Electrodeposited of ultrathin VOx-doped NiFe layer on porous NiCo phosphide for efficient overall water splitting

An ultrathin VOx-doped NiFe alloy layer (VOx@NiFe) was electrodeposited on the surface of nickel-cobalt phosphide (NiCoP) supported by titanium mesh (TM) to achieve a highly active and low-cost bifunctional electrocatalyst for overall water splitting. VOx doping not only significantly enhances the electrochemical surface areas and the concentration of oxygen vacancies in the NiFe/NiCoP/TM composite, but also greatly improves the surface hydrophilicity. The VOx@NiFe/NiCoP/TM electrode retains a 3D porous structure of NiCoP/TM and exhibits superior electrocatalytic activity for water electrolysis. It requires the overpotentials of merely 45 and 215 mV to deliver the current density of 10 mA cm−2 in 1.0 M KOH for HER and OER, respectively. Meanwhile, the VOx@NiFe/NiCoP/TM electrode also displays robustness and outstanding durability in alkaline medium. Serving as both anode and cathode electrocatalysts in a two-electrode water electrolytic cell, the bifunctional VOx@NiFe/NiCoP/TM electrodes only require a potential of 1.52 and 1.65 V to deliver the current densities of 10 and 50 mA cm−2 with excellent durability. This work provides a design of multilevel porous structure of bifunctional electrocatalysts for energy storage and conversion.