Transition metal atoms M (M = Mn, Fe, Cu, Zn) doped nickel-cobalt sulfides on the Ni foam for efficient oxygen evolution reaction and urea oxidation reaction

Abstract

Electrolysis of water is an environmentally friendly and promising hydrogen generation technology, which is one of the best ways to deal with the global energy crisis and environmental pollution. However, the slow anode reaction of water electrolysis is the bottleneck of limiting the efficient hydrogen production. Therefore, it is a key problem to explore an efficient and economical electrocatalyst to assist the anode reaction. Herein, a series of self-supporting M-NiCo2S4 /Ni3S2 (M=Mn, Fe, Cu, Zn) nanostructures grown on a nickel foam (NF) skeleton were prepared through one-step hydrothermal strategy. In this process, doping engineering is employed to adjust the electronic structure of catalyst and improve the performance of the catalyst. Among them, the introduction of Fe not only greatly changed the morphology, but also provided rich active sites. Specifically, the Fe-NiCo2S4/Ni3S2 electrode can achieve current densities of 50 and 100 mA cm−2 at overpotential of 159 and 210 mV in alkaline media for oxygen evolution reaction (OER). In addition, driving current densities of 50 and 100 mA cm−2 in 1.0 M KOH with 0.5 M urea only requires the ultra-small voltage of 1.37 and 1.39 V (vs. RHE) for urea oxidation reaction (UOR), indicating that UOR can well replace OER to reduce electrical energy consumption. The experimental results and density functional theory calculations (DFT) demonstrate that the superior activity of the catalyst can be attributed to the optimal water adsorption energy, faster electron transfer rate, more active site exposure and good electrical conductivity. This work extends the application of doping engineering in water electrolysis and provides a novel preparation method of efficient catalyst for OER and UOR.