Anion-tuning of cobalt-based chalcogenides for efficient oxygen evolution in weakly alkaline seawater.

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]