IrCuNi Deeply Concave Nanocubes as Highly Active Oxygen Evolution Reaction Electrocatalyst in Acid Electrolyte

Multi-Component and Nanoporous Design toward RuO2-Based Electrocatalyst with Enhanced Performance for Acidic Water Splitting

Developing electrocatalysts with excellent activity and stability for water splitting in acidic media remains a formidable challenge due to the sluggish kinetics and severe dissolution. As a solution, a multi-component doped RuO2 prepared through a process of dealloying-annealing is presented. The resulting multi-doped RuO2 possesses a nanoporous structure, ensuring a high utilization efficiency of Ru. Furthermore, the dopants can regulate the electronic structure, causing electron aggregation around unsaturated Ru sites, which mitigates Ru dissolution and significantly enhances the catalytic stability/activity. The representative catalyst (FeCoNiCrTi-RuO2) shows an overpotential of 167 mV at 10 mA cm-2 for oxygen evolution reaction (OER) in 0.5 m H2SO4 solution with a Tafel slope of 53.1 mV dec-1, which is among the highest performance reported. Moreover, it remains stable for over 200 h at a current density of 10 mA cm-2. This work presents a promising approach for improving RuO2-based electrocatalysts, offering a crucial advancement for electrochemical water splitting.

Recent Research on Iridium-Based Electrocatalysts for Acidic Oxygen Evolution Reaction from the Origin of Reaction Mechanism

As the anode reaction of proton exchange membrane water electrolysis (PEMWE), the acidic oxygen evolution reaction (OER) is one of the main obstacles to the practical application of PEMWE due to its sluggish four-electron transfer process. The development of high-performance acidic OER electrocatalysts has become the key to improving the reaction kinetics. To date, although various excellent acidic OER electrocatalysts have been widely researched, Ir-based nanomaterials are still state-of-the-art electrocatalysts. Hence, a comprehensive and in-depth understanding of the reaction mechanism of Ir-based electrocatalysts is crucial for the precise optimization of catalytic performance. In this review, the origin and nature of the conventional adsorbate evolution mechanism (AEM) and the derived volcanic relationship on Ir-based electrocatalysts for acidic OER processes are summarized and some optimization strategies for Ir-based electrocatalysts based on the AEM are introduced. To further investigate the development strategy of high-performance Ir-based electrocatalysts, several unconventional OER mechanisms including dual-site mechanism and lattice oxygen mediated mechanism, and their applications are introduced in detail. Thereafter, the active species on Ir-based electrocatalysts at acidic OER are summarized and classified into surface Ir species and O species. Finally, the future development direction and prospect of Ir-based electrocatalysts for acidic OER are put forward.

Effect of Selective Metallic Defects on Catalytic Performance of Alloy Nanosheets

Defects in the crystal structure of nanomaterials are important for their diverse applications. As, defects in 2D framework allow surface confinement effects, efficient molecular accessibility, high surface-area to volume-ratio and lead to higher catalytic activity, but it is challenging to expose defects of specific metal on the surface of 2D alloy and find the correlation between defective structure and electrocatalytic properties with atomic precision. Herein, the work paves the way for the controlled synthesis of ultrathin porous Ir-Cu nanosheets (NSs) with selectively iridium (Ir) rich defects to boost their performance for acidic oxygen evolution reaction (OER). X-ray absorption spectroscopy reveals that the oxidized states of Ir in defects of porous NSs significantly impact the electronic structure and decline the energy barrier. As a result, porous Ir-Cu/C NSs deliver improved OER activity with an overpotential of 237 mV for reaching 10 mA cm-2 and exhibit significantly higher mass activity than benchmark Ir/C under acidic conditions. Therefore, the present work highlights the concept of constructing a selective noble metal defect-rich open structure for catalytic applications.

Advances in Noble Metal Electrocatalysts for Acidic Oxygen Evolution Reaction: Construction of Under-Coordinated Active Sites

Renewable energy-driven proton exchange membrane water electrolyzer (PEMWE) attracts widespread attention as a zero-emission and sustainable technology. Oxygen evolution reaction (OER) catalysts with sluggish OER kinetics and rapid deactivation are major obstacles to the widespread commercialization of PEMWE. To date, although various advanced electrocatalysts have been reported to enhance acidic OER performance, Ru/Ir-based nanomaterials remain the most promising catalysts for PEMWE applications. Therefore, there is an urgent need to develop efficient, stable, and cost-effective Ru/Ir catalysts. Since the structure-performance relationship is one of the most important tools for studying the reaction mechanism and constructing the optimal catalytic system. In this review, the recent research progress from the construction of unsaturated sites to gain a deeper understanding of the reaction and deactivation mechanism of catalysts is summarized. First, a general understanding of OER reaction mechanism, catalyst dissolution mechanism, and active site structure is provided. Then, advances in the design and synthesis of advanced acidic OER catalysts are reviewed in terms of the classification of unsaturated active site design, i.e., alloy, core-shell, single-atom, and framework structures. Finally, challenges and perspectives are presented for the future development of OER catalysts and renewable energy technologies for hydrogen production.

Atomically thin iridium nanosheets for oxygen evolution electrocatalysis

2D nanostructures of noble metals hold great potential for developing efficient electrocatalysts due to their high atom efficiency associated with their large specific surface area and abundant active sites. Here, we introduce a one-pot solvothermal synthesis method that can enable the fabrication of freestanding atomically thin Ir nanosheets. The thermal decomposition of a complex of Ir and a long-chain amine, which could readily be formed with the assistance of a strong base, under CO flow conditions successfully yielded Ir nanosheets consisting of 2-4 atomic layers. The prepared Ir nanosheets showed prominent activity and stability toward oxygen evolution electrocatalysis in acidic conditions, which can be attributed to their ultrathin 2D structure.

Design of Superior Electrocatalysts for Proton-Exchange Membrane-Water Electrolyzers: Importance of Catalyst Stability and Evolution

By virtue of the high energy conversion efficiency and compact facility, proton exchange membrane water electrolysis (PEMWE) is a promising green hydrogen production technology ready for commercial applications. However, catalyst stability is a challenging but often-ignored topic for the electrocatalyst design, which retards the device applications of many newly-developed electrocatalysts. By defining catalyst stability as the function of activity versus time, we ascribe the stability issue to the evolution of catalysts or catalyst layers during the water electrolysis. We trace the instability sources of electrocatalysts as the function versus time for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acid and classify them into internal and external sources. Accordingly, we summarize the latest studies for stability improvements into five strategies, i. e., thermodynamic stable active site construction, precatalyst design, support regulation, superwetting electrode fabrication, and catalyst-ionomer interface engineering. With the help of ex-situ/ in-situ characterizations and theoretical calculations, an in-depth understanding of the instability sources benefits the rational development of highly active and stable HER/OER electrocatalysts for PEMWE applications.

Interface Charge Distribution Engineering of Pd-CeO2 /C for Efficient Carbohydrazide Oxidation Reaction

Carbohydrazide electrooxidation reaction (COR) is a potential alternative to oxygen evolution reaction in water splitting process. However, the sluggish kinetics process impels to develop efficient catalysts with the aim of the widespread use of such catalytic system. Since COR concerns the adsorption/desorption of reactive species on catalysts, the electronic structure of electrocatalyst can affect the catalytic activity. Interface charge distribution engineering can be considered to be an efficient strategy for improving catalytic performance, which facilitates the cleavage of chemical bond. Herein, highly dispersed Pd nanoparticles on CeO2 /C catalyst are prepared and the COR catalytic performance is investigated. The self-driven charge transfer between Pd and CeO2 can form the local nucleophilic and electrophilic region, promoting to the adsorption of electron-withdrawing and electron-donating group in carbohydrazide molecule, which facilitates the cleavage of C-N bond and the carbohydrazide oxidation. Due to the local charge distribution, the Pd-CeO2 /C exhibits superior COR catalytic activity with a potential of 0.27 V to attain 10 mA cm-2 . When this catalyst is used for energy-efficient electrolytic hydrogen production, the carbohydrazide electrolysis configuration exhibits a low cell voltage (0.6 V at 10 mA cm-2 ). This interface charge distribution engineering can provide a novel strategy for improving COR catalytic activity.

Metal Alloys-Structured Electrocatalysts: Metal-Metal Interactions, Coordination Microenvironments, and Structural Property-Reactivity Relationships

Metal alloys-structured electrocatalysts (MAECs) have made essential contributions to accelerating the practical applications of electrocatalytic devices in renewable energy systems. However, due to the complex atomic structures, varied electronic states, and abundant supports, precisely decoding the metal-metal interactions and structure-activity relationships of MAECs still confronts great challenges, which is critical to direct the future engineering and optimization of MAECs. Here, this timely review comprehensively summarizes the latest advances in creating the MAECs, including the metal-metal interactions, coordination microenvironments, and structure-activity relationships. First, the fundamental classification, design, characterization, and structural reconstruction of MAECs are outlined. Then, the electrocatalytic merits and modulation strategies of recent breakthroughs for noble and non-noble metal-structured MAECs are thoroughly discussed, such as solid solution alloys, intermetallic alloys, and single-atom alloys. Particularly, unique insights into the bond interactions, theoretical understanding, and operando techniques for mechanism disclosure are given. Thereafter, the current states of diverse MAECs with a unique focus on structural property-reactivity relationships, reaction pathways, and performance comparisons are discussed. Finally, the future challenges and perspectives for MAECs are systematically discussed. It is believed that this comprehensive review can offer a substantial impact on stimulating the widespread utilization of metal alloys-structured materials in electrocatalysis.

Achieving High Activity and Long-Term Stability towards Oxygen Evolution in Acid by Phase Coupling between CeO2-Ir

The development of efficient and stable catalysts with high mass activity is crucial for acidic oxygen evolution reaction (OER). In this study, CeO2-Ir heterojunctions supported on carbon nanotubes (CeO2-Ir/CNTs) are synthesized using a solvothermal method based on the heterostructure strategy. CeO2-Ir/CNTs demonstrate remarkable effectiveness as catalysts for acidic OER, achieving 10.0 mA cm-2 at a low overpotential of only 262.9 mV and maintaining stability over 60.0 h. Notably, despite using an Ir dosage 15.3 times lower than that of c-IrO2, CeO2-Ir/CNTs exhibit a very high mass activity (2542.3 A gIr-1@1.53 V), which is 58.8 times higher than that of c-IrO2. When applied to acidic water electrolyzes, CeO2-Ir/CNTs display a prosperous potential for application as anodic catalysts. X-ray photoelectron spectrometer (XPS) analysis reveals that the chemical environment of Ir nanoparticles (NP) can be effectively modulated through coupling with CeO2. This modulation is believed to be the key factor contributing to the excellent OER catalytic activity and stability observed in CeO2-Ir/CNTs.

Preparation of Ir-Cu/C nanosheets for the oxygen evolution reaction by room temperature plasma carbonization

Ir-Cu/C nanosheets with a thickness of about 2 nm were prepared using Ar plasma carbonization and reduction at room temperature. The obtained Ir-Cu/C catalyst, composed of single atom Ir-doped Cu nanoparticles embedded in a carbon framework, exhibits efficient oxygen evolution reaction activity with a low overpotential.

Understanding the Structural Evolution of IrFeCoNiCu High-Entropy Alloy Nanoparticles under the Acidic Oxygen Evolution Reaction

High-entropy alloy (HEA) nanoparticles are promising catalyst candidates for the acidic oxygen evolution reaction (OER). Herein, we report the synthesis of IrFeCoNiCu-HEA nanoparticles on a carbon paper substrate via a microwave-assisted shock synthesis method. Under OER conditions in 0.1 M HClO₄, the HEA nanoparticles exhibit excellent activity with an overpotential of ∼302 mV measured at 10 mA cm^-2 and improved stability over 12 h of operation compared to the monometallic Ir counterpart. Importantly, an active Ir-rich shell layer with nanodomain features was observed to form on the surface of IrFeCoNiCu-HEA nanoparticles immediately after undergoing electrochemical activation, mainly due to the dissolution of the constituent 3d metals. The core of the particles was able to preserve the characteristic homogeneous single-phase HEA structure without significant phase separation or elemental segregation. This work illustrates that under acidic operating conditions, the near-surface structure of HEA nanoparticles is susceptible to a certain degree of structural dynamics.

Electrocatalysts for the Oxygen Evolution Reaction in Acidic Media

The well-established proton exchange membrane (PEM)-based water electrolysis, which operates under acidic conditions, possesses many advantages compared to alkaline water electrolysis, such as compact design, higher voltage efficiency, and higher gas purity. However, PEM-based water electrolysis is hampered by the low efficiency, instability, and high cost of anodic electrocatalysts for the oxygen evolution reaction (OER). In this review, the recently reported acidic OER electrocatalysts are comprehensively summarized, classified, and discussed. The related fundamental studies on OER mechanisms and the relationship between activity and stability are particularly highlighted in order to provide an atomistic-level understanding for OER catalysis. A stability test protocol is suggested to evaluate the intrinsic activity degradation. Some current challenges and unresolved questions, such as the usage of carbon-based materials and the differences between the electrocatalyst performances in acidic electrolytes and PEM-based electrolyzers are also discussed. Finally, suggestions for the most promising electrocatalysts and a perspective for future research are outlined. This review presents a fresh impetus and guideline to the rational design and synthesis of high-performance acidic OER electrocatalysts for PEM-based water electrolysis.

Sulfur-Induced Low Crystallization of Ultrathin Pd Nanosheet Arrays for Sulfur Ion Degradation-Assisted Energy-Efficient H2 Production

The utilization of thermodynamically favorable sulfur oxidation reaction (SOR) as an alternative to sluggish oxygen evolution reaction is a promising technology for low-energy H₂ production while degrading the sulfur source from wastewater. Herein, amorphous/crystalline S-doped Pd nanosheet arrays on nickel foam (a/c S-Pd NSA/NF) is prepared by S-doping crystalline Pd NSA/NF.  Owing to the ultrathin amorphous nanosheet structure and the incorporation of S atoms, the a/c S-Pd NSA/NF provides a large number of active sitesand the optimized electronic structure, while exhibiting outstanding electrocatalytic activity in hydrogen evolution reaction (HER) and SOR. Therefore, the coupling system consisting of SOR-assisted HER can reach a current density of 100 mA cm^-2 at 0.642 V lower than conventional electrolytic water by 1.257 V, greatly reducing energy consumption. In addition, a/c S-Pd NSA/NF can generate H₂ over a long period of time while degrading S^2- in water to the value-added sulfur powder, thus further reducing the cost of H₂ production. This work proposes an attractive strategy for the construction of an advanced electrocatalyst for H₂ production and utilization of toxic sulfide wastewater by combining S-doping induced partial amorphization and ultrathin metal nanosheet arrays.

Heteroatom Doped Amorphous/Crystalline Ruthenium Oxide Nanocages as a Remarkable Bifunctional Electrocatalyst for Overall Water Splitting

Developing robust and highly active bifunctional electrocatalysts for overall water splitting is critical for efficient sustainable energy conversion. Herein, heteroatom-doped amorphous/crystalline ruthenium oxide-based hollow nanocages (M-ZnRuO_x (MCo, Ni, Fe)) through delicate control of composition and structure is reported. Among as-synthesized M-ZnRuO_x nanocages, Co-ZnRuO_x nanocages deliver an ultralow overpotential of 17 mV at 10 mA cm^-2 and a small Tafel slope of 21.61 mV dec^-1 for hydrogen evolution reaction (HER), surpassing the commercial Pt/C catalyst, which benefits from the synergistic coupling effect between electron regulation induced by Co doping and amorphous/crystalline heterophase structure. Moreover, the incorporation of Co prevents Ru from over-oxidation under oxygen evolution reaction (OER) operation, realizing the leap from a monofunctional to multifunctional electrocatalyst and then Co-ZnRuO_x nanocages exhibit remarkable OER catalytic activity as well as overall water splitting performance. Combining theory calculations with spectroscopy analysis reveal that Co is not only the optimal active site, increasing the number of exposed active sites while also boosting the long-term durability of catalyst by modulating the electronic structure of Ru atoms. This work opens a considerable avenue to design highly active and durable Ru-based electrocatalysts.

High-Valence-Manganese Driven Strong Anchoring of Iridium Species for Robust Acidic Water Oxidation

Designing an efficient and durable electrocatalyst for the sluggish anodic oxygen evolution reaction (OER) has been the primary goal of using proton exchange membrane electrolyzer owing to the highly acidic and oxidative environment at the anode. In this work, it is reported that high-valence manganese drives the strong anchoring of the Ir species on the manganese dioxide (MnO2 ) matrix via the formation of an Mn-O-Ir coordination structure through a hydrothermal-redox reaction. The iridium (Ir)-atom-array array is firmly anchored on the Mn-O-Ir coordination structure, endowing the catalyst with excellent OER activity and stability in an acidic environment. Ir-MnO2 (160)-CC shows an ultralow overpotential of 181 mV at j = 10 mA cm-2 and maintains long-term stability of 180 h in acidic media with negligible decay, superior to most reported electrocatalysts. In contrast, when reacting with low-valence MnO2 , Ir species tend to aggregate into IrOx nanoparticles, leading to poor OER stability. Density functional theory (DFT) calculations further reveal that the formation of the Mn-O-Ir coordination structure can optimize the adsorption strength of *OOH intermediates, thus boosting the acidic OER activity and stability.

Construction of steady-active self-supported porous Ir-based electrocatalysts for the oxygen evolution reaction

Developing highly active and stable oxygen evolution reaction (OER) catalysts for water electrolysis remains a great challenge. A self-supported Ir nanocatalyst was prepared via a self-assembly method. Its porous structure and residual metal incorporation contributed to its high activity and stability for the OER in acid.

Overall Design of Anode with Gradient Ordered Structure with Low Iridium Loading for Proton Exchange Membrane Water Electrolysis

Insufficient catalyst utilization, limited mass transport, and high ohmic resistance of the conventional membrane electrode assembly (MEA) lead to significant performance losses of proton exchange membrane water electrolysis (PEMWE). Herein we propose a novel ordered MEA based on anode with a 3D membrane/catalytic layer (CL) interface and gradient tapered arrays by the nanoimprinting method, confirmed by energy dispersive spectroscopy. Benefiting from the maximized triple-phase interface, rapid mass transport, and gradient CL by overall design, such an ordered structure with Ir loading of 0.2 mg cm^-2 not only greatly increases the electrochemical active area by 4.2 times but also decreases the overpotentials of both mass transport and ohmic polarization by 13.9% and 8.7%, respectively, compared with conventional MEA with an Ir loading of 2 mg cm^-2, thus ensuring a superior performance (1.801 V at 2 A cm^-2) and good stability. This work provides a new strategy of designing MEA for high-performance PEMWE.

Promoting the Electrocatalytic Ethanol Oxidation Activity of Pt by Alloying with Cu

The development and commercialization of direct ethanol fuel cells requires active and durable electro-catalysts towards the ethanol oxidation reactions (EOR). Rational composition and morphology control of Pt-based alloy nanocrystals can not only enhance their EOR reactivity but also reduce the consumption of precious Pt. Herein, PtCu nanocubes (NCs)/CB enclosed by well-defined (100) facets were prepared by solution synthesis, exhibiting much higher mass activity (4.96 A mgPt−1) than PtCu nanoparticles (NPs)/CB with irregular shapes (3.26 A mgPt−1) and commercial Pt/C (1.67 A mgPt−1). CO stripping and in situ Fourier transform infrared spectroscopy (FTIR) experiments indicate that the alloying of Cu enhanced the adsorption of ethanol, accelerated the subsequent oxidation of intermediate species, and increased the resistance to CO poisoning of PtCu NCs/CB, as compared with commercial Pt/C. Therefore, alloying Pt with earth-abundant Cu under rational composition and surface control can optimize its surface and electronic structures and represents a promising strategy to promote the performance of electro-catalysts while reduce the use of precious metals.

Structural engineering and electronic state tuning optimization of molybdenum-doped cobalt hydroxide nanosheet self-assembled hierarchical microtubules for efficient electrocatalytic oxygen evolution

Cobalt-based hydroxide are ideal candidates for the oxygen evolution reaction. Herein, we use molybdenum oxide nanorods as sacrificial templates to construct a self-supporting molybdenum-doped cobalt hydroxide nanosheet hierarchical microtubule structure based on a structural engineering strategy to improve the active area of the catalyst. X-ray-based spectroscopic tests revealed that Mo (VI) with tetrahedral coordination intercalated into the interlayer of cobalt hydroxide, promoting interlayer separation. At the same time, Mo is connected with Co through oxygen bonds, which promotes the transfer of Co charges to Mo and reduces the electron cloud density of Co ions. In 1 M KOH, optimized molybdenum-doped cobalt hydroxide nanosheet microtubules only needs an overpotential of 288 mV to drive a current density of 10 mA cm^-2, which is significantly better than that of pure Co(OH)₂ nanosheets and RuO₂. Structural engineering and electronic state regulation can effectively improve the oxygen evolution activity of cobalt-based hydroxide, which provides a design idea for the development of efficient oxygen evolution catalysts.

Recent Advances Regarding Precious Metal-Based Electrocatalysts for Acidic Water Splitting

Electrochemical water splitting has wide applicability in preparing high-density green energy. The Proton exchange membrane (PEM) water electrolysis system is a promising technique for the generation of hydrogen due to its high electrolytic efficiency, safety and reliability, compactness, and quick response to renewable energy sources. However, the instability of catalysts for electrochemical water splitting under operating conditions limits their practical applications. Until now, only precious metal-based materials have met the requirements for rigorous long-term stability and high catalytic activity under acid conditions. In this review, the recent progress made in this regard is presented and analyzed to clarify the role of precious metals in the promotion of the electrolytic decomposition of water. Reducing precious metal loading, enhancing catalytic activity, and improving catalytic lifetime are crucial directions for developing a new generation of PEM water electrolysis catalysts. A summary of the synthesis of high-performance catalysts based on precious metals and an analysis of the factors affecting catalytic performance were derived from a recent investigation. Finally, we present the remaining challenges and future perspectives as guidelines for practical use.

An amorphous ultrathin iridium/carbon catalyst realizing efficient electrochemical hydrogen evolution

An amorphous 1.1 nm Ir/C catalyst exhibits ultralow overpotentials of 10 and 64 mV for the hydrogen evolution reaction at current densities of 10 and 100 mA cm^-2, together with 117 A mg^-1 mass activity and outstanding long-term durability, superior to those of the commercial Pt/C catalyst.

Amorphous FeNiCu-MOF as highly efficient electrocatalysts for oxygen evolution reaction in alkaline medium

The preparation of low-cost and high-activity oxygen evolution reaction (OER) catalysts is a technical bottleneck in the field of electrolysis of water to produce hydrogen. Amorphous metal-organic frameworks (MOFs) with...

Surface Phase Engineering Modulated Iron-Nickel Nitrides/Alloy Nanospheres with Tailored d-Band Center for Efficient Oxygen Evolution Reaction

The oxygen evolution reaction (OER) plays a key role in many electrochemical energy conversion systems, but it is a kinetically sluggish reaction and requires a large overpotential to deliver appreciable current, especially for the non-noble metal electrocatalysts. In this study, the authors report a surface phase engineering strategy to improve the OER performance of transition metal nitrides (TMNs). The iron-nickel nitrides/alloy nanospheres (FeNi₃ -N) wrapped in carbon are synthesized, and the optimized FeNi₃ -N catalyst displays dual-phase nitrides on the surface induced by atom migration phenomenon, resulting from the different migration rates of metal atoms during the nitridation process. It shows excellent OER performance in alkaline media with an overpotential of 222 mV at 10 mA cm^-2 , a small Tafel slope of 41.53 mV dec^-1 , and long-term durability under high current density (>0.5 A cm^-2 ) for at least 36 h. Density functional theory (DFT) calculations further reveal that the dual-phase nitrides are favorable to decrease the energy barrier, modulate the d-band center to balance the absorption and desorption of the intermediates, and thus promote the OER electrochemical performance. This strategy may shed light on designing OER and other catalysts based on surface phase engineering.

Iridium in Tungsten Trioxide Matrix as an Efficient Bi-Functional Electrocatalyst for Overall Water Splitting in Acidic Media

Electrocatalytic water splitting in acidic media is a promising strategy for grid scale production of hydrogen using renewable energy, but challenges still exist in the development of advanced catalysts with both high activity and stability. Herein, it is reported that iridium doped tungsten trioxide (Ir-doped WO₃ ) with arrayed structure and confined Ir sites is an efficient and durable bi-functional catalyst for overall acidic water splitting. A low overpotential (258 mV) is required to achieve an oxygen evolution reaction current density of 10 mA cm^-2 in 0.5 m H₂ SO₄ solution. Meanwhile, Ir-doped WO₃ processes a similar intrinsic activity to Pt/C toward hydrogen evolution reaction. Overall water splitting using the bi-functional Ir-doped WO₃ catalyst shows low cell voltages of 1.56 and 1.68 V to drive the current densities of 10 and 100 mA cm^-2 , respectively, with only 16 mV decay observed after 60 h continuous electrolysis under the current density of 100 mA cm^-2 . Structural analysis and density functional theory calculation indicate that the adjusted coordination environment of Ir within the crystalline matrix of WO₃ contributes to the high activity and durability.

The template synthesis of ultrathin metallic Ir nanosheets as a robust electrocatalyst for acidic water splitting

Ultrathin metallic iridium nanosheets (∼4 nm) were synthesized using MIL-88A as the sacrificing template at room temperature. Ir-NS shows superior and stable water splitting performance in an acidic medium.