Achieving highly efficient electrocatalytic oxygen evolution with ultrathin 2D Fe-doped nickel thiophosphate nanosheets

Exploring earth-abundant electrocatalysts to realize efficient oxygen evolution reaction (OER) is highly desired for developing sustainable electrochemical energy storage and conversion technologies. Herein, ultrathin single-crystalline Fe-doped nickel thiophosphate (NiPS₃) nanosheets prepared in large scale by an easy solid-state method were demonstrated to be highly efficient OER electrocatalysts. The density functional theory (DFT) calculations reveal that the Fe-doping effectively decreases the energy barrier of OER path by reducing the binding of the oxygen-containing species on the surface of NiPS₃. As such, the Fe-doped NiPS₃ nanosheets show a low overpotential of 256 mV to reach a current density of 30 mA cm⁻² and a small Tafel slope of 46 mV dec⁻¹. To our knowledge, this is one of the best OER electrocatalysts in alkaline medium to date. The in-depth mechanism study demonstrates that the in-situ formed Fe-doped nickel oxides/hydroxides shell, resulting from the surface oxidation during the OER process, not only may serve as favorable electrocatalytic species but also improves the chemical stability of the Fe-doped NiPS₃ in alkaline electrolyte. This work provides a new perspective for designing highly efficient OER electrocatalysts based on the ternary two-dimensional layered metal thiophosphates.