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Introduction The Royal Society of Chemistry Faraday Discussions are a series of meetings focusing on rapidly developing areas of physical chemistry. Contrary to typical conferences, Faraday Discussions rely on the active participation of speakers and audience alike. Topics for each session are based on new research papers submitted specifically for the meeting. Audience participation is...
Introduction The third UK Energy Storage Conference (UKES2016) was held at the Edgbaston campus of the University of Birmingham, UK, from midday on Wednesday 30th November to midday on Friday 2nd December 2016. The aim of the conference, organised by the Energy Storage Research Network on behalf of the UK Research Council funded Energy SuperStore Hub and chaired by Professor Nigel Brandon...
Lithium Sulfur: Mechanism, Modelling and Materials (Li-SM3) was organised by Oxis Energy Ltd, UK, Imperial College London, UK, and the Joint Center for Energy Storage Research (JCESR), USA. It was held at the Institution of Engineering and Technology (IET), Savoy Place, London from 26th–27th April 2017. More than 150 researchers from around the world attended this event, 44 of them...
Rechargeable metal-oxygen cells could exceed the stored energy of today’s most advanced lithium-ion cells. However challenges exist that must be overcome to bring this technology into practical application. These challenges include, among others, the recharge and cyclability efficiency, materials development and improvements in fundamental understanding of the electrochemistry and chemistry inside the cell. The common challenges for the anode, including corrosion, passivation and dendrite formation and those for the air cathode and the electrolyte are summarised in this review for cells based on magnesium, calcium, aluminium, silicon, zinc and iron.
Historically, Johnson Matthey has had a long association with electrochemistry, and perhaps this was inevitable because of the importance of the platinum group metals (pgm) to Johnson Matthey’s early development. Platinum, in particular, has been incredibly useful in the field, because of its exceptional electrocatalytic activity and impressive inertness in most environments. Famously,...
Introduction “Electrochemistry: Volume 14” is a collated book of five papers edited by Craig Banks (Manchester Metropolitan University, UK) and Steven McIntosh (Lehigh University, Bethlehem PA, USA), both of whom are well established in the field with research interests covering the topics in the book. The book is one of a series which aims to collate and summarise the key topics receiving...
Chemically regenerative redox cathode (CRRC) polymer electrolyte fuel cells (PEFCs) are attracting more interest as a platinum-free PEFC technology. These fuel cells utilise a liquid catalyst or catholyte, to perform the indirect reduction of oxygen, eliminating the major degradation mechanisms that plague PEFC durability. A key component of a CRRC PEFC system is the catholyte. This article reports a thorough study of the effect of catholyte concentration and temperature on CRRC PEFC system performance for H7PV4Mo8O40 and Na4H3PV4Mo8O40, two promising polyoxometalate (POM)-based catholytes. The results suggest 80°C and a catholyte concentration of 0.3 M provide the optimum performance for both H7PV4Mo8O40 and Na4H3PV4Mo8O40 (for ambient pressure operation).
To date, the world has been making a massive shift away from fossil fuels towards cleaner energy sources. For the past decade, polymer electrolyte membrane fuel cells (PEMFCs) powered by hydrogen have attracted much attention as a promising candidate for eco-friendly vehicles, i.e. fuel cell electric vehicles (FCEVs), owing to their high power density, high efficiency and zero emission features. Since the world’s first mass production of Tucson ix35 FCEV by Hyundai in 2013, global automotive original equipment manufacturers (OEMs) have focused on commercialising FCEVs. In 2018, Hyundai also unveiled the second generation of the mass-produced FCEV (i.e. Nexo) with improved performances and durability compared with its predecessor. Since then, the global market for PEMFCs for a variety of FCEV applications has been growing very rapidly in terms of both passenger vehicles and medium- and heavy-duty vehicles such as buses and trucks, which require much higher durability than passenger vehicles, i.e. 5000 h for passenger vehicles vs. 25,000 h for heavy-duty vehicles. In addition, PEMFCs are also in demand for other applications including fuel cell electric trains, trams, forklifts, power generators and vessels. We herein present recent advances in how hydrogen and PEMFCs will power the future in a wide range of applications and address key challenges to be resolved in the future.
Electrochemistry studies on the derivatives of graphene have been in the forefront of chemical research in recent years. The large specific surface area, high electrical conductivity, fast electron transfer rate and excellent biocompatibility to biomolecules constitute a few of the underlying reasons for the extensive application of graphene derivatives in modern electrochemistry and related technologies. Much interest in graphene derivatives has been driven by the ease of intentional functionalisation of the carbon backbone of graphene with dopants, such as nitrogen. Doping enhances the electrical conductivity and biocompatibility of nitrogen-doped graphene (NGr) nanomaterials and aids in their potential applications in electrochemical sensing and spectroelectrochemical devices. Despite the application of NGr in electrochemical sensing devices, the major challenge for reproducible industrial application still lies in the use of surfactants and binders and the limited knowledge on the correlation between the N-configurations and the electrocatalytic performance of these NGr-based electrodes. Therefore, the purpose of this short review article is to highlight some recent progress on the application of NGr derivatives for electrochemical detection of biomarkers such as uric acid and dopamine. The paper will also illustrate design parameters for new surfactant-free two-dimensional (2D) N-doped graphene based electrochemical sensors with variable N-functionalities for the detection of dopamine and uric acid.
“Electrolytes for Lithium and Lithium-Ion Batteries”, published in 2014 by Springer, is Volume 58 in the Modern Aspects of Electrochemistry series. The volume is edited by T. Richard Jow, Kang Xu, Oleg Borodin and Makoto Ue. In the preface the Editors set out their purpose in compiling this volume, which was to provide a comprehensive overview of electrolytes for lithium-ion batteries. It covers electrolyte research and development in the last ten years and may be used as a foundation for future work and directions. The volume succeeds in covering the multifaceted area of electrolytes in a logical and highly comprehensive manner.
Chapter topics include lithium salts, advances in solvents, additives and ionic liquids, then progressing to understanding of the cathode and anode interphases, reviewing various characterisation approaches, a discussion of modelling approaches and finally future technologies such as lithium air batteries.
“Nanomaterials for Lithium-Ion Batteries: Fundamentals and Applications” is edited by Rachid Yazami and is published by Pan Stanford Publishing Pte Ltd. The book covers the latest developments in new materials for lithium-ion batteries including examples of novel alloys, oxides and conversion materials for use as anodes and phosphates, high voltage spinels and layered oxides for use as cathodes. Composite structures incorporating reduced graphene oxide are considered along with thin films and nanowires. Emphasis is also placed on combining electrochemical test data with materials characterisation and detailed explanation of the mechanisms occurring.
It may surprise some readers to see an edition of this journal dedicated largely to lithium-ion batteries, but this is a technology that Johnson Matthey considers a major new business area for the company. Johnson Matthey has been involved in research and development (R&D) in the battery materials space for several years and launched its commercial business operations in the sector in...
Angel Cuesta is a Senior Lecturer at the University of Aberdeen, UK. His research is of interest in the field of materials for electrochemical applications and focuses on combining classical electrochemical techniques, in situ vibrational and optical spectroscopy and in situ scanning probe microscopy to obtain as detailed a description as possible, at the molecular level, of the...
To combat the global problem of carbon dioxide emissions, hydrogen is the desired energy vector for the transition to environmentally benign fuel cell power. Water electrolysis (WE) is the major technology for sustainable hydrogen production. Despite the use of renewable solar and wind power as sources of electricity, one of the main barriers for the widespread implementation of WE is the scarcity and high cost of platinum group metals (pgms) that are used to catalyse the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Hence, the critical pgm-based catalysts must be replaced with more sustainable alternatives for WE technologies to become commercially viable. This critical review describes the state-of-the-art pgm-free materials used in the WE application, with a major focus on phosphides and borides. Several emerging classes of HER and OER catalysts are reviewed and detailed structure–property correlations are comprehensively summarised. The influence of the crystallographic and electronic structures, morphology and bulk and surface chemistry of the catalysts on the activity towards OER and HER is discussed.
Following the development of commercial secondary lithium-ion batteries (LIBs), this article illustrates the progress of therein-utilised anode materials from the first successful commercialisation to recent research activities. First, early scientific achievements and industrial developments in the field of LIBs, which enabled the remarkable evolution within the last 20 years of this class of batteries, are reviewed. Afterwards, the characteristics of state-of-the-art commercially available anode materials are highlighted with a particular focus on their lithium storage mechanism. Finally, a new class of anode active materials exhibiting a different storage mechanism, namely combined conversion and alloying, is described, which might successfully address the challenges and issues LIB anodes are currently facing.
Developing novel hydrogen evolution reaction (HER) catalysts with high activity, high stability and low cost is of great importance for the applications of hydrogen energy. In this work, iridium-nickel thin films were electrodeposited on a copper foam as electrocatalyst for HER, and electrodeposition mechanism of iridium-nickel film was studied. The morphology and chemical composition of thin films were determined by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), respectively. The electrocatalytic performances of the films were estimated by linear sweep voltammograms (LSV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results show that iridium-nickel thin films were attached to the substrate of porous structure and hollow topography. The deposition of nickel was preferable in the electrolyte without the addition of additives, and the iridium-nickel thin film was alloyed, resulting in a high deposition rate for Ir42Ni58 thin film, and subsequently an increase of iridium content in the thin films of Ir80Ni20 and Ir88Ni12. Iridium-nickel thin films with Tafel slopes of 40–49 mV dec–1 exhibited highly efficient electrocatalytic activity for HER. The electrocatalytic activity of iridium-nickel thin films showed a loading dependence. As the solution temperature increased from 20°C to 60°C, the hydrogen evolution performance of iridium-nickel thin films improved. The apparent activation energy value of Ir88Ni12 film was 7.1 kJ mol–1. Long-term hydrogen evolution tests exhibited excellent electrocatalytic stability in alkaline solution.
Palladium based membranes are widely used for supplying ultra-high purity hydrogen to a polymer electrolyte fuel cell (PEFC) installed on small vehicles and various electronic devices. Compared to pressure swing adsorption (PSA), the use of palladium based membrane is more economical for small size (small capacity) applications. The transportation of hydrogen through a palladium based membrane is governed by Sieverts’ Law and quantified with Fick’s First Law. Since the 20th century, the fabrication of high-performance palladium based membrane for enhanced hydrogen recovery performance has become practical. However, along with the improvement in hydrogen recovery performance, concentration polarisation becomes unavoidable because hydrogen permeation flux starts to affect hydrogen concentration at the membrane surface. Various parametric studies have investigated the effects of membrane thickness, hydrogen molar fraction and total upstream and downstream pressures on concentration polarisation level. The influence of membrane temperature, permeability, type and number of species in the hydrogen mixture, diffusivity of the hydrogen mixture, system configurations and flow patterns are also reported and comprehensively reviewed in this paper. Part II will complete the presentation.
Recently lithium-ion batteries have started to be used in a number of automotive passenger car applications. This paper will review these applications and compare the requirements of the applications with the capabilities of the lithium-ion chemistries that are actually being used. The gaps between these requirements and capabilities will be highlighted and future developments that may be able to fill these gaps will be discussed. It is concluded that while improvements to the lithium-ion cell chemistry will help reduce the weight of battery packs for electric vehicle applications the largest weight gains will come from the pack design.
This article completes the presentation of various techniques reducing concentration polarisation in palladium based membranes for supplying ultra-high purity hydrogen to a polymer electrolyte fuel cell (PEFC), such as the implementation of baffles and the use of microchannel configuration. The present paper also reviews and reports the current methods for estimating hydrogen permeation flux under concentration polarisation influence, which will be a useful guide for academics and industrial practitioners.
Portable electronic devices, electric vehicles and stationary energy storage applications, which encourage carbon-neutral energy alternatives, are driving demand for batteries that have concurrently higher energy densities, faster charging rates, safer operation and lower prices. These demands can no longer be met by incrementally improving existing technologies but require the discovery of new materials with exceptional properties. Experimental materials discovery is both expensive and time consuming: before the efficacy of a new battery material can be assessed, its synthesis and stability must be well-understood. Computational materials modelling can expedite this process by predicting novel materials, both in stand-alone theoretical calculations and in tandem with experiments. In this review, we describe a materials discovery framework based on density functional theory (DFT) to predict the properties of electrode and solid-electrolyte materials and validate these predictions experimentally. First, we discuss crystal structure prediction using the ab initio random structure searching (AIRSS) method. Next, we describe how DFT results allow us to predict which phases form during electrode cycling, as well as the electrode voltage profile and maximum theoretical capacity. We go on to explain how DFT can be used to simulate experimentally measurable properties such as nuclear magnetic resonance (NMR) spectra and ionic conductivities. We illustrate the described workflow with multiple experimentally validated examples: materials for lithium-ion and sodium-ion anodes and lithium-ion solid electrolytes. These examples highlight the power of combining computation with experiment to advance battery materials research.
With the electric vehicle (EV) market set to grow rapidly over the coming years, the industry faces a challenging ramp-up of volume and material performance demands. From the current trend towards high-energy high-nickel cathode materials, driven in-part by consumer range anxiety, to the emergence of solid-state and beyond lithium-ion technologies, herein we review the changing requirements for active materials in automotive Li-ion battery (LIB) applications, and how science and industry are set to respond.
Introduction The Americas International Meeting on Electrochemistry and Solid State Science was a joint international conference of the 234th Meeting of The Electrochemical Society (ECS), the XXXIII Congreso de la Sociedad Mexicana de Electroquimica (SMEQ) and the 11th Meeting of the Mexico Section of the Electrochemical Society. It was well attended with worldwide representation including...
The market for hydrogen fuel cell vehicles (FCVs) continues to grow worldwide. At present, early adopters rely on a sparse refuelling infrastructure, and there is only limited knowledge about how they evaluate the geographic arrangement of stations when they decide to get an FCV, which is an important consideration for facilitating widespread FCV diffusion. To address this, we conducted several related studies based on surveys and interviews of early FCV adopters in California, USA, and a participatory geodesign workshop with hydrogen infrastructure planning stakeholders in Connecticut, USA. From this mixed-methods research project, we distil 15 high-level findings for planning hydrogen station infrastructure to encourage FCV adoption.
Proteolytic and lipolytic extremely halophilic archaea found in curing salt may contaminate skins during the brine curing process and damage skin structure. In the present study, three proteolytic and lipolytic extremely halophilic archaea were isolated from deteriorated salted sheepskins and characterised using conventional and molecular methods. Each test strain (Haloarcula salaria AT1, Halobacterium salinarum 22T6, Haloarcula tradensis 7T3), a mixed culture of these strains and the mixed culture treated with 1.5 A direct current (DC) were used for brine curing processes of fresh sheepskins and examined during 47 days of storage to evaluate the degree of destruction wreaked by these microorganisms. Both organoleptic properties and scanning electron microscopy (SEM) images of sheepskins proved that each separate test strain and the mixed culture caused serious damage. However, the mixed culture of strains treated with electric current did not damage sheepskin structure. Therefore, we highly recommend sterilisation of brine using DC to prevent archaeal damage on cured hides and skins in the leather industry.
The status, concepts and challenges toward catalysts free of platinum group metal (pgm) elements for proton-exchange membrane fuel cells (PEMFC) are reviewed. Due to the limited reserves of noble metals in the Earth’s crust, a major challenge for the worldwide development of PEMFC technology is to replace Pt with pgm-free catalysts with sufficient activity and stability. The priority target is the substitution of cathode catalysts (oxygen reduction) that account for more than 80% of pgms in current PEMFCs. Regarding hydrogen oxidation at the anode, ultralow Pt content electrodes have demonstrated good performance, but alternative non-pgm anode catalysts are desirable to increase fuel cell robustness, decrease the H2 purity requirements and ease the transition from H2 derived from natural gas to H2 produced from water and renewable energy sources.
The Ulm Electrochemical Talks are held annually in Ulm, Germany. The 14th meeting, held from 23rd–26th June, 2014, focused on the topic of “Next Generation Electrochemical Energy Technologies”. Fuel cells and batteries are described as the dominant technologies to deliver the e-mobility vision within the next few decades. This selective review will focus on battery technologies and supercapacitors; although there was also plenty of material on the equally important topic of fuel cells which is not covered here.
Despite considerable research efforts, finding a chemically stable electrolyte mixture in the presence of reduced oxygen species remains a great challenge. Previously, dimethyl sulfoxide (DMSO) and sulfolane (tetramethylene sulfone (TMS))-based electrolytes were reported to be stable for lithium air (Li-O2) battery applications. Recently lithium hydroxide (LiOH) based chemistries have been demonstrated to involve supressed side reactions in water-added ether- and DMSO-based electrolytes. Herein, we investigate the impact of DMSO-based electrolyte and sulfolane co-solvent on cell chemistry in the presence of water. We found that DMSO-based electrolyte leads to formation of a peroxide-hydroxide mixture as discharge products and the removal of both LiOH and lithium peroxide (Li2O2) on charging from 3.2–3.6 V (vs. Li+/Li) is observed. In the presence of sulfolane as co-solvent, a mixture of Li2O2 and LiOH is formed as major discharge products with slightly more LiOH formation than in the absence of sulfolane. The presence of sulfolane has also significant effects on the charging behaviour, exhibiting a clearer 3 e−/O2 oxygen evolution reaction profile during the entire charging process. This work provides insights into understanding the effects of the primary solvent on promoting LiOH formation and decomposition in lithium iodide (LiI) mediated non-aqueous Li-O2 batteries.
All-solid-state batteries, which utilise a solid electrolyte in place of liquid electrolytes, have the potential for higher energy densities and greater safety than current lithium-ion batteries. However they still face many challenges before the technology is ready to be commercialised. This short report summarises the current state of knowledge in all-solid-state batteries including the electrical, electrochemical and mechanical properties of the electrolytes, and the challenges that remain to be overcome in their development and processing.
Introduction The 21st International Conference on Solid State Ionics (SSI-21) was held in Padova, Italy, from 18th to 23rd June, 2017. The conference saw ~1300 people attend over the six days, covering four macro areas: energy and environment communication and robotics biological systems and life sciences fundamental theory. The energy and environment macro area saw 30 topics including:...
Introduction The Eighth International Flow Battery Forum, organised by Swanbarton Ltd, UK, focused on industrial applications of redox flow batteries (RFB). The conference was held from 27th to 29th June 2017 at the Mercure Piccadilly Hotel, Manchester, UK. It was attended by 212 delegates from all over the world, including flow battery developers, material and component suppliers and...
The second workshop on “Durability and Degradation Issues in PEM Electrolysis Cells and its Components” was held at Fraunhofer-Institut für Solare Energiesysteme ISE in Freiburg, Germany, from 16th–17th February 2016. The workshop was organised as part of the European Union (EU)-funded 7th Framework Programme, NOVEL, of which project Johnson Matthey Fuel Cells is a partner, along with...
“Electrochemical Power Sources: Batteries, Fuel Cells, and Supercapacitors” is a comprehensive textbook covering materials, applications and prospects of the aforementioned devices. The high level overview provided makes this book an excellent resource for readers new to electrochemical devices as it avoids going into excessive detail of each material, whilst providing an overall...
Introduction A select group of researchers are profiled here, all of whom are involved in the design and characterisation of materials for electrochemical energy storage and conversion devices. These include a broad range of battery types, fuel cells, supercapacitors, photovoltaics and devices for the production, storage and utilisation of hydrogen. Many are pioneering the use of advanced...
1. Introduction Within the last 20 years, publication numbers in the field of lithium battery research have increased from a few hundred in the mid 1990s to more than 4500 publications in 2013 (Figure 1). It has grown to a major research topic, with many universities, state laboratories and commercial research and development (R&D) facilities involved. The number of meetings dedicated to...
In recent years, sodium-ion batteries (NIBs) have been explored as an alternative technology to lithium-ion batteries (LIBs) due to their cost-effectiveness and promise in mitigating the energy crisis we currently face. Similarities between both battery systems have enabled fast development of NIBs, however, their full commercialisation has been delayed due to the lack of an appropriate anode material. Hard carbons (HCs) arise as one of the most promising materials and are already used in the first generation of commercial NIBs. Although promising, HCs exhibit lower performance compared to commercial graphite used as an anode in LIBs in terms of reversible specific capacity, operating voltage, initial coulombic efficiency and cycling stability. Nevertheless, these properties vary greatly depending on the HC in question, for example surface area, porosity, degree of graphitisation and defect amount, which in turn are dependent on the synthesis method and precursor used. Optimisation of these properties will bring forward the widespread commercialisation of NIBs at a competitive level with current LIBs. This review aims to provide a brief overview of the current understanding of the underlying reaction mechanisms occurring in the state-of-the-art HC anode material as well as their structure-property interdependence. We expect to bring new insights into the engineering of HC materials to achieve optimal, or at least, comparable electrochemical performance to that of graphite in LIBs.
The Hydrogen South Africa (HySA) programme is based upon the beneficiation of South Africa's large platinum group metal (pgm) resources. The present article summarises some of the progress by HySA Systems, one of the three Competence Centres under the HySA Programme, since 2008. Work has been carried out on membrane electrode assembly and stack development for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) for use in combined heat and power (CHP) supplied by natural gas and hydrogen fuelled vehicle (HFV) applications. The emphasis is on improved carbon monoxide tolerance and simplified heat and humidity management, allowing simpler fuel cell systems to be designed. Metal hydrides modified with palladium are being explored as poisoning-tolerant hydrogen storage materials for stationary and special mobile applications, and metal organic frameworks (MOFs) modified with platinum as light-weight hydrogen storage with a high hydrogen storage capacity. Lastly research into hydrogen purification using Pd membrane reactors is focused on membrane support synthesis, hollow fibre seeding and development of the plating procedure.
Traditional microbial synthesis of chemicals and fuels often rely on energy-rich feedstocks such as glucose, raising ethical concerns as they are directly competing with the food supply. Therefore, it is imperative to develop novel processes that rely on cheap, sustainable and abundant resources whilst providing carbon circularity. Microbial electrochemical technologies (MET) offer unique opportunities to facilitate the conversion of chemicals to electrical energy or vice versa, by harnessing the metabolic processes of bacteria to valorise a range of waste products, including greenhouse gases (GHGs). However, the strict growth and nutrient requirements of industrially relevant bacteria, combined with low efficiencies of native extracellular electron transfer (EET) mechanisms, reduce the potential for industrial scalability. In this two-part work, we review the most significant advancements in techniques aimed at improving and modulating the efficiency of microbial EET, giving an objective and balanced view of current controversies surrounding the physiology of microbial electron transfer, alongside the methods used to wire microbial redox centres with the electrodes of bioelectrochemical systems via conductive nanomaterials.
We review recent research into oxides of platinum group metals (pgms), in particular those of ruthenium and iridium, for use as electrocatalysts for the oxygen evolution reaction (OER). These are used in membrane electrode assemblies (MEAs) in devices such as electrolysers, for water splitting to generate hydrogen as fuel, and in fuel cells where they provide a buffer against carbon corrosion. In these situations, proton exchange membrane (PEM) layers are used, and highly acid-resilient electrocatalyst materials are required. The range of structure types investigated includes perovskites, pyrochlores and hexagonal perovskite-like phases, where the pgm is partnered by base metals in complex chemical compositions. The role of chemical synthesis in the discovery of new oxide compositions is emphasised, particularly to yield powders for processing into MEAs. Part I introduces the electrocatalytic splitting of water to oxygen and hydrogen and provides a survey of ruthenium and iridium oxide structures for oxygen evolution reaction catalysis.
It is imperative to develop novel processes that rely on cheap, sustainable and abundant resources whilst providing carbon circularity. Microbial electrochemical technologies (MET) offer unique opportunities to facilitate the conversion of chemicals to electrical energy or vice versa by harnessing the metabolic processes of bacteria to valorise a range of waste products including greenhouse gases (GHGs). Part I (1) introduced the EET pathways, their limitations and applications. Here in Part II, we outline the strategies researchers have used to modulate microbial electron transfer, through synthetic biology and biohybrid approaches and present the conclusions and future directions.
Cathodes for Electrochemical Carbon Dioxide Reduction to Multi-Carbon Products: Part I[67, (1), 97 ]
This is a focused review of recent highlights in the literature in cathode development for low temperature electrochemical carbon dioxide and carbon monoxide reduction to multi-carbon (C2+) products. The major goals for the field are to increase Faradaic efficiency (FE) for specific C2+ products, lower cell voltage for industrially relevant current densities and increase cell lifetime. A key to achieving these goals is the rational design of cathodes through increased understanding of structure-selectivity and structure-activity relationships for catalysts and the influence of catalyst binders and gas diffusion layers (GDLs) on the catalyst microenvironment and subsequent performance.
Bismuth vanadate (BiVO4) is proven to be a promising photocatalyst for water splitting. However, the effect of materials syntheses, electrode preparation and size of photoelectrode on the photocurrent output of BiVO4 photoanodes needs further investigations. In this study, three different BiVO4 nanoparticle synthesis were employed, namely hydrothermal (HT), HT in the presence of ethylene glycol (EG) and HT with the addition of hydrazine hydrate (HH). In addition, two molecular inks (Triton-X and ethyl‐methyl‐imidazole, EMI), were compared for the preparation of BiVO4 photoanodes using a simple doctor-blade technique followed by calcination at 450°C. The photoanodes (9 cm2 active surface) were then compared for their photocurrent density at AM1.5G illumination and 1.2 V (vs . standard hydrogen electrode (SHE)) bias in a specifically designed, three-dimensional (3D)-printed electrochemical cell. The highest photocurrent 0.13 ± 0.1 mA cm–2 was obtained with the EMI ink, whereas tenfold lower photocurrent was obtained with Triton-X due to the higher charge transfer resistance, measured by electric impedance spectroscopy (EIS). The photoresponse was reproducible and relatively stable, with only 8% decrease in five consecutive illumination periods of 1 min.
We continue our review of recent research into oxides of platinum group metals (pgms), in particular those of ruthenium and iridium, for use as electrocatalysts for the oxygen evolution reaction (OER). In Part I (1), the electrocatalytic splitting of water to oxygen and hydrogen was introduced as a key process in developing future devices for various energy-related applications. A survey of ruthenium and iridium oxide structures for oxygen evolution reaction catalysis was presented. Part II discusses mechanistic details and acid stability of pgm oxides and presents the conclusions and outlook. We highlight emerging work that shows how leaching of the base metals from the multinary compositions occurs during operation to yield active pgm-oxide phases, and how attempts to correlate stability with crystal structure have been made. Implications of these discoveries for the balance of activity and stability needed for effective electrocatalysis in real devices are discussed.