Robust Oxygen Evolution Reaction Electrocatalysts Research Articles

Metallic Ru─Ru Interaction in Ruthenium Oxide Enabling Durable Proton Exchange Membrane Water Electrolysis.

Developing efficient and robust electrocatalysts toward the oxygen evolution reaction (OER) is critical for proton exchange membrane water electrolysis (PEMWE). RuO2 possesses intrinsically high OER activity, but the concurrent electrochemical dissolution leads to rapid deactivation. Here a unique RuO2 catalyst containing metallic Ru─Ru interactions (m-RuO2) is reported, which maintains stability in practical PEMWE for 100h at 60 °C and 1 A cm-2. Experimental and theoretical investigations suggest that the presence of Ru─Ru interactions significantly increases the energy barrier for the formation of RuO2(OH)2, which is a key intermediate for Ru dissolution, and hence substantially mitigates the electrochemical corrosion of m-RuO2. Meanwhile, the Ru4d band center downshifts, accordingly, ensuring the high OER activity, and the participation of lattice oxygen in the OER is also suppressed at the Ru─Ru sites, further contributing to the enhanced durability. Interestingly, such enhanced stability is also dependent on the size of metallic Ru─Ru cluster, where the energy barrier is further increased for Ru3, but is decreased for Ru5. These results highlight the significance of local coordination structure modulation on the electrochemical stability of RuO2 and open a feasible avenue toward the development of robust OER electrocatalysts for high-performance PEMWE.

Reduced valence state of iridium supported on antimony doped tin oxide as a highly active and robust oxygen evolution reaction electrocatalyst for proton exchange membrane-based electrolysis

We use facile microwaves (MWs)-assisted polyol method to synthesize metallic Ir-nanoparticles (Ir-NPs) supported on antimony-doped tin oxide (ATO). Parameters such as Ir loading, reaction temperature and reaction time were optimized to achieve high electrocatalytic performance of oxygen evolution reaction (OER) activity and durability under the corrosive OER environment of acidic electrolyzers. Electrocatalysts with varying Ir loading between 10 and 40 wt% were synthesized at two different temperatures (140 °C and 160 °C) to compare morphology, Ir valence state, OER activity and stability. This analysis has revealed efficient electrocatalyst synthesis with a narrow size distribution and homogeneous dispersion over the support surface. An electron rich state of Ir, contributing to the electrocatalyst activity and stability, was achieved at the synthesis temperature of 160 °C. Among the as-synthesized electrocatalysts, one, named Ir/ATO.AT-40-160, has demonstrated high activity (449 ± 2.7 A gIr−1) and high AST stability (75.1% retained current), reaching respectively 1.5 and 2 times those of a state-of-the-art commercial electrocatalyst. The high catalytic activity and excellent stability can both be attributed to the depressed overoxidation of the active Ir due to the low valence state, appropriate composition, and highly dispersed Ir NPs over the support surface.

ZIF-8@ZIF-67 derived Fe–CoS2/CNT carbon polyhedron for enhanced electrocatalytic oxygen evolution reaction

In the pursuit of highly active electrocatalysts is crucial to overcome the sluggish kinetics of oxygen evolution reaction (OER). Herein, Fe–CoS2/carbon nanotubes anchored on carbon polyhedron (Fe–CoS2/CNT CPs) is prepared by using zeolitic imidazolate framework-8@zeolitic imidazolate framework-67 (ZIF-8@ZIF-67) as template. A series of analysis demonstrates the incorporation of Fe via wrapped Fe-EDTA can exert charge transfer between Co and Fe and optimize the adsorption of targeted intermediates, which favors for enhanced OER performance. Moreover, the catalytic effect of Co and Fe not only promotes the growth of carbon nanotubes but also enhances the degree of graphitization. The carbon skeletons embedded with carbon nanotubes derived from ZIF-8@ZIF-67 offer high specific surface area and strengthen the electrical conductivity of Fe–CoS2/CNT CPs. Therefore, compared with its counterpart and commercial RuO2, the designed Fe–CoS2/CNT CPs with regulated electronic structure displays the lowest overpotential of 293 mV at the current density of 10 mA cm−2 in 1.0 M KOH solution for OER. This work explores a facile strategy for manipulate electronic structure and electrical conductivity of metal-organic frameworks derived catalysts simultaneously for robust OER electrocatalysts.

The role of aluminium in metal–organic frameworks derived carbon doped with cobalt in electrocatalytic oxygen evolution reaction

Water electrolysis is one of the most crucial processes in the development of new energy sources, where ultra-clean fuel is produced - hydrogen. Oxygen evolution reaction (OER) is the sluggish process of overall water splitting. Therefore, this study presents the design, characterization and electrochemical study of cobalt-based electrocatalysts embedded into porous carbons derived from an Al-metal–organic framework (MOF). The key aspects to be revealed were carbonization temperature and aluminium impact on the composite electrochemical performance. It was found that aluminium presence boosts the OER performance of the anode via lowering electrolyte resistance, reaching an overpotential of 380 mV at the current density of 10 mA/cm−2, which is improved by 80 mV compared to the composite without aluminium. Similar effect was present in EIS measurement, where the electrocatalyst functionalized with cobalt in the presence of aluminium showed the lowest resistances, 0.89 Ω and 2.82 Ω for R1 and R2. This is due to the formation of additional electrocatalytically active species in the form of Al-Co alloy what was clearly proved by the XPS study. It shows that cobalt favoured aluminium to act simultaneously as active sites accelerating the efficiency of the OER process. Additionally, carbon played the role of a booster of the OER activity of cobalt with sustained high durability during cycling. Therefore, a facile procedure to tune the structure of carbon-based structures derived from Al-based metal–organic frameworks is proposed and the resulting cobalt/aluminium modification serves as a robust electrocatalyst for OER.

Noble‐Metal‐Free Oxygen Evolution Reaction Electrocatalysts Working at High Current Densities over 1000 mA cm−2: From Fundamental Understanding to Design Principles

Alkaline water electrolysis provides a promising route for “green hydrogen” generation, where anodic oxygen evolution reaction (OER) plays a crucial role in coupling with cathodic hydrogen evolution reaction. To date, the development of highly active and durable OER catalysts based on earth‐abundant elements has drawn wide attention; nevertheless, their performance under high current densities (HCDs ≥1000 mA cm−2) has been less emphasized. This situation has seriously impeded large‐scale electrolysis industrialization. In this review, in order to provide a guideline for designing high‐performance OER electrocatalysts, the effects of HCD on catalytic performance involving electron transfer, mass transfer, and physical/chemical stability are summarized. Furthermore, the design principles were pointed out for obtaining efficient and robust OER electrocatalysts in light of recent progress of OER electrocatalysts working above 1000 mA cm−2. These include the aspects of developing self‐supported catalytic electrodes, enhancing intrinsic activity, enhancing the catalyst–support interaction, engineering surface wettability, and introducing protective layer. Finally, summaries and outlooks in achieving OER at industrially relevant HCDs are proposed.

Rationally Reconstructed Metal-Organic Frameworks as Robust Oxygen Evolution Electrocatalysts.

Reconstructing metal-organic framework (MOFs) toward a designed framework structure provides breakthrough opportunities to achieve unprecedented oxygen evolution reaction (OER) electrocatalytic performance, but has rarely, if ever, been proposed and investigated yet. Here, the first successful fabrication of a robust OER electrocatalyst by precision reconstruction of an MOF structure is reported, viz., from MOF-74-Fe to MIL-53(Fe)-2OH with different coordination environments at the active sites. Due to the radically reduced eg -t2g crystal-field splitting in Fe-3d and the much suppressed electron-hopping barriers through the synergistic effects of the O species the efficient OER of in MIL-53(Fe)-2OH is guaranteed. Benefiting from this desired electronic structure, the designed MIL-53(Fe)-2OH catalyst exhibits high intrinsic OER activity, including a low overpotential of 215 mV at 10 mA cm-2 , low Tafel slope of 45.4 mV dec-1 and high turnover frequency (TOF) of 1.44 s-1 at 300 mV overpotential, over 80 times that of the commercial IrO2 catalyst (0.0177 s-1 ).Consistent with the density functional theory (DFT) calculations, the real-time kinetic simulation reveals that the conversion from O* to OOH* is the rate-determining step on the active sites of MIL-53(Fe)-2OH.

Ultra-low palladium engineered nickel sulfide heterostructure supported on 3D nickel foam as a highly efficient and stable electrocatalyst for water oxidation

• 0.1PdNiS/NF requires only 275 mV overpotential to achieve a current density of 10 mAcm -2 , which is less than NiS/NF (385 mV) and commercial RuO 2 /NF (370 mV). • The Tafel slope of 0.1PdNiS/NF (65 mVdec -1 ) is lower than NiS/NF (132 mVdec -1 ) and commercial RuO 2 /NF. • 0.1PdNiS/NF demonstrated exceptional durability for approximately 14 hours at 10 mAcm -2 . • TOF of 0.1PdNiS was calculated to be 1.31 s -1 at an overpotential of 320 mV, which is greater than the NiS/NF (0.5 s -1 ). Electrochemical water splitting (EWS) has been a crucial process in the production of green fuels (oxygen and hydrogen) for a sustainable energy economy. One of the key processes in the EWS is water oxidation or the oxygen evolution reaction (OER). It is highly desirable to create cost-effective, efficient, and robust electrocatalysts for OER. Here, we present ultra-low Pd doped NiS-NiS 2 heterostructure on NF (0.1PdNiS/NF) grown in-situ by acid etching followed by a simple hydrothermal sulfurization method for excellent OER electrocatalytic activity in alkaline media. Interestingly, low overpotential of 275 mV is required for the 0.1PdNiS/NF to achieve a current density of 10 mAcm -2 , which is less than both NiS/NF (385 mV) and commercial RuO 2 /NF (370 mV). Because of the strong electronic interaction between Pd and NiS, 0.1PdNiS/NF has a small Tafel slope of 65 mV/dec and has shown excellent durability for approximately 14h. Therefore, the findings described above provide significant insights in the design of high-performance OER catalysts with ultra-low precious metal loading.

Surface-neutralization engineered NiCo-LDH/phosphate hetero-sheets toward robust oxygen evolution reaction

Developing highly active oxygen evolution reaction (OER) electrocatalysts with robust durability is essential in producing high-purity hydrogen through water electrolysis. Layered double hydroxide (LDH) based catalysts have demonstrated efficient catalytic performance toward the relatively sluggish OER. By considering the promotion effect of phosphate (Pi) on proton transfer, herein, a facile phosphate acid (PA) surface-neutralization strategy is developed to in-situ construct NiCo-LDH/NiCoPi hetero-sheets toward OER catalysis. OER activity of NiCo-LDH is significantly boosted due to the proton promotion effect and the electronic modulation effect of NiCoPi. As a result, the facilely prepared NiCo-LDH/NiCoPi catalyst displays superior OER catalytic activity with a low overpotential of 300 mV to deliver 100 mA cm−2 OER and a Tafel slope of 73 mV dec−1. Furthermore, no visible activity decay is detected after a 200-h continuous OER operation. The present work, therefore, provides a promising strategy to exploit robust OER electrocatalysts for commercial water electrolysers.

Constructing Ag modified NiCoSe2 hybrid nanosheet on 3D-nickel foam as a robust oxygen evolution reaction electrocatalyst

Transition metal selenides are promising oxygen evolution reaction (OER) catalysts, and element doping is a strategy to further enhance their catalytic performance. However, the choice of doping elements and methods needs further study. In this work for cobalt selenide, Ni is has been selected for isomorphic doping to NiCoSe2 with silver doped in bulk to obtain Ag–NiCoSe2 nanosheet on NF. The addition of nickel can form a eutectic phase with cobalt to obtain an effective synergistic catalytic effect. The addition of Ag can regulate the adsorption energy of the active site and conductivity. The as-prepared Ag–NiCoSe2/NF has good catalytic performance for OER, and a current density of 100 mA cm−2 can be achieved with only 270 mV. Its catalytic ability is far superior to that of non-Ag-doped NiCoSe2, which is due to the fact that the sheet structure provides more active sites, and the metal doping modulates the electronic configuration, which effectively improves the intrinsic activity. Moreover, Ag–NiCoSe2/NF can maintain a long-term high-efficiency catalytic process for more than 20 h at a current density of 100 mA cm−2. Therefore, this work proves that metal doping is of great significance for improving the catalytic activity of transition metal selenides.

Multiscale Engineering of Nonprecious Metal Electrocatalyst for Realizing Ultrastable Seawater Splitting in Weakly Alkaline Solution.

Seawater electrolysis is an attractive technique for mass production of high‐purity hydrogen considering the abundance of seawater. Nevertheless, due to the complexity of seawater environment, efficient anode catalyst, that should be, cost effective, highly active for oxygen evolution reaction (OER) but negligible for Cl2/ClO– formation, and robust toward chlorine corrosion, is urgently demanded for large‐scale application. Although catalysis typically appears at surface, while the bulk properties and morphology structure also have a significant impact on the performance, thus requiring a systematic optimization. Herein, a multiscale engineering approach toward the development of cost‐effective and robust OER electrocatalyst for operation in seawater is reported. Specifically, the engineering of hollow‐sphere structure can facilitate the removal of gas product, while atom‐level synergy between Co and Fe can promote Co sites transforming to active phase, and in situ transformation of sulfate ions layer protects catalysts from corrosion. As a result, the as‐developed hollow‐sphere structured CoFeSx electrocatalyst can stably operate at a high current density of 100 mA cm–2 in the alkaline simulated seawater (pH = 13) for 700 h and in a neutral seawater for 20 h without attenuation. It provides a new strategy for the development of electrocatalysts with a broader application potential.

Reprogramming thermodynamic-limiting oxidation cycle in NiFe-based oxygen evolution electrocatalyst through Mo doping induced surface reconstruction

Engineering of robust nonprecious electrocatalysts toward anodic oxygen evolution reaction (OER) is of great significance for lowering the cost and energy consumption for renewable fuel production. Herein, we report NiFeMoOx nanosheets as high-performance OER electrocatalyst through promoting the thermodynamic-limiting oxidation cycle process in NiFe oxyhydroxide via high-valence Mo doping. The NiFeMoOx nanosheets are prepared by an elaborate in-situ solvothermal etching-depositing process with NiFe alloy framework as substrate and metal precursors. The resultant nanosheets exhibit outstanding alkaline OER activity, requires only 235/282/327 mV overpotentials to achieve current density of 10/100/300 mA cm−2, respectively, with a good long-term stability at 20 mA cm−2 for 72 h. Besides, the Tafel slope low to 28.1 mV dec−1 indicates a favorable OER kinetics. The superior catalytic activity of NiFeMoOx nanosheets should be attributed to the lower oxidation states of Ni and Fe induced by high-valence dopant, leading to easier surface reconstruction at low charge oxidation cycling during OER, thereby effectively reducing the overpotential. The synergy between the electronic effect among multimetallic sites and the unique morphology is expected to inspire the development of robust OER electrocatalyst for industrial application.

CO induced phase-segregation to construct robust and efficient IrRux@Ir core-shell electrocatalyst towards acidic oxygen evolution

The development of highly active and durable electrocatalysts towards oxygen evolution reaction (OER) in acidic solution is essential for the commercialization of proton exchange membrane water electrolysis (PEMWE). Herein, we design a rational CO-induced phase-segregation strategy to efficient construction of core-shell structure electrocatalyst featured with IrRux core and Ir-rich shell (IrRux@Ir). X-ray photoelectron spectroscopy reveals that the intensive electronic interaction between IrRux core and Ir-rich shell induces the charge transfer from Ir to IrRux, thereby increasing the oxidation state of surface Ir sites and leading to an enhanced OER activity. Simultaneously, the Ir-rich shell efficiently protects the inner Ru atoms against dissolution during the long-term electrolysis, in turn significantly improving the structural stability. The resultant IrRux@Ir catalyst exhibits a low overpotential of ca. 288 mV at a current density of 10 mAcm−2 and desirable durability. Impressively, the membrane electrode assembly integrated with IrRux@Ir as anode maintains a steady value of approximately 1.83 ± 0.02 V during 400 h of electrolysis at a current density of 1 A cm−2, demonstrating that the IrRux@Ir is one of the most robust OER electrocatalyst to date. This study provides a new perspective to design high performance and robust OER electrocatalysts in PEMWE.

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

Hydrogen is a most desirable solar energy storage medium. It provides reliable, scalable, and long-term energy storage, while helping in the decarbonization of the energy cycle. Such a storage medium is required for further deployment of photovoltaics, either for their inclusion into transportation and heavy industries or for supporting renewable grid management. The most accessible hydrogen source is water. However, fresh water is a scarce resource, while seawater is abundant worldwide. A major drawback of seawater electrolysis comes from chloride oxidation competing with the oxygen evolution reaction (OER). This may produce toxic products such as chlorine and also limits the hydrogen energy efficiency of the overall process. Thus, selective catalysts toward the OER are of strong technological interest. Here we report the electrocatalytic activity of heterogeneous cobalt hexacyanoferrate toward seawater oxidation. Combining experimental and computational studies, we highlight the great difficulty in obtaining such selectivity and its main mechanistic descriptors. This Prussian blue derivative is an excellent and robust OER electrocatalyst, but unfortunately, it is not selective enough toward the OER in the presence of Cl– anions. Faradaic efficiencies above 30% toward Cl2 were observed during untreated seawater bulk electrolysis.

Theoretical and experimental exploration of tri-metallic organic frameworks (t-MOFs) for efficient electrocatalytic oxygen evolution reaction

High performance and cost-effective electrocatalysts are crucial to the oxygen evolution reaction (OER) in water splitting. Herein, we use density functional theory (DFT) calculation to systematically explore the catalytic activities of single-metallic organic frameworks (s-MOFs, such as Fe36C108O156), dual-metallic organic frameworks (d-MOFs, such as Fe26Co10C108O156, Fe30Ni6C108O156), and tri-metallic organic frameworks (t-MOFs, such as Fe26Ni2Co8C108O156) for electrocatalytic OER. The DFT calculation and experimental results suggest that the OER performance could be promoted with reduced activation energy barrier and accelerated kinetics by introducing Co and Ni into the unit cell of Material of Institute Lavioisier (MIL). The optimized t-MOFs exhibited an ultra-low overpotential of only 200 mV at the current density of 10 mA cm−2 and a small Tafel slope of 34 mV dec−1. This work proposes that the t-MOFs induced multi-metallic active sites and synergetic effect are promising strategies in designing highly efficient and robust OER electrocatalysts.

Hierarchical porous nickel supported NiFeOxHy nanosheets for efficient and robust oxygen evolution electrocatalyst under industrial condition

As an ideal clean energy carrier, hydrogen is regarded as the most promising alternative to replace fossil fuels in the future energy system. Compared to the traditional steam reforming process, water electrolysis is an innovative method for green hydrogen production. The oxygen evolution reaction (OER) with slow kinetics limits the efficiency of water electrolysis, thus, the fabrication of efficient and robust electrocatalysts for OER is highly desirable to promote the development of hydrogen industry. Herein, we developed a robust OER electrocatalyst by coupling NiFeOxHy nanosheets with porous nickel (PN) substrate via bubble template method. The NiFeOxHy-PN electrocatalyst displays superior electrocatalytic performance, the overpotential for OER at 100 mA cm−2 and 1000 mA cm−2 are 265 mV and 326 mV, respectively. Especially, the NiFeOxHy-PN exhibits better activity and durability than the commercial Raney nickel (RN) in alkaline water electrolysis under industrial conditions, which indicates its potential for industrial application. This work provides an efficient strategy to synthesize advanced electrocatalyst for alkaline water electrolysis.

Constructing Active Sites from Atomic-Scale Geometrical Engineering in Spinel Oxide Solid Solutions for Efficient and Robust Oxygen Evolution Reaction Electrocatalysts.

Spinel oxides are considered as promising low‐cost non‐precious metal electrocatalysts for oxygen evolution reaction (OER) due to their desirable catalytic activities and fast kinetics. However, as a result of the structural complexity of spinel oxides, systematic and in‐depth studies on enhancing the OER performance of spinel oxides remain inadequate. In particular, the construction of active sites regarding the large number of unoccupied octahedral interstices has not yet been explored. Herein, more octahedral sites with high OER activities are constructed on the surface of spinel oxides via a cationic misalignment, which is induced by the defects in the spinel oxide solutions, i.e., MoFe2O4 and CoFe2O4 nanosheets supported on an iron foam (MCFO NS/IF). With increased active sites and modified electronic structure, the state‐of‐the‐art electrocatalyst exhibits the excellent OER catalytic activity with an onset potential of 1.41 V versus RHE and an overpotential of 290 mV to achieve a current density of 500 mA cm−2. Moreover, such an electrocatalyst also demonstrates fast kinetics with the Tafel slope of 38 mV dec−1 and superior durability by maintaining the OER activity at 250 mA cm−2 for 1000 h.

Ultralow Ru doping induced interface engineering in MOF derived ruthenium-cobalt oxide hollow nanobox for efficient water oxidation electrocatalysis

• A MOF mediated method has been proposed for the synthesis of (Ru-Co)O x nanobox. • The (Ru-Co)O x nanoboxes are endowed with rich vacancies and interfaces. • The doping of ultralow Ru effectively modifies the electronic structure of CoO x . • (Ru-Co)O x nanoboxes could deliver outstanding electrocatalytic OER performance. For accelerating the reaction kinetics of oxygen evolution reaction (OER) and improving the efficiency of water electrolysis, it is essential to develop high-performance and robust OER electrocatalysts. Herein, heterostructured ruthenium-cobalt oxide hollow nanoboxes are developed for enabling a highly efficient OER electrocatalysis. Benefitting from the desirable structural and compositional merits of more exposure of surface active centers, modulated electronic structure, and interfacial synergy effect, the (Ru-Co)O x hollow nanobox could exhibit excellent electrocatalytic performance toward OER. Particularly, an extremely low overpotential of 265 mV is necessary for the optimized (Ru-Co)O x -350 to achieve a current density of 10 mA cm −2 , together with a small Tafel slope of 60 mV dec -1 . More interestingly, by combing (Ru-Co)O x -350 with Pt/C for driving alkaline water splitting, an ultralow cell voltage of merely 1.57 V is required.

Donor-Acceptor Couples of Metal and Metal Oxides with Enriched Ni3+ Active Sites for Oxygen Evolution.

Exploiting precious-metal-free and high-activity oxygen evolution reaction (OER) electrocatalysts has been in great demands toward many energy storage and conversion processes, for example, carbon dioxide reduction, metal-air batteries, and water splitting. In this study, the simple solid-state method is employed for coupling Ni (electron donors) with lower-Fermi-level MoO2 or WOx (electron acceptors) into donor-acceptor ensembles with well-designed interfaces as robust electrocatalysts for OER. The resulting Ni/MoO2 and Ni/WOx electrocatalysts exhibit smaller overpotentials of 287 and 333 mV at 10 mA cm-2 as well as smaller Tafel slopes of 51 and 65 mV/dec, respectively, with respect to the single Ni, MoO2, WOx, and even the benchmark RuO2 in 1 M KOH. Specially, on account of a higher Fermi level of Ni in comparison with MoO2 and WOx, their strong electronic interaction results in directional interfacial electron transfer and increases the hole density over Ni, dramatically enriching the population of high-valence Ni3+ active sites and decreasing the Fermi level of Ni. The existence of Ni3+ can strengthen the chemisorption of OH-, and the downshift of the Ni Fermi level can significantly expedite migration of electrons toward the surface of catalysts during OER, thus synergistically boosting the OER catalytic performance. Furthermore, the inner Ni/MoO2 and Ni/WOx heterostructures and the electrochemically induced surface layers of oxides/hydroxides collectively boost the OER kinetics. This study highlights the importance of designing highly efficient OER electrocatalysts with high-valence active species (Ni3+) and better matched energy levels induced by the work function difference through interfacial engineering.

Recent Development of Oxygen Evolution Electrocatalysts in Acidic Environment.

The proton exchange membrane (PEM) water electrolysis is one of the most promising hydrogen production techniques. The oxygen evolution reaction (OER) occurring at the anode dominates the overall efficiency. Developing active and robust electrocatalysts for OER in acid is a longstanding challenge for PEM water electrolyzers. Most catalysts show unsatisfied stability under strong acidic and oxidative conditions. Such a stability challenge also leads to difficulties for a better understanding of mechanisms. This review aims to provide the current progress on understanding of OER mechanisms in acid, analyze the promising strategies to enhance both activity and stability, and summarize the state-of-the-art catalysts for OER in acid. First, the prevailing OER mechanisms are reviewed to establish the physicochemical structure-activity relationships for guiding the design of highly efficient OER electrocatalysts in acid with stable performance. The reported approaches to improve the activity, from macroview to microview, are then discussed. To analyze the problem of instability, the key factors affecting catalyst stability are summarized and the surface reconstruction is discussed. Various noble-metal-based OER catalysts and the current progress of non-noble-metal-based catalysts are reviewed. Finally, the challenges and perspectives for the development of active and robust OER catalysts in acid are discussed.

Construction of echinoids-like MoS2@NiS2 electrocatalyst for efficient and robust water oxidation

Boosting stability, durability, and intrinsic activity of electrocatalysts are the world’s concerns in promoting the application of oxygen evolution reaction (OER). Ni is averagely required in efficient electrocatalysts for OER, while Mo is familiar to hydrogen evolution reaction (HER). Herein, we introduce Mo into electrocatalysts for OER and synthesize an echinoids-like MoS2@NiS2 electrocatalyst with unique morphology, which demonstrates rapid reaction kinetics and impressive catalysis activity. Furthermore, the electrocatalyst shows low overpotentials of 356 mV at 100 mA cm−2 as well as a Tafel slope of 82.6 mV dec−1 in alkaline media. Meanwhile, the electrocatalyst has a large double-layer capability (Cdl) and electrochemically active surface areas (ECSA) values. The OER performances remarkably enhanced with the help of MoS2 affiliation. Owning to the Ni compounds as the substrate, the catalyst can maintain a good stability in alkaline solution even after 10 h of chronoamperometry test at 1.51 V. Our study proposes a feasible way to obtain a high-efficient and robust OER electrocatalyst for the practical application.