Transition metal dichalcogenides have been widely studied as active electrocatalysts for hydrogen evolution reactions. However, their properties as oxygen evolution reaction catalysts have not been fully explored. In this study, we systematically investigate a family of transition metal dichalcogenides (MX, M = Co, Ni, Fe; X = S, Se, Te) as candidates for water oxidation. It reveals that the transition metal dichalcogenides are easily oxidized in strong alkaline media via an in situ electrochemical oxidation process, producing nanoporous transition metal oxides toward much enhanced water oxidation activity due to their increased surface area and more exposed electroactive sites. The optimal cobalt nickel iron oxides that derived from their sulfides and selenides demonstrate a low overpotential of 232 mV at current density of 10 mA cm-2, a small Tafel slope of 35 mV per decade, and negligible degradation of electrochemical activity over 200 h of electrolysis. This study represents the discovery of nanoporous transition metal oxides deriving from their chalcogenides as outstanding electrocatalysts for water oxidation.
Keywords: electrocatalysts; in situ electrochemical tuning; nanoporous metal oxides; oxygen evolution reaction; transition metal chalcogenides.