NiMo/NiCo2O4 as synergy catalyst supported on nickel foam for efficient overall water splitting

It is highly desirable to develop efficient and low-cost bifunctional HER/OER electrocatalysts for overall water splitting. Herein, Ni5Mo/NiCo2O4 heterojunctions loaded on nickel foam were prepared. The catalyst shows excellent bifunctional activity, with an HER overpotential of 44 mV at 10 mA cm−2 and an OER overpotential of 305 mV at 50 mA cm−2 in alkaline electrolyte. In addition, it is worth noting that the overpotential of HER and OER at 500 mA cm−2 are only 229 mV and 368 mV, respectively. It is evidenced that the combination of Ni5Mo and NiCo2O4 transfers electrons from Co2+/Co3+ to Ni0/Mo0, which optimizes the electronic structures of the active sites of Ni0, Mo0 and Co3+, thus greatly enhances the intrinsic HER and OER activities. When Ni5Mo/NiCo2O4/NF is used as anode and cathode for water splitting under alkaline conditions, a stable current density of 10 mA cm−2 can be achieved at a low cell voltage of 1.54 V and a long-term stability up to 50 h. This work highlights the synergy effect of alloy and oxide heterojunctions in efficient water electrocatalysis.