Engineering Ni(OH)x/(Ni, Cu)Se2 heterostructure nanosheet arrays for highly-efficient water oxidation

The development of efficient and inexpensive alkaline oxygen evolution reaction (OER) catalysts is crucial for electrochemical water splitting. Cu-doped NiSe ₂ has good electrical conductivity and OER activity, but (Ni, Cu)Se ₂ will dissolve a large amount of Se during the OER process and adsorb on the surface of the catalyst in the form of selenite, which seriously affects its OER stability. Here, heterostructure electrocatalysts composed of crystalline (Ni, Cu)Se ₂ and amorphous Ni(OH) _x are designed. The Ni(OH) _x/(Ni, Cu)Se ₂ exhibits an distinguished catalytic performance for OER, needing only an overpotential of 200 mV at the current density of 10 mA cm ⁻² with a Tafel slope of 62 mV dec ⁻¹ in 1 M KOH. Combining the experimental and theoretical results, electronic interactions at the coupled interface optimize the free energy of the oxygen-containing intermediate and weaken the Ni-*O bond, which leads to enhanced OER activity and stability. This work of amorphous core-shell interface engineering to improve OER activity and stability may provide a strategy for the rational design of advanced non-precious metal electrocatalysts.