Electrochemical water splitting has attracted great attention for hydrogen production, yet is still limited by capable electrocatalysts. Herein, the ultrathin porous nickel–cobalt phosphide nanosheets (NiCoP NS) are successfully synthesized by microwave‐assisted technique and used as a robust bifunctional catalyst for overall water splitting. The NiCoP NSs can show excellent catalytic activity with a low overpotential (η10) of 105 mV at 10 mA cm−2 for hydrogen evolution reaction and a small overpotential (η10) of 240 mV at 10 mA cm−2 for oxygen evolution reaction. The water splitting device of NiCoP NSs can give lower cell voltage of 1.45 and 1.67 V at a current density of 10 and 100 mA cm−2. The better electrochemical performance should be attributed to the synergetic effect of nickel and cobalt, porous morphology, and large surface area. These key factors boost the reactant's adsorption energy, number of exposed active sites, and produce different channels for charge transfer and reactant/electrolyte diffusion.

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