiple serpentine design is operated for a maximum of 4,821 potential cycles with only 38.6% of initial performance remaining at the end‐of‐test (EoT), whereas straight and parallel design operated for only 3,188 cycles. The electrochemical characterization studies reveal the cause of observed performance losses from polarization curves. Irrespective of the design type used there are very high activation losses observed which accelerated with accelerated stress tests (AST) testing. The impedance studies reveal high charge transfer resistance related to increased platinum crystal growth on cathode and reduced electrochemical surface area (ECSA) of catalyst. Overall the AST results in irreversible performance loss and severe degradation of the cathode catalyst support and catalyst itself.

Ilias Apostolopoulos, Georgios Bampos, Amaia Soto Beobide et al.

Energies • 2021

The aim of the study was to assess the effect of anode materials, namely a carbon nanotube (CNT)-buckypaper and a commercial carbon paper (CP) on the performance of a two-chamber microbial electrolysis cell (MEC), in terms of hydrogen production and main electrochemical characteristics. The experiments were performed using both acetate-based synthetic wastewater and real wastewater, specifically the effluent of a dark fermentative hydrogenogenic reactor (fermentation effluent), using cheese whey (CW) as substrate. The results showed that CP led to higher hydrogen production efficiency and current density compared to the CNT-buckypaper anode, which was attributed to the better colonization of the CP electrode with electroactive microorganisms, due to the negative effects of CNT-based materials on the bacteria metabolism. By using the fermentation effluent as substrate, a two-stage process is developed, where dark fermentation (DF) of CW for hydrogen production occurs in the first step, while the DF effluent is used as substrate in the MEC, in the second step, to further increase hydrogen production. By coupling DF-MEC, a dual environmental benefit is provided, combining sustainable bioenergy generation together with wastewater treatment, a fact that is also reinforced by the toxicity data of the current study.

Zhe Lv, Xiaoying Huang, Xin Liu

ECS Transactions • 2021

In this work, button single cells with Ni-YSZ (anode support) | YSZ (electrolyte membrane) | Gd 0.1 Ce 0.9 O 1.95 (barrier layer) | La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (cathode) structure produced by mass-producing under industrial conditions were operated with dry hydrogen as fuel. In order to simulate single cell unit failure in series stack and local region failure of one cell, fuel gas depletion experiments were carried out in constant current and constant voltage discharge modes, respectively. During the discharging processes, the hydrogen fuel was fed and cut off alternatively for several times with different cut-off time, the output performances were measured to evaluate the stability and healthy of the single cell. The results show that the long time fuel depletion of the cell discharging in constant current mode can directly destroy the cell, it means a cell unit’s life in series stack can be affected when suffered fuel depletion. However, the cell discharging in constant voltage mode can keep stable status under fuel depletion condition, it means that the local fuel depletion in a certain cell will not destroy it.

Denver F. Cheddie, Norman D. H. Munroe

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

A parametric model of a proton exchange membrane fuel cell (PEMFC) operating with a polybenzimidazole (PBI) membrane is presented. The model is three dimensional and applicable for PEMFCs operating at intermediate temperatures (120–150 °C). It accounts for all transport and polarization phenomena, and the results compare well with published experimental data for equivalent operating conditions. Results for oxygen concentration and temperature variations are presented. The model predicts the oxygen depletion, which occurs in the catalyst area under the ribs, and which gives an indication of the catalyst utilization. Results also predict that for an output power density of 1 kW m−2, a cell temperature rise of up to 30 K can be expected for typical laboratory operating conditions. Parametric analyses indicate that significant gain in fuel cell performance can be expected by increasing the conductivity of the PBI membrane. Further, results demonstrate that when the catalyst region is well utilized, increasing the catalyst activity results in only a small improvement in performance.

Zhaodong Li, Chao Wu, Xiang Gao et al.

Research Square (Research Square) • 2020

Abstract Nature’s biocatalytic processes are driven by photosynthesis, whereby photosystems I and II are connected in series for light-stimulated generation of fuel products or electricity. Externally supplying electricity directly to the photosynthetic electron transfer chain (PETC) has numerous potential benefits, although strategies for achieving this goal have remained elusive. Here we report an integrated photo-electrochemical architecture which shuttles electrons directly to PETC in living cyanobacteria. The cathode of this architecture electrochemically interfaces with cyanobacterial cells lacking photosystem II activity that cannot perform photosynthesis independently. Illumination of the cathode channels electrons from external circuit to intracellular PETC through photosystem I, ultimately fueling CO2 conversion to acetate, a model fuel molecule with 9.32% energy efficiency, exceeding the efficiency of natural photosynthesis in higher plants (<1%) and cyanobacteria (~4-7%). The resulting “Electrophototrophic” bio-electrochemical hybrid has the potential to produce fuel chemicals with numerous advantages over standalone natural and artificial photosynthetic approaches.

Mehmet Suha Yazici, Tahsin Bahar

Asia-Pacific Journal of Chemical Engineering • 2021

Abstract Different cathode configurations with carbon paper (CP) and carbon cloth (CC) gas diffusion layer (GDL) are combined with Nafion® 115 for GOx enzyme fuel cells. Catalyst‐coated Nafion membrane (without a GDL) has resulted with highest impedance and lowest polarization response. Hot pressing of cathode gas diffusion electrode (GDE) onto the Nafion or physical placement onto the alternative chitosan membrane has reduced interface resistance 10 times compared with no‐GDL case. The best performance for the Nafion membrane is 2.1 mA cm −2 current density with hot‐pressed CC‐GDE. Smallest high‐frequency electrolyte (0.55 ohm) and charge transfer resistances (0.15 ohm) were measured with physically placed CC‐GDE on the alternative chitosan membrane resulting in maximum short current density of 3 mA cm −2 with a 4‐cm 2 single enzyme fuel cell.

Seung Woo Lee, Chae kyung Baik, Yong-Hun Cho et al.

ECS Meeting Abstracts • 2019

In the recent five years, the performance of alkaline membrane fuel cells (AMFCs) is greatly enhanced along with the development of alkaline electrolyte membrane and electrode technology including the ionomers and PtRu catalyst [1-3]. By replacing the Pt/C catalyst in the anode to PtRu/C catalyst, the performance of membrane electrode assembly (MEA) is improved significantly, which attributed to the lowering of hydrogen binding energy by PtRu alloy [3,4]. On the contrary, the adoption of non-platinum group metal (PGM) catalysts for hydrogen oxidation reaction (HOR) in the anode showed the very poor performance until now in the MEA level due to the very low HOR activity [1,5]. Thus, the further investigation of HOR catalysts with PGM having high activity and durability under alkaline condition is demanded. Among the PGM, recently, Ir and Ru have been received increasing attention as an alternative for the Pt catalyst for HOR because of their comparable exchange current density to that of Pt [1]. Recently, alloying of Ir and Ru provide the enhancement of HOR activity under alkaline condition in the half-cell evaluation [6,7]. In addition, Ir 1 Ru 1 nanowire supported on carbon catalyst displayed the higher performance as an anode catalyst than that of Pt/C catalyst in the MEA level [8]. In this study, the effect of metal loading of Ir 1 Ru 4 alloy supported on carbon support on the MEA performance is investigated. The metal loading of Ir 1 Ru 4 alloy is increased to 60 wt.% by repeating twice the impregnation and reduction processes for 30 wt.% loading, which applied to mitigate the enlargement of IrRu alloy nanoparticle when the metal loading increase from 30 wt.% to 60 wt.%. The MEA performance of 30 wt.% and 60 wt.% Ir 1 Ru 4 /C catalyst as a HOR catalyst is investigated by making the anode (0.4mg/cm 2 ) using a spray fabrication method. The current density at 0.6V is increased from the 0.6 to 0.93 A/cm 2 by increasing the metal loading in the supported Ir 1 Ru 4 alloy catalysts, which indicates the thickness of electrode is one factor for enhancing the MEA performance. In addition, the optimum ionomer to catalyst ratio is obtained as 0.3 for the 60 wt.% Ir 1 Ru 4 /C catalyst, which showed slightly better MEA performance than that of 40 wt.% Pt. This work was also supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (Grant NRF-2018M1A2A2063172 and NRF-2018M1A2A2063174). References E. S. Davydova, S. Mukerjee, F. Jaouen, and D. R. Dekel, ACS Catal. 8 , 6665 (2018) D. R. Dekel, J. Power Sources , 375 , 158 (2018). Y. Wang, G. Wang, G. Li, B. Huang, J. Pan, Q. Liu, J. Han, L. Xiao, J. Lu, and L. Zhuang, Energy Environ. Sci. , 8 , 177 (2015). W. Sheng, M. Myint, J. G. Chen and Y. Yan, Energy Environ. Sci., 6 , 1509 (2013). S. M. Alia and B. S. Pivovar, J. Electrochem. Soc. , 165 , F441 (2018). H. Wang and H. D. Abruna, J. Am. Chem. Soc. , 139 , 6807 (2017). J. Ohyama, D. Kumba abd A. Satsuma, J. Mater. Chem. A, 4 , 15980 (2016).

Jianuo Chen, Xuekun Lu, Lingtao Wang et al.

Nature Communications • 2024

Abstract High-temperature proton exchange membrane fuel cells (HT-PEMFCs) offer solutions to challenges intrinsic to low-temperature PEMFCs, such as complex water management, fuel inflexibility, and thermal integration. However, they are hindered by phosphoric acid (PA) leaching and catalyst migration, which destabilize the critical three-phase interface within the membrane electrode assembly (MEA). This study presents an innovative approach to enhance HT-PEMFC performance through membrane modification using picosecond laser scribing, which optimises the three-phase interface by forming a graphene-like structure that mitigates PA leaching. Our results demonstrate that laser-induced modification of PA-doped membranes, particularly on the cathode side, significantly enhances the performance and durability of HT-PEMFCs, achieving a peak power density of 817.2 mW cm⁻² after accelerated stress testing, representing a notable 58.2% increase compared to untreated membranes. Furthermore, a comprehensive three-dimensional multi-physics model, based on X-ray micro-computed tomography data, was employed to visualise and quantify the impact of this laser treatment on the dynamic electrochemical processes within the MEA. Hence, this work provides both a scalable methodology to stabilise an important future membrane technology, and a clear mechanistic understanding of how this targeted laser modification acts to optimise the three-phase interface of HT-PEMFCs, which can have impact across a wide array of applications.

K Scott, I Cotlarciuc, I Head et al.

Journal of Chemical Technology & Biotechnology • 2008

Abstract BACKGROUND: Marine sediment microbial fuel cells (MFC) utilise oxidisable carbon compounds and other components present in sediments on ocean floors and similar environments to produce power in conjunction with, principally, oxygen reduction at the cathode in the overlying water. The aim of the work was to investigate a range of cathode materials for sediment MFC, to achieve relatively high levels of power. RESULTS: Cell potential and power density performance data are reported for sediment MFC using cathodes of: carbon sponge, cloth and paper, graphite and reticulated vitreous carbon (RVC), Co and Fe‐Co tetramethoxyphenyl porphyrin (FeCoTMPP) and platinised carbon and titanium. The anode was graphite cloth. After a period of stabilisation, open circuit voltages of 700 mV and maximum power densities of 62 mW m −2 were obtained, using FeCoTMPP. Relatively low cost carbon cathodes gave power densities of around 30 mW m −2 . CONCLUSIONS: The study has shown that low level power can be produced from marine sediments using MFC without separators between the fuel and seawater containing dissolved oxygen. Cathode performance was an important factor determining the power output. Electrocatalyst at the cathode improved performance: FeCoTMMP gave power densities of 60 mW m −2 which was twice that achieved with the best un‐modified carbon. Copyright © 2008 Society of Chemical Industry

Xinhai Xu, Shuyang Zhang, Peiwen Li

ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology • 2014

Catalytic autothermal reforming (ATR) is one promising technology to effectively produce hydrogen and syngas from heavy hydrocarbon fuels for fuel cell applications. The present study describes the development of a cylindrical 1.5 kWe scale autothermal reformer for on-board SOFCs. NiO-Rh bimetallic catalysts supported on 400 cpsi cordierite monoliths were experimentally examined in the reformer. Promoters including cerium, potassium and lanthanum were introduced in the catalysts preparation to improve their performance. Dodecane (C12H26) was used as a surrogate for desulfurized commercial Jet-A fuel (C11.6H22.3) to study the hydrogen selectivity and efficiency of ATR reactions with different catalysts. Gas chromatography (GC) equipped with TCD detector was used to monitor the concentration of H2, CO, CO2 and N2 in the reformate. The catalysts screening tests were performed at the same operation conditions including inlet temperatures, reactor temperature, steam to carbon ratio and oxygen to carbon ratio. The best catalyst was reported to have efficiency about 85 percent. The optimized reactor operation temperature was reported as 700 °C.

Carlos Munoz‐Cupa, Amarjeet Bassi

Environmental Progress & Sustainable Energy • 2023

Abstract Heavy metal removal and simultaneous energy production were studied using a dual chambered Microbial Fuel Cell inoculated with Shewanella oneidensis MR‐1 in the anode. Synthetic wastewater was prepared with Cu (II), Mg (II), Mn (II), Zn (II), Na, and Phenol based on desalter effluent from refinery processes at different metal concentrations. In this study, a maximum open‐circuit voltage of 517.6 mV was reached at Conc. 5 with wastewater in the anode chamber, and 127.7 mV at Conc. 3 was produced with synthetic wastewater in the cathode chamber. Moreover, μ at Conc. 5 was 0.1133 h −1 , demonstrating bacterial growth under metal and phenol concentrations. The highest metal removal in the anode for Cu (II), Mg (II), Mn (II), Zn (II), and Na was 93%, 85%, 93%, 88%, and 36%, respectively. In the cathode chamber the removal of Cu (II), Mg (II), Mn (II), Zn (II), and Na was 98%, 49%, 57%, 59%, and 36%, respectively. During the operation in the anode, SEM images showed that the bacterial nanowires are formed in response to toxic and anaerobic environments which contribute to the bacterial growth. These nanowires increased the metal removal and the voltage production as a consequence of a higher electron rate from the anode to the cathode due to the higher extracellular membrane surface area. S. oneidensis is a bacterium with metal‐reducing characteristics, and it is suitable for metal removal and electron transport from carbon sources, demonstrated in voltage production with microbial fuel cells.

Li-Chun Wu, Guey-Horng Wang, Teh-Hua Tsai et al.

Sensors • 2019

Chromium (VI) [Cr(VI)] compounds display high toxic, mutagenic, and carcinogenic potential. Biological analysis techniques (e.g., such as enzyme-based or cell-based sensors) have been developed to measure Cr(VI); however, these biological elements are sensitive to the environment, limited to measuring trace Cr(VI), and require deployment offsite. In this study, a three-stage single-chambered microbial fuel cell (SCMFC) biosensor inoculated with Exiguobacterium aestuarii YC211 was developed for in situ, real-time, and continuous Cr(VI) measurement. A negative linear relationship was observed between the Cr(VI) concentration (5–30 mg/L) and the voltage output using an SCMFC at 2-min liquid retention time. The theoretical Cr(VI) measurement range of the system could be extended to 5–90 mg/L by connecting three separate SCMFCs in series. The three-stage SCMFC biosensor could accurately measure Cr(VI) concentrations in actual tannery wastewater with low deviations (<7%). After treating the wastewater with the SCMFC, the original inoculated E. aestuarii remained dominant (>92.5%), according to the next-generation sequencing analysis. The stable bacterial community present in the SCMFC favored the reliable performance of the SCMFC biosensor. Thus, the three-stage SCMFC biosensor has potential as an early warning device with wide dynamic range for in situ, real-time, and continuous Cr(VI) measurement of tannery wastewater.

Nour-eddine Lazar, Driss Mazkad, Hamza Kharti et al.

Materials for Renewable and Sustainable Energy • 2024

Abstract Microbial fuel cells (MFCs) have attracted a great deal of attention as a promising technology for recovering electricity from organic substances by harnessing the metabolic activities of microorganisms. The objective of this study is to assess the efficacy of a LiTa 0.5 Nb 0.5 O 3 /g-C 3 N 4 (LTN/g-C 3 N 4 ) heterojunction as a photocathode catalyst within a single-chamber microbial fuel cell operating under both light irradiation and dark conditions. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive X-Ray spectroscopy (EDS) were used to conduct a comprehensive analysis of the composite catalyst, revealing its exceptional purity and unique properties. After 120 h of exposure to visible light, the maximal power density of the MFC containing LTN/g-C3N4-modified carbon cloth was determined to be 667.7 mW/m 3 . The power density achieved with the presence of light was approximately three times greater than the power density obtained without light in the MFC (235.64 mW/m 3 ). In addition, the study determined that the removal efficiencies of chemical oxygen demand (COD) were 88.4% and 66.5% when exposed to light and in the absence of light, respectively. These findings highlight the potential of the non-precious LTN/g-C 3 N 4 photocatalyst as a viable alternative for effective wastewater treatment and power generation in microbial fuel cells with a single chamber configuration.

Farzad Ahmadi, Ramin Roshandel

Journal of Fuel Cell Science and Technology • 2013

Performance of polymer electrolyte membrane fuel cells (PEMFC) at high current densities is limited to transport reactants and products. Furthermore, large amounts of water are generated and may be condensed due to the low temperature of the PEMFC. Development of a two-phase flow model is necessary in order to predict water flooding and its effects on the PEMFC performance. In this paper, a multiphase mixture model (M2) is used, accurately, to model two-phase transport in porous media of a PEMFC. The cathode side, which includes channel, gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL), is considered as the computational domain. A multidomain approach has been used and transport equations are solved in each domain independently with appropriate boundary conditions between GDL and MPL. Distributions of species concentration, temperature, and velocity field are obtained, and the effects of MPL on species distribution and fuel cell performance are investigated. MPL causes a saturation jump and a discontinuity in oxygen concentration at the GDL/MPL interface. The effect of MPL thickness on fuel cell performance is also studied. The results revealed that the MPL can highly increase the maximum power of a PEMFC.

Nie Luo, George H. Miley, Joe Mather et al.

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

A kilo-Watt-class direct sodium-borohydride/hydrogen-peroxide (NaBH4/H2O2) fuel cell is fabricated and characterized in this research. Aqueous solution of NaBH4 is directly utilized at the fuel cell anode in place of gaseous hydrogen. Similarly H2O2/water solution is directly reduced at the cathode without being first converted through molecular oxygen. The direct utilization of fuel/oxidant results in much higher (35% higher) efficiency in energy utilization. The potential for a very high efficiency (over 80%) was fully validated in the experiments, because the use of H2O2 overcomes the oxygen over-potential problem inherent to prior H2/O2 fuel cell designs. Initial results indicate: 1) conversion efficiency over 50% at a practical current density of 200 mA/cm2; 2) power density over 0.5 W/cm2, at 60 degree Celsius. The kilo-Watt-stack consists of 24 cells, generating an OCV (open circuit voltage) of ∼ 42 V. The design of the reactant manifold overcomes some issues unique to an all-liquid-reactant fuel cell. Such a technology is ideal for propulsion/power in air independent environment such as space and underwater.

Karren L. More, David A. Cullen, Brian Sneed et al.

ECS Meeting Abstracts • 2016

Polymer electrolyte membrane (PEM) fuel cell performance and materials degradation, particularly associated with the cathode catalyst layer (CCL), can be directly attributed to the structure and chemistry of individual material components, as well as their uniformity/homogeneity within a CCL. The individual material constituents used to form the CCL within the membrane electrode assemblies (MEAs), which include the electrocatalyst, catalyst support, and ionomer films, and especially the critical interfaces that are formed between these various constituents, are critically importance in controlling fuel cell perfomance. Understanding the specific microstructural characteristics of the individual materials within the CCL, and how the materials interact to “form” the CCL, is important for identifying materials optimization parameters that can significantly enhance performance and durability. Materials in several states/conditions, e.g., prior to incorporation in the CCL (as-synthesized), after MEA preparation (CCL), and after fuel cell testing, are beig evaluated and quantified using a combination of advanced electron microscopy methods, which are used to interrogate the materials constituents and interfacial structures and chemistries from the μm- to the Å-level. The as-processed (prior to and following incorporation into a CCL) microstructural evidence is directly correlated with observations of materials-specific degradation mechanisms that contribute to fuel cell performance loss, and are then used to identify potential processing variables (materials-based mitigation strategies) to improve the microstructure and compositional homogeneity within the electrode structure, and enhance MEA durability and stability during fuel cell operation. Research efforts at Oak Ridge National Laboratory are focused on the high-resolution microstructural and microchemical characterization of MEAs fabricated using different electocatalysts (typically Pt-based) and catalyst loadings, carbon-based support materials, and ionomer solutions, as well as the same MEAs subjected to accelerated stress tests (ASTs) designed to degrade specific MEA components. While a significant microscopy effort has been aimed towards understanding catalyst degradation (e.g., coarsening, de-alloying), recently, high-resolution analytical microscopy methods have been used to directly image/map the distribution and chemistry of the ionomer films/layers within CCLs, results of which are being combined with high-resolution imaging and 3-D tomography data of powder materials and MEAs, to provide unprecedented insight into the MEA architecture and interfaces (ionomer/support, ionomer/catalyst, catalyst/support, ionomer/pore). This presentation will focus on understanding materials distributions within CCLs as a function of materials used and ink/MEA processing variables, e.g., initial ionomer and/or ink chemistry, electrocatalyst (type, content, and dispersion), and the type of carbon support used. Additionally, the stability of the ionomer films, electrocatalysts, and support structures in CCLs following ASTs designed specifically for either catalyst degradation or carbon corrosion, will be evaluated. ________________________________________________________________________ Research sponsored by (1) the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy and (2) Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility.

Bahareh Alsadat Tavakoli Mehrabadi, Jonathan Braaten, Gang Wu et al.

ECS Meeting Abstracts • 2020

One of the effective ways to reduce the cost of polymer electrolyte membrane fuel cells (PEMFCs) is to reduce the amount of platinum-group metal (PGM) catalysts used for the oxygen reduction reaction (ORR). Recently, highly active platinum group metal-free (PGM-free) catalysts were developed and applied for the ORR reaction [1-3]. Significant developments have been made on the chemistry of PGM-free catalysts and their kinetic performance [4-6]. However, despite all the progress, some challenges remain before they are commercially viable. Mass-transport within the very thick catalyst layer (CL) displays a key challenge for further improvement of the fuel cell performance of PGM-free catalysts. Understanding of the structure of CL including the distribution of active sites and the ionomer inside the CL play an important role in the development of stable PGM-free cathodes capable of high power density. In the present work, our objective has been to demonstrate the effects of the ionomer content, solvents, and equivalent weight (EW) on electrode performance. The structure of the ionomer (i.e., short-side-chain vs long-side chain ionomer) as well as the effect of the relative humidity (RH) have been considered. To increase the proton conductivity of the cathode and improve the catalysts’ effectiveness across its thickness, it is important to optimize the ionomer type and its EW. In this work, we used the nanoscale X-ray computed tomography (nano-CT) method to characterize the morphology and transport properties of PGM-free cathodes. Our results show the sensitivity of the cathode’s performance to the hydrophilicity of the ionomer films. We found that electrodes with a lower ionomer EW have a tendency to retain more water than electrodes with a higher EW. Thus, at high current density conditions where significant water is being generated, the lower EW ionomers showed reduced performances due to electrode flooding when using the same processing and ionomer loading. In general, higher MEA performance at 100% RH was achieved using more hydrophobic ionomers (higher EW) with a greater proportion of hydrophobic fluoropolymer backbone or by using ink formulations that enhanced the hydrophobicity of a particular ionomer. Acknowledgment This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office (FCTO) under Award Number DE-EE0008076. References 1. F. Jaouen, E. Proietti, M. Lefevre, R. Chenitz, J. Dodelet, G. Wu, H. Chung, C. Johnston, P. Zelenay, Energ. Environ. Sci. 4, 114-130 (2011). 2. G. Wu, K.L. More, C.M. Johnston and P. Zelenay, Science. 332, 443-447 (2011). 3. J. Suntivich, K.J. May, H.A. Gasteiger, J.B. Goodenough and Y. Shao-Horn. Science. 334, 1383-1385 (2011). 4. G. Wu and P. Zelenay, Acc. Chem. Res. 46, 1878-1889 (2013). 5. E. Proietti, F. Jaouen, M. Lefèvre, N. Larouche, J. Tian, J. Herranz and J.-P. Dodelet, Nat. Commun. 2, 416 (2011). 6. X. Wang, H. Zhang, H. Lin, S. Gupta, C. Wang, Z. Tao, H. Fu, T. Wang, J. Zheng, G. Wu and X. Li, Nano Energy. 25, 110-119 (2016).

Natalia Macauley, Magali Spinetta, Sichen Zhong et al.

ECS Meeting Abstracts • 2020

In a proton exchange membrane (PEM) fuel cell, the local oxygen transport across the ionomer film in the catalyst layer has a significant impact on electrode performance especially at high current density. 1 It is therefore crucial to use ionomers that have higher oxygen permeability than the baseline Nafion. In this work, novel ionomers with increased oxygen permeability have been synthesized by copolymerization of perfluoro-2,2-dimethyl-1,3-dioxole (PDD) with perfluoro(4-methyl-3,6-dioxaoct-7-ene) sulfonyl fluoride (PFSVE) and a ter-monomer. PDD is the main source of higher permeability due to its bulky structure, PFSVE provides ionic conductivity and the amount of the ter-monomer is adjusted to achieve high yields without compromising the equivalent weight (EW). The ring structure of PDD creates additional open space within the ionomer structure for improved gas permeability. Some of the newly developed ionomers have up to five times higher permeability than Nafion, which should result in a significant improvement of fuel cell performance, mainly at high current densities. Ionomers with different PDD content and equivalent weight have been studied to establish the correlation between ionomer properties and MEA performance. Local oxygen resistance, ionomer sheet resistance, ionomer coverage, and SO 3 - group coverage will be evaluated and correlated to electrode performance. The performance and durability of the electrodes using high permeability ionomer will be correlated to the ionomer interaction with catalyst particle. This work will provide a comprehensive understanding of interactions among Pt, carbon, ionomer and their impact on the electrode structure and fuel cell performance and durability. The attained information will be used to improve fuel cell electrode design. Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-SC0018597. References: 1. Baker et al, J. Electrochem. Soc. 156, B991 (2014).