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

Abstract

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 (Co3X4, 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, Co3S4 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.