NiSe@Ni1−xFexSe2 Core–Shell Nanostructures as a Bifunctional Water Splitting Electrocatalyst in Alkaline Media

Herein a facile synthesis methodology is reported that results in a unique 3D NiSe@Ni1−xFexSe2 core–shell nanostructure on nickel foam substrate, where Ni1−xFexSe2 nanosheets are fabricated on NiSe nanowires through an iron‐doping‐induced phase transformation process under solvothermal conditions. This material demonstrates stable hydrogen and oxygen evolution activity in 1.0 m KOH with a small overpotential of 153 mV@−10 mA cm−2 and 236 mV@100 mA cm−2, respectively. Furthermore, an efficient and stable water electrolyzer with NiSe@Ni1−xFexSe2/nickel foam as both anode and cathode is fabricated, which requires a low overpotential of 1.60 V to deliver a current density of 10 mA cm−2. Such ion‐doping‐induced phase transformation paves a new way for fabricating highly efficient electrocatalysts for energy storage and conversion. Facile solvothermal iron doping in millerite‐type NiSe nanowires, embedded on nickel foam substrate, transforms the original phase to a NiSe@Ni1−xFexSe2 core–shell architecture. This structure allows performing stable hydrogen and oxygen evolution reaction in 1.0 m KOH with a small overpotential of 153 mV@−10 mA cm−2 and 236 mV@100 mA cm−2, therefore exhibiting 1.60 V@10 mA cm−2 as a stable water electrolyzer.