Unveiling the Promotion of Surface‐Adsorbed Chalcogenate on the Electrocatalytic Oxygen Evolution Reaction

Transition metal chalcogenides (TMCs) are efficient oxygen evolution reaction (OER) pre-electrocatalysts, and will in situ transform into metal oxyhydroxides under OER condition. However, the role of chalcogen is not fully elucidated after oxidation and severe leaching. Here we present the vital promotion of surface-adsorbed chalcogenates on the OER activity. Taking NiSe 2 as an example, in situ Raman spectroscopy revealed the oxidation of Se-Se to selenites (SeO 3 2- ) then to selenates (SeO 4 2- ). Combining the severe Se leaching and the strong signal of selenates, it is assumed that the selenates are rich on the surface and play significant roles. As expected, adding selenites to the electrolyte of Ni(OH) 2 dramatically enhance the OER activity. And sulfates also exhibit the similar effect, suggesting the promotion of surface-adsorbed chalcogenates on OER is universal. Our findings offer unique insight into the transformation mechanism of materials during electrolysis.