Electrochemical etching induced high-valence cobalt with defects site for boosting electrochemical water splitting

The active origin of the high-valence-state enhance the oxygen evolution reaction performance, which still lacks confident evidence, especially on how to delay the loss of activity by retaining the valence dynamically stable. Herein, to demonstrate the role of pure electrochemistry on the evolution process is first detailed explored. The electrochemical operation is found benignly for building the high-valence cobalt (Co) on the surface and enhancing the degree of the weakened-crystalline structure due to the selenium (Se) leaching. The anodized CoSe2 (A-CoSe2) with the above structures was mainly linked to high intrinsic activity (η = 254 mV@10 mA cm−2) and durability (120 h), as well as a high-current (0.5 A cm−2, 30 h), withstand performance in anion exchange membrane (AEM) water electrolyzer among best Co-based catalysts. The high durability unravels the increasingly weakly crystalline structure was benign for the dynamical retainment of the metallic Co-defect structure and high-valence active sites.