E. K. Gebeyehu, X. Sui, Biruk Fentahun Adamu et al.

Gels • 2022

The use of hydrogel in tissue engineering is not entirely new. In the last six decades, researchers have used hydrogel to develop artificial organs and tissue for the diagnosis of real-life problems and research purposes. Trial and error dominated the first forty years of tissue generation. Nowadays, biomaterials research is constantly progressing in the direction of new materials with expanded capabilities to better meet the current needs. Knowing the biological phenomenon at the interaction among materials and the human body has promoted the development of smart bio-inert and bio-active polymeric materials or devices as a result of vigorous and consistent research. Hydrogels can be tailored to contain properties such as softness, porosity, adequate strength, biodegradability, and a suitable surface for adhesion; they are ideal for use as a scaffold to provide support for cellular attachment and control tissue shapes. Perhaps electrical conductivity in hydrogel polymers promotes the interaction of electrical signals among artificial neurons and simulates the physiological microenvironment of electro-active tissues. This paper presents a review of the current state-of-the-art related to the complete process of conductive hydrogel manufacturing for tissue engineering from cellulosic materials. The essential properties required by hydrogel for electro-active-tissue regeneration are explored after a short overview of hydrogel classification and manufacturing methods. To prepare hydrogel from cellulose, the base material, cellulose, is first synthesized from plant fibers or generated from bacteria, fungi, or animals. The natural chemistry of cellulose and its derivatives in the fabrication of hydrogels is briefly discussed. Thereafter, the current scenario and latest developments of cellulose-based conductive hydrogels for tissue engineering are reviewed with an illustration from the literature. Finally, the pro and cons of conductive hydrogels for tissue engineering are indicated.

Andrew W. Tricker, Tugrul Y. Ertugrul, J. K. Lee et al.

Advanced Energy Materials • 2023

Green hydrogen, produced via water electrolysis using renewable electricity, will play a crucial role in decarbonizing industrial and heavy‐duty transportation sectors. Anion exchange membrane water electrolyzers (AEMWEs) can overcome many of the performance and cost limitations of incumbent technologies, however, still suffer from durability challenges due to oxidative instability of anion‐exchange ionomers. Herein, the use of an electro‐active porous transport layer as anode (PTL‐electrode) is demonstrated to enable efficient and durable AEMWEs. The stainless‐steel PTL‐electrodes are shown to have superior performance and durability compared to traditional catalyst layers containing ionomer and nanoparticle catalysts. An AEMWE cell operating at 2 A cm−2 for over 600 h exhibited a degradation rate of just 5 µV h−1. During operation, the surface composition of the stainless steel transforms into a mixture of iron and nickel oxyhydroxides, contributing to enhanced oxygen‐evolution reaction activity. The combination of experimental work and modeling elucidates how the bulk structure of the PTL‐electrode offers an additional design dimension to further improve electrolyzer performance. Lastly, a surface modification strategy is applied to a PTL‐electrode to achieve an even higher performing AEMWE (2.3 vs 2.0 A cm−2 at 1.8 V). Overall, this work lays out pathways toward more efficient, durable, and affordable AEMWEs.

Eric de Souza Gil, Emily Moreno, Luane Ferreira Garcia et al.

KnE Engineering • 2020

Electrochemical remediation is an innovative technique that utilizes electro-oxidation reactions to degrade micropollutants such as doxorubicin (DOX) that is a drug widely used to treat many types of cancer, and it is present in hospital effluents. The aim of this work is to evaluate the efficiency of active and non-active electrodes in DOX degradation during electrochemical treatments. AuO-TiO2@graphite, a nanostructured electrode, and BDD, a commercial electrode, were used as active and non-active electrodes respectively. DOX treatments were realized at concentration of 1.25 mmol L-1 in medium with 10 mmol L-1 NaCl as support electrolyte. Studies were realized in 5 V of voltage source. Results: The treatment of DOX with BDD promoted 100% of DOX degradation in 20 min, while the same result was obtained for the AuO-TiO2@graphite in 40 min of treatment. Also, the modified electrode presented an energy expenditure of 1.12 kWh m-3 and the BDD achieved 0.462 kWh m-3. Thus, the active and non-active electrodes were efficient to promote DOX degradation, and the BDD, the non-active electrode demonstrated a better performance. Keywords: Eletro-Oxidadion, Modified Graphite Anodes, BDD, Doxorubicin, Micropollutants

Ambroise Wattez, Rick van Kessel

Offshore Technology Conference • 2016

The first generations of wave energy converters have had a number of forms, but all are essentially large steel structures concentrating the power take off onto small mechanical devices. A number of prototype devices have been installed offshore, but due to their high fabrication and installation costs, coupled with significant maintenance requirements, the production of electricity at an acceptable cost has remained elusive. To avoid the limitations of these devices, a second generation wave energy converter is being developed using electro active polymers (EAP), which are capable of generating electricity directly from wave action without the need for any mechanical power take off. The resulting system is flexible and possesses an infinite number of degrees of freedom, allowing wave energy to be captured more efficiently than with conventional devices. Deployed offshore, such a device would have no complex mechanical parts, would function silently, and would require minimal maintenance. The economics of such a system lead to predictions of a cost of electricity significantly below the levels of the first generation devices. The paper explains the principals involved in using EAP for the generation of electricity, the application of EAP to wave energy conversion, and reports key results from the ongoing development program. The paper also describes the main features of the prototype wave energy converter system presently under development for deployment offshore.

Anas Kanan, Michael Kaliske

PAMM • 2021

Abstract Electro‐active polymers (EAP) are smart materials that can deform dramatically and quasi‐instantaneously in response to an applied electric field. These properties make them suitable to be used as soft robotic actuators. As any passive rubber‐like material, those electro‐sensitive components are quasi‐incompressible and may show pronounced time‐dependent hysteresis behaviour. The direction of the electric field induced deformation can be tuned by incorporating stiff fibres in a relatively soft EAP, which renders an anisotropic mechanical response of the whole composite. The contribution at hand presents a constitutive model which is suitable for the simulation of an electro‐viscoelastic behaviour of transversely isotropic EAP. The material model is based on an additive split of the total energy function into purely mechanical, electrical and coupled electro‐mechanical contributions. The mechanical part of the energy is further decomposed into isotropic and anisotropic parts. For the electrical and the coupled contributions, formulations for both the perfectly linear dielectric and the nonlinear (deformation dependent) electrical response are presented. Regarding the numerical implementation, a mixed quasi‐incompressible and quasi‐inextensible electro‐mechanical finite element is developed. In addition to the displacement and electric potential, four additional field variables are introduced. The capabilities of the proposed theory and its numerical treatment are demonstrated through simulations of several electro‐mechanical actuator structures. The utilization of a quasi‐inextensible finite element is shown to improve the convergence behaviour of the numerical solution, allowing for the simulation of complex loading scenarios of fibre reinforced EAP in an efficient manner.

J. Bial, C. A. Trepmann

• 2013

Abstract. We examine the microfabric development in high-pressure, low-temperature metamorphic serpentinite mylonites exposed in the Erro-Tobbio Unit (Voltri Massif, Italy) using polarization microscopy and electron microscopy (SEM/EBSD, EMP). The mylonites are derived from mantle peridotites, were serpentinized at the ocean floor and underwent high pressure metamorphism during Alpine subduction. They contain diopside and olivine porphyroclasts embedded in a fine-grained matrix essentially consisting of antigorite. The porphyroclasts record brittle and crystal-plastic deformation of the original peridotites in the upper mantle at stresses of a few hundred MPa. After the peridotites became serpentinized, deformation occurred mainly by dissolution-precipitation creep resulting in a foliation with flattened olivine grains at phase boundaries with antigorite, crenulation cleavages and olivine and antigorite aggregates in strain shadows next to porphyroclasts. It is suggested that the fluid was provided by dehydration reactions of antigorite forming olivine and enstatite during subduction and prograde metamorphism. At sites of stress concentration around porphyroclasts antigorite reveals an associated SPO and CPO, characteristically varying grain sizes and sutured grain boundaries, indicating deformation by dislocation creep. Stresses were probably below a few tens of MPa in the serpentinites, which was not sufficiently high to allow for crystal-plastic deformation of olivine at conditions at which antigorite is stable. Accordingly, any intragranular deformation features of the newly precipitated olivine in strain shadows are absent. The porphyroclast microstructures are not associated with the microstructures of the mylonitic matrix, but are inherited from an independent earlier deformation. The porphyroclasts record a high-stress deformation in the upper mantle of the oceanic lithosphere probably related to rifting processes, whereas the antigorite matrix records deformation at low stresses during subduction and exhumation.

Simone Di Plinio, Sjoerd J. H. Ebisch

Human Brain Mapping • 2018

Abstract Neuroimaging research made rapid advances in the study of the functional architecture of the brain during the past decade. Many proposals endorsed the relevance of large‐scale brain networks, defined as ensembles of brain regions that exhibit highly correlated signal fluctuations. However, analysis methods need further elaboration to define the functional and anatomical extent of specialized subsystems within classical networks with a high reliability. We present a novel approach to characterize and examine the functional proprieties of brain networks. This approach, labeled as brain network profiling (BNP), considers similarities in task‐evoked activity and resting‐state functional connectivity across biologically relevant brain subregions. To combine task‐driven activity and functional connectivity features, principal components were extracted separately for task‐related beta values and resting‐state functional connectivity z ‐values (data available from the Human Connectome Project), from 360 brain parcels. Multiple clustering procedures were employed to assess if different clustering methods (Gaussian mixtures; k ‐means) and/or data structures (task and rest data; only rest data) led to improvements in the replication of the brain architecture. The results indicated that combining information from resting‐state functional connectivity and task‐evoked activity and using Gaussian mixtures models for clustering produces more reliable results (99% replication across data sets). Moreover, the findings revealed a high‐resolution partition of the cerebral cortex in 16 networks with unique functional connectivity and/or task‐evoked activity profiles. BNP potentially offers new approaches to advance the investigation of the brain functional architecture.

Allene Jeanes

Journal of Polymer Science: Polymer Symposia • 1974

Abstract Hydrophilic macromolecular polysaccharides, selected for their distinctive constitution and unusual properties, are produced industrially from common sugars by nonpathogenic microorganisms. The α‐(1–6)‐linked D‐glucan dextran and fractions of defined lower molecular‐weight produced from it are derivatized chemically to a variety of ionogenic substances for uses such as: anticoagulant, antilipemic, and peptic‐ulcer alleviating agents; to enhance the sensitivity and covering power of x‐ray and photographic emulsions; and separations of sensitive biochemical products by two‐phase liquid distribution and ion‐exchange and affinity chromatography. The polyanionic heteropoly‐saccharide xanthan is used in many industries (such as agriculture, abrasives, ceramics, food, paint, petroleum production, and textile) for its thickening and suspending ability even in the presence of high salt concentrations, reversible shear thinning, synergistic interaction with galactomannans, and excellent stability to heat and to acidic and basic conditions. Other water‐soluble polysaccharide‐polyelectrolytes, produced in liquid cultures unattached to the microbial cells, have potentially useful properties.

Mike Dimpfl

cultural geographies • 2018

At a major research institution in the American South, cleanliness norms are intensifying for students, housekeepers, and institutional administrators. Whether individual practice, waged labor, or institutional policy concern, daily hygiene routines often refer to invisible or otherwise absent threats to health. Broadly construed as ‘germs’, these include flu, norovirus, and Escherichia coli, as well as dirt, dust mites, allergens, and mold. Their mobilization influences students’ and housekeepers’ interpersonal relations in a range of common university spaces, revealing connections among disease, embodiment, risk, and care. At the same time, concern with germs aligns with institutional efforts to control a historically powerful cadre of workers. Connections between students’ experiences of health and disease risk and housekeeper and institutional orientation to those risks are obscure, although fundamentally constitutive of each other. Analysis of their different, but intersecting ideas about microbial hygienic risk draws together critical geographies of social reproductive labor, cultural geographies of more-than-human agency, and a recent call to elaborate a political ecology of health. Ethnographic and archival data reveal how germs retrench institutional disparities, placing the (re)production of student cleanliness practices and the working lives of housekeepers in tension. For students, germs help shore up valorized subject positions, informing regimes of self-care. For department administrators, a new employee management regime made the potential of microbial threats to student health a scientific instrument of labor control. For housekeepers, germs are particularly evocative of the demand to care for student health by managing exposure to microbial disease risk. Exploring different mobilizations of germs reveals the importance of more-than-human life to systems of and divisions between social reproductive labor regimes on campus.

H. Wu, X. Lou

Science Advances • 2017

Metal-organic frameworks and their derived materials are highly interesting for electrochemical energy storage and conversion. In addition to their conventional uses, metal-organic frameworks (MOFs) have recently emerged as an interesting class of functional materials and precursors of inorganic materials for electrochemical energy storage and conversion technologies. This class of MOF-related materials can be broadly categorized into two groups: pristine MOF-based materials and MOF-derived functional materials. Although the diversity in composition and structure leads to diverse and tunable functionalities of MOF-based materials, it appears that much more effort in this emerging field is devoted to synthesizing MOF-derived materials for electrochemical applications. This is in view of two main drawbacks of MOF-based materials: the low conductivity nature and the stability issue. On the contrary, MOF-derived synthesis strategies have substantial advantages in controlling the composition and structure of MOF-derived materials. From this perspective, we review some emerging applications of both groups of MOF-related materials as electrode materials for rechargeable batteries and electrochemical capacitors, efficient electrocatalysts, and even electrolytes for electrochemical devices. By highlighting the advantages and challenges of each class of materials for different applications, we hope to shed some light on the future development of this highly exciting area.

Q. Ding, Chen Li, Haijun Wang et al.

Chemical Communications • 2021

Heavy metal ions are one of the main sources of water pollution. Most heavy metal ions are carcinogens that pose a threat to both ecological balance and human health. With the increasing demand for heavy metal detection, electrochemical detection is favorable due to its high sensitivity and efficiency. Here, after discussing the pollution sources and toxicities of Hg(ii), Cd(ii), As(iii), Pb(ii), UO2(ii), Tl(i), Cr(vi), Ag(i), and Cu(ii), we review a variety of recent electrochemical methods for detecting heavy metal ions. Compared with traditional methods, electrochemical methods are portable, fast, and cost-effective, and they can be adapted to various on-site inspection sites. Our review shows that the electrochemical detection of heavy metal ions is a very promising strategy that has attracted widespread attention and can be applied in agriculture, life science, clinical diagnosis, and analysis.

C. Martínez-Huitle, M. Rodrigo, I. Sirés et al.

Chemical Reviews • 2015

Traditional physicochemical and biological techniques, as well as advanced oxidation processes (AOPs), are often inadequate, ineffective, or expensive for industrial water reclamation. Within this context, the electrochemical technologies have found a niche where they can become dominant in the near future, especially for the abatement of biorefractory substances. In this critical review, some of the most promising electrochemical tools for the treatment of wastewater contaminated by organic pollutants are discussed in detail with the following goals: (1) to present the fundamental aspects of the selected processes; (2) to discuss the effect of both the main operating parameters and the reactor design on their performance; (3) to critically evaluate their advantages and disadvantages; and (4) to forecast the prospect of their utilization on an applicable scale by identifying the key points to be further investigated. The review is focused on the direct electrochemical oxidation, the indirect electrochemical oxidation mediated by electrogenerated active chlorine, and the coupling between anodic and cathodic processes. The last part of the review is devoted to the critical assessment of the reactors that can be used to put these technologies into practice.

Shenzhen Xu, E. Carter

Chemical Reviews • 2018

Electrochemical and photoelectrochemical CO2 reduction technologies offer the promise of zero-carbon-emission renewable fuels needed for heavy-duty transportation. However, the inert nature of the CO2 molecule poses a fundamental challenge that must be overcome before efficient (photo)electrochemical CO2 reduction at scale will be achieved. Optimal catalysts exhibit enduring stability, fast kinetics, high selectivity, and low manufacturing cost. Identifying catalytic mechanisms of CO2 reduction in (photo)electrochemical systems could accelerate design of efficient catalysts. In recent decades, numerous theoretical studies have contributed to our understanding of CO2 reduction pathways and identifying rate-limiting steps. Although a significant body of work exists regarding homogeneous electrocatalysis for CO2 reduction, this review focuses specifically on the theory of heterogeneous (photo)electrochemical reduction. We first give an overview of the relevant thermodynamics and semiconductor physics. We then introduce important, widely used theoretical techniques and modeling approaches to catalysis. Recent progress in elucidating mechanisms of heterogeneous (photo)electrochemical CO2 reduction is discussed through the lens of two experimental systems: pyridine (Py)-catalyzed CO2 (photo)electrochemical reduction at p-GaP photoelectrodes and electrochemical CO2 reduction at Cu electrodes. We close by proposing strategies and principles for the future design of (photo)electrochemical catalysts to improve the selectivity and reaction kinetics of CO2 reduction.

S. Waldvogel, S. Lips, M. Selt et al.

Chemical Reviews • 2018

Arylated products are found in various fields of chemistry and represent essential entities for many applications. Therefore, the formation of this structural feature represents a central issue of contemporary organic synthesis. By the action of electricity the necessity of leaving groups, metal catalysts, stoichiometric oxidizers, or reducing agents can be omitted in part or even completely. The replacement of conventional reagents by sustainable electricity not only will be environmentally benign but also allows significant short cuts in electrochemical synthesis. In addition, this methodology can be considered as inherently safe. The current survey is organized in cathodic and anodic conversions as well as by the number of leaving groups being involved. In some electroconversions the reagents used are regenerated at the electrode, whereas in other electrotransformations free radical sequences are exploited to afford a highly sustainable process. The electrochemical formation of the aryl-substrate bond is discussed for aromatic substrates, heterocycles, other multiple bond systems, and even at saturated carbon substrates. This survey covers most of the seminal work and the advances of the past two decades in this area.

Thanh-Hai Le, Yukyung Kim, Hyeonseok Yoon

Polymers • 2017

Conducting polymers (CPs) have received much attention in both fundamental and practical studies because they have electrical and electrochemical properties similar to those of both traditional semiconductors and metals. CPs possess excellent characteristics such as mild synthesis and processing conditions, chemical and structural diversity, tunable conductivity, and structural flexibility. Advances in nanotechnology have allowed the fabrication of versatile CP nanomaterials with improved performance for various applications including electronics, optoelectronics, sensors, and energy devices. The aim of this review is to explore the conductivity mechanisms and electrical and electrochemical properties of CPs and to discuss the factors that significantly affect these properties. The size and morphology of the materials are also discussed as key parameters that affect their major properties. Finally, the latest trends in research on electrochemical capacitors and sensors are introduced through an in-depth discussion of the most remarkable studies reported since 2003.

M. P. Browne, Edurne Redondo, M. Pumera

Chemical Reviews • 2020

Additive manufacturing (also known as three-dimensional (3D) printing) is being extensively utilized in many areas of electrochemistry to produce electrodes and devices, as this technique allows for fast prototyping and is relatively low cost. Furthermore, there is a variety of 3D-printing technologies available, which include fused deposition modeling (FDM), inkjet printing, select laser melting (SLM), and stereolithography (SLA), making additive manufacturing a highly desirable technique for electrochemical purposes. In particular, over the last number of years, a significant amount of research into using 3D printing to create electrodes/devices for electrochemical energy conversion and storage has emerged. Strides have been made in this area; however, there are still a number of challenges and drawbacks that need to be overcome in order to 3D print active and stable electrodes/devices for electrochemical energy conversion and storage to rival that of the state-of-the-art. In this Review, we will give an overview of the reasoning behind using 3D printing for these electrochemical applications. We will then discuss how the electrochemical performance of the electrodes/devices are affected by the various 3D-printing technologies and by manipulating the 3D-printed electrodes by post modification techniques. Finally, we will give our insights into the future perspectives of this exciting field based on our discussion through this Review.

M. Gaberšček

Nature Communications • 2021

Lithium-based batteries are a class of electrochemical energy storage devices where the potentiality of electrochemical impedance spectroscopy (EIS) for understanding the battery charge storage mechanisms is still to be fully exploited. Generally considered as an ancillary technique, the application of EIS should be promoted focusing on improved experimental design of experiments and advanced data analysis using physics-based models. Electrochemical impedance spectroscopy is a key technique for understanding Li-based battery processes. Here, the authors discuss the current state of the art, advantages and challenges of this technique, also giving an outlook for future developments.

Yuanyuan Jiang, Pengjuan Ni, Chuanxia Chen et al.

Advanced Energy Materials • 2018

Direct electrochemical production of hydrogen peroxide (H2O2) through two‐electron oxygen electrochemistry, for example, the oxygen reduction in fuel cells or water oxidation in water electrolyzers, could provide an attractive alternative to locally produce this chemical on demand. The efficiency of these processes depends greatly on the availability of cost‐effective catalysts with high selectivity, activity, and stability. In recent years, various novel nanostructured materials have been reported to selectively produce H2O2. Through combined experimental and theoretical approaches, underlying mechanisms in the electrochemical synthesis of H2O2 via oxygen electrochemistry have been unveiled. Considering the remarkable progress in this area, the authors summarize recent developments regarding the direct production of H2O2 through two‐electron electrochemical oxygen reactions. The fundamental aspects of electrochemical oxygen reactions are first introduced. Various types of catalysts that can effectively produce H2O2 via two‐electron oxygen electrochemistry are then presented. In parallel, the unique structure‐, component‐, and composition‐dependent electrochemical performance together with the underlying catalytic mechanisms are discussed. Finally, a brief conclusion about the recent progress achieved in electrochemical generation of H2O2 and an outlook on future research challenges are given.

Tammo K. Schwietert, V. Arszelewska, Chao Wang et al.

Nature Materials • 2019

All-solid-state Li-ion batteries promise safer electrochemical energy storage with larger volumetric and gravimetric energy densities. A major concern is the limited electrochemical stability of solid electrolytes and related detrimental electrochemical reactions, especially because of our restricted understanding. Here we demonstrate for the argyrodite-, garnet- and NASICON-type solid electrolytes that the favourable decomposition pathway is indirect rather than direct, via (de)lithiated states of the solid electrolyte, into the thermodynamically stable decomposition products. The consequence is that the electrochemical stability window of the solid electrolyte is notably larger than predicted for direct decomposition, rationalizing the observed stability window. The observed argyrodite metastable (de)lithiated solid electrolyte phases contribute to the (ir)reversible cycling capacity of all-solid-state batteries, in addition to the contribution of the decomposition products, comprehensively explaining solid electrolyte redox activity. The fundamental nature of the proposed mechanism suggests this is a key aspect for solid electrolytes in general, guiding interface and material design for all-solid-state batteries. Although all-solid-state Li-ion batteries exhibit enhanced energy densities, electrochemical stability of solid electrolytes remains a challenge. A mechanism explaining the relationship between redox activity and electrochemical stability for typical solid electrolytes is now proposed.

Ruud Kortlever, Jing Shen, K. Schouten et al.

The Journal of Physical Chemistry Letters • 2015

The electrochemical reduction of CO2 has gained significant interest recently as it has the potential to trigger a sustainable solar-fuel-based economy. In this Perspective, we highlight several heterogeneous and molecular electrocatalysts for the reduction of CO2 and discuss the reaction pathways through which they form various products. Among those, copper is a unique catalyst as it yields hydrocarbon products, mostly methane, ethylene, and ethanol, with acceptable efficiencies. As a result, substantial effort has been invested to determine the special catalytic properties of copper and to elucidate the mechanism through which hydrocarbons are formed. These mechanistic insights, together with mechanistic insights of CO2 reduction on other metals and molecular complexes, can provide crucial guidelines for the design of future catalyst materials able to efficiently and selectively reduce CO2 to useful products.

Zhigang Geng, Yan Liu, Xiangdong Kong et al.

Advanced Materials • 2018

The electrochemical reduction of N2 into NH3 production under ambient conditions represents an attractive prospect for the fixation of N2. However, this process suffers from low yield rate of NH3 over reported electrocatalysts. In this work, a record‐high activity for N2 electrochemical reduction over Ru single atoms distributed on nitrogen‐doped carbon (Ru SAs/N‐C) is reported. At −0.2 V versus reversible hydrogen electrode, Ru SAs/N‐C achieves a Faradaic efficiency of 29.6% for NH3 production with partial current density of −0.13 mA cm−2. Notably, the yield rate of Ru SAs/N‐C reaches 120.9 μgNH3  mgcat.−1  h−1 , which is one order of magnitude higher than the highest value ever reported. This work not only develops a superior electrocatalyst for NH3 production, but also provides a guideline for the rational design of highly active and robust single‐atom catalysts.

Dongbin Xiong, Xifei Li, Z. Bai et al.

Small • 2018

Ti3 C2 Tx , a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti3 C2 Tx directly influence its electrochemical performance, e.g., the use of a well-designed 2D Ti3 C2 Tx as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier/charge-transport kinetics. Some recent progresses of Ti3 C2 Tx MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti3 C2 Tx MXene including supercapacitors, lithium-ion batteries, sodium-ion batteries, and lithium-sulfur batteries. The current opportunities and future challenges of Ti3 C2 Tx MXene are addressed for energy-storage devices. This Review seeks to provide a rational and in-depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti3 C2 Tx , which will promote the further development of 2D MXenes in energy-storage applications.

Yong Yuan, A. Lei

Accounts of Chemical Research • 2019

Oxidative cross-coupling has proved to be one of the most straightforward strategies for forming carbon-carbon and carbon-heteroatom bonds from easily available precursors. Over the past two decades, tremendous efforts have been devoted in this field and significant advances have been achieved. However, in order to remove the surplus electrons from substrates for chemical bonds formation, stoichiometric oxidants are usually needed. Along with the development of modern sustainable chemistry, considerable efforts have been devoted to perform the oxidative cross-coupling reactions under external-oxidant-free conditions. Electrochemical synthesis is a powerful and environmentally benign approach, which can not only achieve the oxidative cross-couplings under external-oxidant-free conditions, but also release valuable hydrogen gas during the chemical bond formation. Recently, the electrochemical oxidative cross-coupling with hydrogen evolution reactions has been significantly explored. This Account presents our recent efforts toward the development of electrochemical oxidative cross-coupling with hydrogen evolution reactions. (1) We explored the oxidative cross-coupling of thiols/thiophenols with arenes, heteroarenes, and alkenes for C-S bond formation. (2) Using the strategy of electrochemical oxidative C-H/N-H cross-coupling with hydrogen evolution, we successfully realized the C-H amination of phenols, anilines, imidazopyridines, and even ethers. (3) Employing halide salts as the green halogenating reagents, we developed a clean C-H halogenation protocol under electrochemical oxidation conditions. To address the limitation that this reaction had to carry out in aqueous solvent, we also developed an alternative method that uses CBr4, CHBr3, CH2Br2, CCl3Br, and CCl4 as halogenating reagents and the mixture of acetonitrile and methanol as cosolvent. (4) We also developed an approach for constructing C-O bonds in a well-developed electrochemical oxidative cross-coupling with hydrogen evolution manner. (5) Under mild external-oxidant-free electrochemical conditions, we realized the C(sp2)-H and C(sp3)-H phosphonylation with modest to high yields. (6) We successfully achieved the S-H/S-H cross-coupling with hydrogen evolution under electrochemical oxidation conditions. By anodic oxidation instead of chemical oxidants, the overoxidation of thiols and thiophenols was well avoided. (7) The methods for constructing structurally diverse heterocyclic compounds were also developed via the electrochemical oxidative annulations. (8) We have also applied the electrochemical oxidative cross-coupling with hydrogen evolution strategy to the alkenes difunctionalization for constructing multiple bonds in one step, such as C-S/C-O bonds, C-S/C-N bonds, C-Se/C-O bonds, and C-Se/C-N bonds. We hope our studies will stimulate the research interest of chemists and pave the way for the discovery of more electrochemical oxidative cross-coupling with hydrogen evolution reactions.

Na Han, P. Ding, Le He et al.

Advanced Energy Materials • 2019

Selective CO2 reduction to formic acid or formate is the most technologically and economically viable approach to realize electrochemical CO2 valorization. Main group metal–based (Sn, Bi, In, Pb, and Sb) nanostructured materials hold great promise, but are still confronted with several challenges. Here, the current status, challenges, and future opportunities of main group metal–based nanostructured materials for electrochemical CO2 reduction to formate are reviewed. Firstly, the fundamentals of electrochemical CO2 reduction are presented, including the technoeconomic viability of different products, possible reaction pathways, standard experimental procedure, and performance figures of merit. This is then followed by detailed discussions about different types of main group metal–based electrocatalyst materials, with an emphasis on underlying material design principles for promoting the reaction activity, selectivity, and stability. Subsequently, recent efforts on flow cells and membrane electrode assembly cells are reviewed so as to promote the current density as well as mechanistic studies using in situ characterization techniques. To conclude a short perspective is offered about the future opportunities and directions of this exciting field.

Joseph Wang

Chemical Reviews • 2008

First-generation glucose biosensors relied on the use of the natural oxygen cosubstrate and the production and detection of hydrogen peroxide and were much simpler, especially when miniaturized sensors are concerned. More sophisticated bioelectronic systems for enhancing the electrical response, based on patterned monolayer or multilayer assemblies and organized enzyme networks on solid electrodes, have been developed for contacting GOx with the electrode support. Electrochemical biosensors are well suited for satisfying the needs of personal (home) glucose testing, and the majority of personal blood glucose meters are based on disposable (screen-printed) enzyme electrode test strips, which are mass produced by the thick film (screen-printing) microfabrication technology. In the counter and an additional “baseline” working electrode, various membranes (mesh) are incorporated into the test strips along with surfactants, to provide a uniform sample coverage. Such devices offer considerable promise for obtaining the desired clinical information in a simpler, user-friendly, faster, and cheaper manner compared to traditional assays. Continuous ex-vivo monitoring of blood glucose was proposed in 1974 and the majority of glucose sensors used for in-vivo applications are based on the GOx-catalyzed oxidation of glucose by oxygen. The major factors that play a role in the development of clinically accurate in-vivo glucose sensors include issues related to biocompatibility, miniaturization, long-term stability of the enzyme and transducer, oxygen deficit, short stabilization times, in-vivo calibration, baseline drift, safety, and convenience.

Yao Zheng, Anthony Vasileff, Xianlong Zhou et al.

Journal of the American Chemical Society • 2019

Electrochemical reduction of CO2 to high-energy-density oxygenates and hydrocarbons beyond CO is important for long-term and large-scale renewable energy storage. However, the key step of the C-C bond formation needed for the generation of C2 products induces an additional barrier on the reaction. This inevitably creates larger overpotentials and greater variety of products as compared to the conversion of CO2 to C1 products. Therefore, an in-depth understanding of the catalytic mechanism is required for advancing the design of efficient electrocatalysts to control the reaction pathway to the desired products. Herein, we present a critical appraisal of reduction of CO2 to C2 products focusing on the connection between the fundamentals of reaction and efficient electrocatalysts. An in-depth discussion of the mechanistic aspects of various C2 reaction pathways on copper-based catalysts is presented together with consideration of practical factors under electrocatalytic operating conditions. By providing some typical examples illustrating the benefit of merging theoretical calculations, surface characterization, and electrochemical measurements, we try to address the key issues of the ongoing debate toward better understanding electrochemical reduction of CO2 at the atomic level and envisioning the roadmap for C2 products generation.

Shuo Wang, Q. Bai, Adelaide M. Nolan et al.

Angewandte Chemie International Edition • 2019

Enabling all-solid-state Li-ion batteries requires solid electrolytes with high Li ionic conductivity and good electrochemical stability. Following recent experimental reports of Li3 YCl6 and Li3 YBr6 as promising new solid electrolytes, we used first principles computation to investigate the Li-ion diffusion, electrochemical stability, and interface stability of chloride and bromide materials and elucidated the origin of their high ionic conductivities and good electrochemical stabilities. Chloride and bromide chemistries intrinsically exhibit low migration energy barriers, wide electrochemical windows, and are not constrained to previous design principles for sulfide and oxide Li-ion conductors, allowing for much greater freedom in structure, chemistry, composition, and Li sublattice for developing fast Li-ion conductors. Our study highlights chloride and bromide chemistries as a promising new research direction for solid electrolytes with high ionic conductivity and good stability.

Yuyan Shao, Jun Wang, Hong Wu et al.

Electroanalysis • 2010

Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). This article selectively reviews recent advances in graphene-based electrochemical sensors and biosensors. In particular, graphene for direct electrochemistry of enzyme, its electrocatalytic activity toward small biomolecules (hydrogen peroxide, NADH, dopamine, etc.), and graphenebased enzyme biosensors have been summarized in more detail; Graphene-based DNA sensing and environmental analysis have been discussed. Future perspectives in this rapidly developing field are also discussed.

Laiquan Li, Cheng Tang, Yao Zheng et al.

Advanced Energy Materials • 2020

The electrochemical reduction of O2 via a two‐electron reaction pathway to H2O2 provides a possibility for replacing the current anthraquinone process, enabling sustainable and decentralized H2O2 production. Here, a nitrogen‐rich few‐layered graphene (N‐FLG) with a tunable nitrogen configuration is developed for electrochemical H2O2 generation. A positive correlation between the content of pyrrolic‐N and the H2O2 selectivity is experimentally observed. The critical role of pyrrolic‐N is elucidated by the variable intermediate adsorption profiles as well as the dependent negative shifts of the pyrrolic‐N peak on X‐ray adsorption near edge structure spectra. By virtue of the optimized N doping configuration and the unique porous structure, the as‐fabricated N‐FLG electrocatalyst exhibits high selectivity toward electrochemical H2O2 synthesis as well as superior long‐term stability. To achieve high‐value products on both the anode and cathode with optimized energy efficiency, a practical device coupling electrochemical H2O2 generation and furfural oxidation is assembled, simultaneously enabling a high yield rate of H2O2 at the cathode (9.66 mol h−1 gcat−1) and 2‐furoic acid at the anode (2.076 mol m−2 h−1) under a small cell voltage of 1.8 V.

Guoqiang Zhao, Kun Rui, S. Dou et al.

Advanced Functional Materials • 2018

Developing sustainable and renewable energy sources along with efficient energy storage and conversion technologies is vital to address environmental and energy challenges. Electrochemical water splitting coupling with grid‐scale renewable energy harvesting technologies is becoming one of the most promising approaches. Besides, hydrogen with the highest mass‐energy density of any fuel is regarded as the ultimate clean energy carrier. The realization of practical water splitting depends heavily on the development of low‐cost, highly active, and durable catalysts for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs). Recently, heterostructured catalysts, which are generally composed of electrochemical active materials and various functional additives, have demonstrated extraordinary electrocatalytic performance toward HER and OER, and particularly a number of precious‐metal‐free heterostructures delivered comparable activity with precious‐metal‐based catalysts. Herein, an overview is presented of recent research progress on heterostructured HER catalysts. It starts with summarizing the fundamentals of HER and approaches for evaluating HER activity. Then, the design and synthesis of heterostructures, electrochemical performance, and the related mechanisms for performance enhancement are discussed. Finally, the future opportunities and challenges are highlighted for the development of heterostructured HER catalysts from the points of view of both fundamental understandings and practical applications.

Abhishek Sarkar, Qingsong Wang, Alexander Schiele et al.

Advanced Materials • 2019

High‐entropy materials, especially high‐entropy alloys and oxides, have gained significant interest over the years due to their unique structural characteristics and correlated possibilities for tailoring of functional properties. The developments in the area of high‐entropy oxides are highlighted here, with emphasis placed on their fundamental understanding, including entropy‐dominated phase‐stabilization effects and prospective applications, e.g., in the field of electrochemical energy storage. Critical comments on the different classes of high‐entropy oxides are made and the underlying principles for the observed properties are summarized. The diversity of materials design, provided by the entropy‐mediated phase‐stabilization concept, allows engineering of new oxide candidates for practical applications, warranting further studies in this emerging field of materials science.

Shaohua Chen, L. Qiu, Hui‐Ming Cheng

Chemical Reviews • 2020

Advanced electrochemical energy storage devices (EESDs) that can store electrical energy efficiently while being miniature/flexible/wearable/load-bearing are much needed for various applications ranging from flexible/wearable/portable electronics to lightweight electric vehicles/aerospace equipment. Carbon-based fibers hold great promise in the development of these advanced EESDs (e.g., supercapacitors and batteries) due to their being lightweight, high electrical conductivity, excellent mechanical strength, flexibility, and tunable electrochemical performance. This review summarizes the fabrication techniques of carbon-based fibers, especially carbon nanofibers, carbon-nanotube-based fibers, and graphene-based fibers, and various strategies for improving their mechanical, electrical, and electrochemical performance. The design, assembly, and potential applications of advanced EESDs from these carbon-based fibers are highlighted. Finally, the challenges and future opportunities of carbon-based fibers for advanced EESDs are discussed.

Lei Fan, Chuan Xia, Peng Zhu et al.

Nature Communications • 2020

Electrochemical CO2 reduction reaction (CO2RR) to liquid fuels is currently challenged by low product concentrations, as well as their mixture with traditional liquid electrolytes, such as KHCO3 solution. Here we report an all-solid-state electrochemical CO2RR system for continuous generation of high-purity and high-concentration formic acid vapors and solutions. The cathode and anode were separated by a porous solid electrolyte (PSE) layer, where electrochemically generated formate and proton were recombined to form molecular formic acid. The generated formic acid can be efficiently removed in the form of vapors via inert gas stream flowing through the PSE layer. Coupling with a high activity (formate partial current densities ~450 mA cm−2), selectivity (maximal Faradaic efficiency ~97%), and stability (100 hours) grain boundary-enriched bismuth catalyst, we demonstrated ultra-high concentrations of pure formic acid solutions (up to nearly 100 wt.%) condensed from generated vapors via flexible tuning of the carrier gas stream. Electrochemical CO2 reduction to liquid fuels is limited by low product concentrations and formation of mixtures with traditional liquid electrolytes. Here the authors report an all-solid-state system for a continuous generation of high-purity and high-concentration formic acid vapors and solutions.

Hao Wang, Jianmin Li, Ke Li et al.

Chemical Society Reviews • 2020

Transition metal nitrides (TMNs), by virtue of their unique electronic structure, high electrical conductivity, superior chemical stability, and excellent mechanical robustness, have triggered tremendous research interest over the past decade, and showed great potential for electrochemical energy conversion and storage. However, bulk TMNs usually suffer from limited numbers of active sites and sluggish ionic kinetics, and eventually ordinary electrochemical performance. Designing nanostructured TMNs with tailored morphology and good dispersity has proved an effective strategy to address these issues, which provides a larger specific surface area, more abundant active sites, and shorter ion and mass transport distances over the bulk counterparts. Herein, the most up-to-date progress on TMN-based nanomaterials is comprehensively reviewed, focusing on geometric-structure design, electronic-structure engineering, and applications in electrochemical energy conversion and storage, including electrocatalysis, supercapacitors, and rechargeable batteries. Finally, we outline the future challenges of TMN-based nanomaterials and their possible research directions beyond electrochemical energy applications.

Lei Fan, Chuan Xia, Fangqi Yang et al.

Science Advances • 2020

Recent progress about electrochemical CO2 reduction toward C2+ products is reviewed. In light of environmental concerns and energy transition, electrochemical CO2 reduction (ECR) to value-added multicarbon (C2+) fuels and chemicals, using renewable electricity, presents an elegant long-term solution to close the carbon cycle with added economic benefits as well. However, electrocatalytic C─C coupling in aqueous electrolytes is still an open challenge due to low selectivity, activity, and stability. Design of catalysts and reactors holds the key to addressing those challenges. We summarize recent progress in how to achieve efficient C─C coupling via ECR, with emphasis on strategies in electrocatalysts and electrocatalytic electrode/reactor design, and their corresponding mechanisms. In addition, current bottlenecks and future opportunities for C2+ product generation is discussed. We aim to provide a detailed review of the state-of-the-art C─C coupling strategies to the community for further development and inspiration in both fundamental understanding and technological applications.

Il-Hoon Cho, Dong Hyung Kim, Sangsoo Park

Biomaterials Research • 2020

Background The electrochemical biosensor is one of the typical sensing devices based on transducing the biochemical events to electrical signals. In this type of sensor, an electrode is a key component that is employed as a solid support for immobilization of biomolecules and electron movement. Thanks to numerous nanomaterials that possess the large surface area, synergic effects are enabled by improving loading capacity and the mass transport of reactants for achieving high performance in terms of analytical sensitivity. Main body We categorized the current electrochemical biosensors into two groups, carbon-based (carbon nanotubes and graphene) and non-carbon-based nanomaterials (metallic and silica nanoparticles, nanowire, and indium tin oxide, organic materials). The carbon allotropes can be employed as an electrode and supporting scaffolds due to their large active surface area as well as an effective electron transfer rate. We also discussed the non-carbon nanomaterials that are used as alternative supporting components of the electrode for improving the electrochemical properties of biosensors. Conclusion Although several functional nanomaterials have provided the innovative solid substrate for high performances, developing on-site version of biosensor that meets enough sensitivity along with high reproducibility still remains a challenge. In particular, the matrix interference from real samples which seriously affects the biomolecular interaction still remains the most critical issues that need to be solved for practical aspect in the electrochemical biosensor.

C. Brett

Molecules • 2022

Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed.

Youbing Li, Huixia Shao, Zifeng Lin et al.

Nature Materials • 2019

Two-dimensional carbides and nitrides of transition metals, known as MXenes, are a fast-growing family of materials that have attracted attention as energy storage materials. MXenes are mainly prepared from Al-containing MAX phases (where A = Al) by Al dissolution in F-containing solution; most other MAX phases have not been explored. Here a redox-controlled A-site etching of MAX phases in Lewis acidic melts is proposed and validated by the synthesis of various MXenes from unconventional MAX-phase precursors with A elements Si, Zn and Ga. A negative electrode of Ti 3 C 2 MXene material obtained through this molten salt synthesis method delivers a Li + storage capacity of up to 738 C g −1 (205 mAh g −1 ) with high charge–discharge rate and a pseudocapacitive-like electrochemical signature in 1 M LiPF 6 carbonate-based electrolyte. MXenes prepared via this molten salt synthesis route may prove suitable for use as high-rate negative-electrode materials for electrochemical energy storage applications. Two-dimensional transition metal carbides and nitrides, known as MXenes, are currently considered as energy storage materials. A generic Lewis acidic etching route for preparing high-rate negative-electrode MXenes with enhanced electrochemical performance in non-aqueous electrolyte is now proposed.

Tyler S. Mathis, Narendra Kurra, Xuehang Wang et al.

Advanced Energy Materials • 2019

Due to the tremendous importance of electrochemical energy storage, numerous new materials and electrode architectures for batteries and supercapacitors have emerged in recent years. Correctly characterizing these systems requires considerable time, effort, and experience to ensure proper metrics are reported. Many new nanomaterials show electrochemical behavior somewhere in between conventional double‐layer capacitor and battery electrode materials, making their characterization a non‐straightforward task. It is understandable that some researchers may be misinformed about how to rigorously characterize their materials and devices, which can result in inflation of their reported data. This is not uncommon considering the current state of the field nearly requires record breaking performance for publication in high‐impact journals. Incorrect characterization and data reporting misleads both the materials and device development communities, and it is the shared responsibility of the community to follow rigorous reporting methodologies to ensure published results are reliable to ensure constructive progress. This tutorial aims to clarify the main causes of inaccurate data reporting and to give examples of how researchers should proceed. The best practices for measuring and reporting metrics such as capacitance, capacity, coulombic and energy efficiencies, electrochemical impedance, and the energy and power densities of capacitive and pseudocapacitive materials are discussed.

Jiahui Wu, Qiaoting Yang, Qian Li et al.

Analytical Chemistry • 2021

Traditional peroxidase-like nanozyme-based sensors suffer from self-decomposition and high toxicity of H2O2, as well as the interference of color from nanozymes themselves and testing samples. In this work, we adopt nanozymes (two-dimension (2D) MnO2 sheets, manganese dioxide nanosheets (MnNS)) with oxidase-like and peroxidase-like properties as advanced catalysts to develop a novel homogeneous electrochemical sensor for organophosphate pesticides (OPs) using dissolved O2 as a coreactant without the interference of H2O2 and color. Owing to the large surface area and unique catalytic activity of MnNS, a large amount of tetramethylbenzidine (TMB) is catalyzed oxidation, leading to a significantly declined differential pulse voltammetry (DPV) current. Obviously, MnNS display an excellent response to thiocholine, deriving from the catalyzing hydrolysis of acetylthiocholine (ATCh) by acetylcholinesterase (AChE), which switches a homogeneous electrochemical OP detection process based on the depressing AChE activity with a limit of detection (LOD) of 0.025 ng mL-1. The as-proposed strategy on using nanozymes with oxidase-like and peroxidase-like properties to develop a homogeneous electrochemical sensor will provide a new pathway for improving the performance of nanozyme-based sensors, and the established MnNS-based homogeneous electrochemical sensor will find more applications for OP residue determination in food samples.