Techniques to Enhance Electrocatalyst Performance in Hydrogen Fuel Cells

The hydrogen oxidation reaction (HOR) is the anodic reaction of hydrogen–oxygen fuel cells, which plays a decisive role in the whole-device performance. However, inexpensive crude hydrogen inevitably contains carbon monoxide (CO) impurities, and even the state-of-the-art platinum (Pt) electrocatalysts can suffer an obvious activity decrease due to the poisoning of active sites, seriously hindering the efficiency of fuel cells. Developing electrocatalysts with promoted CO tolerance necessitates the elucidation of the HOR mechanism and deep understanding of the intrinsic nature of fuel cell poisoning. To date, weakening CO adsorption or accelerating its oxidation could improve the CO tolerance of the catalyst, so it is critical to seek much more effective strategies. Based on the study of the reaction mechanism, this Review summarizes the latest progress of HOR electrocatalysts with high stability and high activity against CO poisoning from two typical theories: hydrogen binding energy theory and bifunctional theory. The strategies for enhancing the CO tolerance of catalysts are gather... Read More

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During the transition from conventional energy sources to sustainable alternatives, the role of energy storage and conversion is pivotal. Unitized regenerative fuel cells (URFCs) have attracted significant attention as promising energy storage and conversion devices owing to their ability to operate in both fuel cell (FC) and electrolyser (EL) modes within a compact single cell. They possess several advantages, including high power density, high specific energy density, light-weight design, low-cost production, high efficiency, long lifespan, and near-zero environmental impact. The development of efficient and durable bifunctional electrocatalysts is essential for the practical implementation and outstanding performance of URFCs. In URFCs, oxygen holds greater significance than hydrogen because its electrochemical reactions at the interface between the electrolyte and the electrode tend to be slow and intricate, primarily due to the pronounced irreversibility of oxygen-related processes. This chapter begins with a brief introduction to various types of FCs, setting the context for th... Read More

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As a clean energy conversion technology, hydrogen fuel cell has great development prospect in the field of sustainable energy. Scientists have been working on the design and optimization of hydrogen fuel cells to make the efficiency and performance higher. This article introduces the main directions and methods of designing and optimizing hydrogen fuel cells. First, the design of hydrogen fuel cell mainly depends on the which catalyst materials you choose and catalyst active sites. For example, precious metal catalysts, transition metal catalysts, and catalysts of nanostructured materials all make a huge impact on battery performance. Improving the activity and stability of catalyst and reducing the cost is one of the key points of this design. In addition, optimizing of the electrolyte film to improve the efficiency and battery life is also key. By taking the above factors into consideration and using advanced materials and technologies, hydrogen fuel cells can achieve high efficiency, high performance, and long life, and promote their commercial application.

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Searching for highly efficient and economical electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial for the development of alkaline polymer membrane fuel cells. Here, we report a valid strategy to active pyrite-type RuS

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Abstract Fuel cell technology, as a new way of energy conversion, is widely used in various fields. At present, the electrocatalyst, as one of the key components of the electrochemical reaction of fuel cells, still suffers from the problems of high cost, low activity and poor stability. Excellent fuel cell electrocatalysts must have excellent catalytic activity, anti‐poisoning ability, electrical conductivity and stability. Metal oxides with corrosion resistance, electrochemical stability and strong metal support interaction effects have been intensively studied. The influence of the synthesis method on the catalytic performance is also crucial. In this review, the importance of fuel cells and their catalysts is introduced. The characteristics of catalysts with three metal oxides, titanium dioxide, cerium dioxide and tungsten oxide, as supports, preparation methods and applications in different fuel cells are reviewed. The synthesis of metal oxide supported catalysts by impregnation, precipitation and hydrothermal methods is described. Finally, the research on metal oxide supported c... Read More

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ConspectusWith the increasing concerns about the energy and environmental crisis, hydrogen, with the high energy density and cleanliness, has been widely regarded as one ideal energy carrier for adjusting the fossil fuel dependent energy system. In this context, extensive studies are focused on improving the efficiency of the sustainable hydrogen production, storage, and utilization coupled with the renewable energy. And it can be realized in electrolysis cells and fuel cell devices. Several electrochemical reactions are involved, such as water splitting (hydrogen/oxygen evolution: HER/OER) for hydrogen production, electroreduction of nitrogen/nitrate, and carbon dioxide to NH3 and HCOOH (NRR, NO3RR, CO2RR) for hydrogen storage, and oxygen reduction reaction (ORR) for hydrogen utilization. However, the achieved efficiency of the hydrogen energy conversion is still unsatisfactory due to these intrinsically sluggish electrochemical reactions, which has spawned a revival of research interests in developing the electrocatalysts with high activity, selectivity, and durability. Therefore, ... Read More

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With much enhanced fuel flexibility to overcome the shortcomings of hydrogen production and storage, high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are still facing challenges of activity loss of oxygen reduction electrocatalyst under the working circumstance of phosphoric acid (PA) electrolyte. Dissolution and leaching of metal component of PtM (M = Cu, Co, Ni···) electrocatalysts is one of the key factors that degrade their initial resistance toward PA and hinder the accessing of activity and durability simultaneously. Here, we report an ultradurable PtRhCu@Pt/C electrocatalyst with a high mass activity of 0.90 A mg–1Pt, which only decreased by 14.4% after 30K ADT cycles in the half-cell and reaches the DOE at 2025 target (<30 mV at 0.8 A cm–2) with 27 mV voltage loss at 0.8 A cm–2 in the single-cell. After adding 0.1 M PA into the electrolyte, the half-wave potential of PtRhCu@Pt/C is negatively shifted by only 52 mV, much lower than that of commercial Pt/C (90 mV). Moreover, the HT-PEMFC assembled by this catalyst delivers a preeminent peak power density of ... Read More

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Hydrogen, characterized by its carbon-neutral attributes and high energy density, is gaining momentum as a promising energy source. Platinum group metal (PGM) catalysts have emerged as pivotal components in water electrolysis and fuel cell technologies. However, their constrained availability and high cost impede the advancement of energy conversion systems. To address these challenges, various strategies have been explored within the realm of PGM catalysts. Particularly noteworthy are catalysts that exhibit an overlayer structure, offering exceptional catalyst utilization efficiency, bimetallic synergies, and strain-induced enhancements. Self-terminated electrodeposition (SED) stands out as a technique that enables precise atomic layer electrodeposition within an aqueous electrolyte environment. It allows meticulous control of metal loading quantities and surface coverage while operating at low temperatures and without the need for vacuum conditions. Catalysts with tailored properties achieved through SED exhibit distinct electrochemical reactivity compared to bulk catalysts, showca... Read More

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This chapter describes the theoretical aspects and main characteristics of fuel cells and electrolyzers, a technological field in constant evolution. Hydrogen can be produced through the electrolysis of water to be stored and subsequently supplied to a fuel cell to obtain electrical energy and water as products. The biggest obstacle for these devices is their cost since they are not yet able to compete economically with more traditional energy technologies. The progress of proton exchange membrane (PEM) fuel cell and PEM electrolyzers is complex and requires significant research on the materials of electrodes (specifically on those were take place the oxygen reduction reaction and the oxygen evolution reaction) membranes and the overall components of both cells. Nevertheless, the development and commercialization of this equipment at market price would give a huge boost to hydrogen systems. Great technical advances have been achieved due to the great effort of researchers in the need to reduce the load of catalysts, enhance the catalytic performance, and improve their components to r... Read More

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Fuel cells are one of the prioritized energy conversion technologies with highly focused research and development. For the whole fuel cell commercial realization on the market, fuel cells must be very affordable. This realization calls for critical developments in addressing the technical hindrance such as the overall fuel cell cost, electrocatalysts stability, and durability. A step towards fuel cell commercialization means well-defined architectural electrocatalysts designs that fully enhance the oxygen reduction reaction and fuel oxidation reaction. The currently pursued electrocatalyst has drawbacks. These include poisoning from methanol and ethanol cross-over, sluggish anodic and cathodic kinetics, air, fuel management, stability, and durability management. This chapter aims to elucidate how the mentioned challenges affect the electrocatalytic activity of the electrocatalysts and expound on some approaches to mitigate the challenges, enhancing adaptability as fuel cells electrocatalysts.

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Abstract In light of the intensifying global energy crisis and the mounting demand for environmental protection, it is of vital importance to develop advanced hydrogen energy conversion systems. Electrolysis cells for hydrogen production and fuel cell devices for hydrogen utilization are indispensable in hydrogen energy conversion. As one of the electrolysis cells, water splitting involves two electrochemical reactions, hydrogen evolution reaction and oxygen evolution reaction. And oxygen reduction reaction coupled with hydrogen oxidation reaction, represent the core electrocatalytic reactions in fuel cell devices. However, the inherent complexity and the lack of a clear understanding of the structure‐performance relationship of these electrocatalytic reactions, have posed significant challenges to the advancement of research in this field. In this work, the recent development in revealing the mechanism of electrocatalytic reactions in hydrogen energy conversion systems is reviewed, including in situ characterization and theoretical calculation. First, the working principles and appl... Read More

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<h2>Summary</h2> Hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) are both two-electron processes that culminate in the formation or consumption of gaseous hydrogen in an electrolyzer or a fuel cell, respectively. Unitized regenerative proton exchange membrane fuel cells merge these two functionalities into one device, allowing to switch between the two modes of operation. This prompts the quest for efficient bifunctional electrode materials catalyzing the HER and HOR with reasonable reaction rates at low overpotentials. In the present study using a data-driven framework, we identify a general criterion for efficient bifunctional performance in the hydrogen electrocatalysis, which refers to a change in the reaction mechanism when switching from cathodic to anodic working conditions. The obtained insight can be used in future studies based on density functional theory to pave the design of efficient HER and HOR catalysts by a dedicated consideration of the kinetics in the analysis of reaction mechanisms.

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The general principles in terms of reactivity and stability to design efficient electrocatalysts for the alkaline hydrogen oxidation reaction are reviewed. The performance of catalysts in anion-exchange membrane fuel cells is further discussed.

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Hydrogen fuel cells, which produce electrical energy and only water as a byproduct, are evaluated for their use in eco-friendly technology. However, there are challenges with using abundant precious metal catalysts for electrodes, particularly regarding hydrogen gas crossover and managing the moisture of the polymer electrolyte membrane. To overcome these challenges, a mediated fuel-cell (MedFC) system, in which hydrogen fuel cells are combined with a redox-flow battery using an oxidation–reduction reaction of an electrolyte, has been recently developed. In a MedFC system, the reduced ions of redox-active materials generated by the oxidation of hydrogen in a packed-bed reactor are fed to the fuel cell electrode as a mediator. In this study, 2,5-dihydroxy1,4-benzoquinone (DHBQ) was used as a anode mediator to operate MedFCs under alkaline conditions. DHBQ and hydrogen were injected with an upward flow into the packed-bed reactor to reduce DHBQ via a chemical reaction. On the anode side of the fuel cell, DHBQ oxidized and transferred the electrons to the cathode. By contrast, an oxygen... Read More

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Research focusing on catalyst layers is critical for enhancing the performance and durability of proton exchange membrane fuel cells.

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Abstract Anion exchange membrane fuel cells (AEMFCs) have been hailed as a promising hydrogen energy technology due to high energy conversion efficiency, zero carbon emission and the potential independence on scare and expensive noble metal electrocatalysts. A variety of platinum group metal (PGM)‐free catalysts has been developed with superior catalytic performance to noble metal benchmarks toward cathodic oxygen reduction reactions (ORR). However, PGM electrocatalysts still dominate the anodic catalyst research because the kinetics of hydrogen oxidation reaction (HOR) are two or three orders of magnitude slower than in that acidic media. Therefore, it is urgently desirable to improve noble metal utilization efficiency and/or develop high‐performance PGM‐free electrocatalysts for HOR, thus promoting the real‐world implementation of AEMFCs. In this review, the current research progress of electrocatalysts for HOR in alkaline media is summarized. We start with the discussion on the current HOR reaction mechanisms and existing controversies. Then, methodologies to improve the HOR perfo... Read More

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Development of highly active, stable, and economic electrocatalyst for sustainable hydrogen (H2) production is crucial in the water electrolysis. In this work, a very effective and affordable electrocatalyst for hydrogen...

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The development of efficient electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) is pivotal for advancing cleaner and sustainable fuel production technologies.

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There is a need for flexible and efficient storage facilities so that the integration of renewable energies and thus the energy transition can succeed. Intermediate storage of energy in the form of hydrogen by electrolysers and effective reconversion to electricity by fuel cells is a possibility. The unitized regenerative fuel cell (URFC) is a single-unit device that combines an electrolyser and a fuel cell, which makes the system costs much cheaper compared to two separate devices. Currently, the focus of URFC research, similar to proton exchange membrane (PEM) electrolysers, is on the development of new catalysts and electrodes with the aim of reducing costs through manufacturing and design optimization [1,2]. In this context, equally important is the increase of electrochemical activity on the oxygen side since oxygen evolution (OER) and oxygen reduction (ORR) are the speed-determining steps comparatively to their counter reactions on the hydrogen side. Due to high potentials and the corrosive oxygen atmosphere, there are additional requirements for electrode stability on the oxyg... Read More

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Proton exchange membrane fuel cell converts hydrogen and oxygen into electricity with zero emission. The high cost and low durability of Pt-based electrocatalysts for oxygen reduction reaction hinder its wide applications. The development of non-precious metal electrocatalysts also reaches the bottleneck because of the low activity and durability. Here we rationally design a hybrid electrocatalyst consisting of atomically dispersed Pt and Fe single atoms and Pt-Fe alloy nanoparticles. The Pt mass activity of the hybrid catalyst is 3.7 times higher than that of commercial Pt/C in a fuel cell. More importantly, the fuel cell with an ultra-low Pt loading in the cathode (0.015 mg Pt cm -2 ) shows excellent durability, with 97 % activity retention after 100,000 cycles and no noticeable current drop at 0.6 V for over 200 h. These results highlight the importance of the synergistic effects among active sites in hybrid electrocatalysts and provide an alternative way to design more active and durable low-Pt electrocatalysts for electrochemical devices.

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