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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. [ABSTRACT FROM AUTHOR]

Producing hydrogen via water electrolysis could be a favorable technique for energy conversion, but the freshwater shortage would inevitably limit the industrial application of the electrolyzers. Being an inexhaustible resource of water on our planet, seawater can be a promising alternative electrolyte for industrial hydrogen production. However, many challenges are hindering the actual application of seawater splitting, especially the competing reactions relating to chlorine at the anode that could severely corrode the catalysts. The execution of direct seawater electrolysis needs efficient and robust electrocatalysts that can prevent the interference of competing reactions and resist different impurities. In recent years, researchers have made great advances in developing high-efficiency electrocatalysts with improved activity and stability. This review will provide the macroscopic understanding of direct seawater splitting, the strategies for rational electrocatalyst design, and the development prospects of hydrogen production via seawater splitting. The nonprecious metal-based electrocatalysts for stable seawater splitting and their catalytic mechanisms are emphasized to offer guidance for designing the efficient and robust electrocatalyst, so as to promote the production of green hydrogen via seawater splitting. [ABSTRACT FROM AUTHOR]

The effects of anion-tuning on cobalt-based chalcogenides for OER in weakly alkaline seawater are comprehensively investigated via DFT, XAS, and XPS, and S substitution is proven to optimize the electronic structure of active site to prevent Cl* from transforming to ClO- for anti-corrosion. Co 3 S 4 could stably operate at the high current density of 100 mA cm−2 for 100h without any performance degradation. [Display omitted] • Co 3 S 4 and Co 3 Se 4 were transformed from the Co 3 O 4 precursor by hydrothermal method. • DFT predicts the possible active sites and mechanisms of OER and HCER in seawater. • S and Se substitution increases energy barrier of Cl* to ClO- for anti-corrosion. • S and Se could promote Co site transforming to active phase. • Co 3 S 4 stably operates at OER current density of 100 mA cm−2 in weakly alkaline seawater for 100 h and netrual seawater for 20 h. Regulating the electronic structure is of great importance for improving the performance, stability, and selectivity of seawater splitting catalysts. Herein, cobalt-based oxide and chalcogenide (Co 3 X 4 , X = O, S, and Se) are synthesized to investigate the effect of anions on the electronic structure, catalytic performance and selectivity of the seawater oxidation catalysts. The theoretical calculations predict the possible active sites of oxygen evolution reaction and hypochlorite evolution reaction. Then the experimental characterization and calculation results demonstrate that S and Se substitution could regulate the electronic structure and d-band center of Co site, enhance the metallicity of catalysts. Moreover, the energy barrier of Cl* conversion to ClO- could be modulated for preventing the formation of ClO- by anions regulating. Consequently, Co 3 S 4 could stably operate at a current density of 100 mA cm−2 in 0.1 M KOH + 0.6 M NaCl for 100 h and in neutral seawater for 20 h. [ABSTRACT FROM AUTHOR]