Fe-Doped Ni–Co Phosphide Nanoplates with Planar Defects as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Highly efficient and low-cost bifunctional electrocatalysts in the same medium are indispensable for overall water splitting. Herein, Fe-doped Ni–Co phosphide nanoplates with a hierarchical nanostructure were successfully fabricated on a carbon cloth (Fex-NiCoP) via a facile method with electrodesposition and PH3 plasma treatment. Benefiting from the hierarchical structure, two-dimensional nanoplates comprising fine nanocrystals and doping effects of Fe, the Fex-NiCoP demonstrates excellent electrocatalytic performance for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which is sensitive to the Fe content. By controlling the Fe content, Fe1-NiCoP achieves 10 mA cm–2 at a low overpotential of 60 mV for the HER, while Fe2-NiCoP with a higher Fe doping content drives 50 mA cm–2 at only 293 mV for the OER. Upon high-resolution transmission electron microscopy, some planar defects were observed in the Fe-doped NiCoP nanocrystals, which may account for the increased exposure of active sites. When the optimal Fex-NiCoP electrodes were employed as the anode and cathode for water electrolysis in the alkaline electrolyte, the electrolyzer achieves 10 mA cm–2 at a low cell voltage of 1.61 V. Our work might shed light on rational design of the efficient multimetallic phosphide bifunctional electrocatalysts for overall water splitting.