Efficient O-O Coupling at Catalytic Interface to Assist Kinetics Optimization on Concerted and Sequential Proton-Electron Transfer for Water Oxidation

Boosting Reaction Kinetics and Stability of Electrocatalytic Oxygen Evolution with Ir/CoV-LDH/Graphene Heterogeneous Electrocatalyst

To address the challenge of low catalytic performance in the electrocatalytic oxygen evolution reaction (OER) caused by slow reaction kinetics, a novel approach is developed utilizing the crystalline properties of iridium (Ir) and hydrogen-related layered double hydroxide (LDH) to enhance corrosion resistance. These materials are integrated into a CoV-LDH structure to design an Ir/CoV-LDH/G heterogeneous electrocatalyst. This innovative heterogeneous structure not only enhances the reaction kinetics but also optimizes the electronic structure of the catalyst through interactions at the heterogeneous interface, leading to excellent electrocatalytic OER performance. Notably, the Ir/CoV-LDH/G catalyst requires overpotentials of merely 203 and 289 mV to achieve current densities of 10 and 100 mA cm-2, respectively. Furthermore, when utilized in an Ir/CoV-LDH/G||Pt/C electrolytic cell for overall water splitting, it delivers a current density of 10 mA·cm-2 at a cell voltage of only 1.46 V, surpassing the performance of most commercial IrO₂||Pt/C and previously reported Ir-based and LDH electrocatalysts. The catalyst also exhibits remarkable stability, maintaining a current density of 100 mA·cm-2 for 100 h without significant degradation.

Rapid Microwave-Driven Sulfur Sublimation Synthesis of MS2/RuS2 (M = Fe, Co, Ni) for Efficient Alkaline Overall Water Splitting

Facing the complex application environment and overall inefficiency in the complete water-splitting process, the development of highly efficient and stable catalytic materials is urgently required. This study innovatively proposes and for the first time implements a rapid synthesis technique driven by microwave-induced sulfur sublimation, successfully preparing MS2/RuS2 (M = Co, Fe, Ni) heterostructure interfaces with high structural stability and uniform active site distribution within merely 60 s. By incorporating iron-group sulfides, the electronic structure of pyrite-type RuS2 is effectively modulated, enabling the developed MS2/RuS2@G catalyst to exhibit superior activity in alkaline environments. Particularly, the cobalt-based sulfide regulated pyrite-type RuS2 (CoS2/RuS2@G) achieves a mass activity in the hydrogen evolution reaction (HER) that is 15.4 times that of 20 wt.% Pt/C, and in the oxygen evolution reaction (OER), it surpasses commercial IrO2 by two orders of magnitude. This research not only provides a new pathway for enhancing the performance and environmental adaptability of water-splitting catalysts but also presents a simple and universal method to boost catalytic activity through a synergistic modulation strategy.

Spin Magnetic Effect Activate Dual Site Intramolecular O─O Bridging for Nickel-Iron Hydroxide Enhanced Oxygen Evolution Catalysis

The oxygen evolution reaction (OER) involves the recombination of diamagnetic hydroxyl (OH) or water (H2O) into the paramagnetic triplet state of oxygen (O2). The spin conservation of oxygen intermediates plays a crucial role in OER, however, research on spin dynamics during the catalytic process remains in its early stages. Herein, β-Ni(OH)2 and Fe-doped β-Ni(OH)2 (Ni5Fe1(OH)2) are utilized as model catalysts to understand the mechanism of spin magnetic effects at iron (III) sites during OER. Combined with magnetic characterization, it is founded that the introduction of Fe transforms the antiferromagnetic Ni(OH)2 into a ferromagnetic material. Testing the magnetic response of the catalyst under an external magnetic field, the OER activity of Ni5Fe1(OH)2 is significantly enhanced in comparison to Ni(OH)2. This improvement is likely due to the introduction of iron sites, which promote spin magnetic effects and enhance reaction kinetics, thereby increasing catalytic efficiency. Combining experimental and theoretical characterization, it is discovered that the iron sites accelerate the formation of heterogeneous dual-site O─O bridging, represented as ─Ni─O─O─Fe─, thereby effectively enhancing the kinetics of the OER reaction. This study provides a magnetic perspective on the structure-function relationship of magnetic iron-based catalysts and has significant implications for the design of new catalysts.

Complementary Multisite Turnover Catalysis toward Superefficient Bifunctional Seawater Splitting at Ampere-Level Current Density

The utilization of seawater for hydrogen production via water splitting is increasingly recognized as a promising avenue for the future. The key dilemma for seawater electrolysis is the incompatibility of superior hydrogen- and oxygen-evolving activities at ampere-scale current densities for both cathodic and anodic catalysts, thus leading to large electric power consumption of overall seawater splitting. Here, in situ construction of Fe4N/Co3N/MoO2 heterostructure arrays anchoring on metallic nickel nitride surface with multilevel collaborative catalytic interfaces and abundant multifunctional metal sites is reported, which serves as a robust bifunctional catalyst for alkaline freshwater/seawater splitting at ampere-level current density. Operando Raman and X-ray photoelectron spectroscopic studies combined with density functional theory calculations corroborate that Mo and Co/Fe sites situated on the Fe4N/Co3N/MoO2 multilevel interfaces optimize the reaction pathway and coordination environment to enhance water adsorption/dissociation, hydrogen adsorption, and oxygen-containing intermediate adsorption, thus cooperatively expediting hydrogen/oxygen evolution reactions in base. Inspiringly, this electrocatalyst can substantially ameliorate overall freshwater/seawater splitting at 1000 mA cm-2 with low cell voltages of 1.65/1.69 V, along with superb long-term stability at 500-1500 mA cm-2 for over 200 h, outperforming nearly all the ever-reported non-noble electrocatalysts for freshwater/seawater electrolysis. This work offers a viable approach to design high-performance bifunctional catalysts for seawater splitting.

Strengthening the Synergy between Oxygen Vacancies in Electrocatalysts for Efficient Glycerol Electrooxidation

Defect-engineered bimetallic oxides exhibit high potential for the electrolysis of small organic molecules. However, the ambiguity in the relationship between the defect density and electrocatalytic performance makes it challenging to control the final products of multi-step multi-electron reactions in such electrocatalytic systems. In this study, controllable kinetics reduction is used to maximize the oxygen vacancy density of a Cu─Co oxide nanosheet (CuCo2O4 NS), which is used to catalyze the glycerol electrooxidation reaction (GOR). The CuCo2O4-x NS with the highest oxygen-vacancy density (CuCo2O4-x-2) oxidizes C3 molecules to C1 molecules with selectivity of almost 100% and a Faradaic efficiency of ≈99%, showing the best oxidation performance among all the modified catalysts. Systems with multiple oxygen vacancies in close proximity to each other synergistically facilitate the cleavage of C─C bonds. Density functional theory calculations confirm the ability of closely spaced oxygen vacancies to facilitate charge transfer between the catalyst and several key glycolic-acid (GCA) intermediates of the GOR process, thereby facilitating the decomposition of C2 intermediates to C1 molecules. This study reveals qualitatively in tuning the density of oxygen vacancies for altering the reaction pathway of GOR by the synergistic effects of spatial proximity of high-density oxygen vacancies.

Recent progress in hierarchical nanostructures for Ni-based industrial-level OER catalysts

Exploring efficient and low-cost oxygen evolution reaction (OER) electrocatalysts reaching the industrial level current density is crucial for hydrogen production via water electrolysis. In this feature article, we summarize the recent progress in hierarchical nanostructures for the industrial-level OER. The contents mainly concern (i) the design of a hierarchical structure; (ii) a Ni-based hierarchical structure for the industrial current density OER; and (iii) the surface reconstruction of the hierarchical structure during the OER process. The work provides valuable guidance and insights for the manufacture of hierarchical nanomaterials and devices for industrial applications.