Fe doping and oxygen vacancy modulated Fe-Ni5P4/NiFeOH nanosheets as bifunctional electrocatalysts for efficient overall water splitting

[Display omitted] •A novel “semi-enclosed” phosphorization strategy is proposed to synthesize Fe-Ni5P4/NiFeOH porous nanosheets.•The doping and vacancy double control strategy for the design of bifunctional HER/OER catalysts is firstly demonstrated.•Fe doping and oxygen vacancy can optimize binding strength of intermediates by regulating electronic structure.•Fe-Ni5P4/NiFeOH-350 shows low overpotentials of ∼197 and ∼221 mV at 10 mA/cm2 for HER and OER, respectively. The efficient bifunctional catalysts for hydrogen and oxygen evolution reactions (HER/OER) have attracted great interest for hydrogen production from water splitting. Herein, the doping and vacancy double control strategy for the design of bifunctional catalysts is firstly demonstrated for the significant enhancement of HER/OER catalytic performances by constructing Fe doped-Ni5P4/Fe-doped Ni(OH)2 (Fe-Ni5P4/NiFeOH) hybrid nanosheets with rich oxygen vacancies. The experimental studies and first-principle calculations both prove that the combined effects of Fe doping and oxygen vacancy can easily regulate the electronic structure and accordingly optimize the adsorptions/desorptions of intermediates. The bifunctional Fe-Ni5P4/NiFeOH-350 shows small overpotentials of 197 and 221 mV for HER and OER, respectively, along with a low cell voltage of 1.55 V at 10 mA cm−2 and excellent long-term stability for water splitting.