Intercalating MnO2 Nanosheets With Transition Metal Cations to Enhance Oxygen Evolution

Abstract

AbstractThe catalytic activity of MnO2 nanosheets towards oxygen evolution depends highly on their interlayer environment. We present a systematic investigation on fine‐tuning of the interlayer environment of MnO2 nanosheets by intercalation through a facile cation exchange with inexpensive first‐row transition metal cations, including Ni2+, Co2+, Cu2+, Zn2+, and Fe3+ ions. Among them, the Ni‐intercalated MnO2 nanosheets show remarkably enhanced OER activity and long‐term stability, compared to pristine MnO2 nanosheets. The overpotential of 330 mV at a current density of 10 mA cm−2 is observed for the Ni‐intercalated MnO2 nanosheets. The ehancement mechanism of OER is studied by comparing physiochemical properties, such as the oxidation state of Mn, the interlayer distance, the increase in the disorder/twisting of MnO6 octahedra, and the interlayer cooperative binding of water molecules. The Ni intercalation, different from other metal cations, strengthens the Mn−O bond perpendicularly to the layer chains to facilitate the interlayer catalysis possibly between two Mn sites, and thus promotes the efficiency of oxygen evolution.