Controlled synthesis of M doped N-Ni3S2 (M = Cu, Fe, Co and Ce) on Ni foam as efficient electrocatalyst for urea oxidation reaction and oxygen evolution reaction

Replacing fossil fuels by electrocatalytic water splitting for producing hydrogen and oxygen is one of the most promising ways to solve the energy crisis and environmental pollution. In this work, a series of M doped N-Ni3S2 (M = Cu, Fe, Co and Ce) material was firstly synthesized and in situ grown on nickel foam substrate by a typical two-step hydrothermal synthesis method. Two probe reactions, water oxidation and urea oxidation, were selected to investigate the catalytic performance of these materials. What is noteworthy is that the Fe doped N-Ni3S2 material exhibits superior water oxidation properties with requiring only 270 mV of overpotentials to drive current densities of 100 mA cm−2, which is one of the best activities reported so far. After a long time of durability measurement, the current density of the Fe doped N-Ni3S2 material will be attenuated, suggesting that the surface of the material will be in situ oxidized to oxide or hydroxide, which is the true active species. For urea oxidation, the Co doped N-Ni3S2 material shows superior catalytic performance with requiring only 1.36 V potentials to drive 100 mA cm−2 current densities. Density functional theory (DFT) calculation shows that different adsorption energy of water for N-Ni3S2, N-Cu-Ni3S2, N-Fe-Ni3S2 and N-Co-Ni3S2 leads to the different catalytic activity. Experimental results demonstrate that the improved catalytic performance is assigned to faster electron transfer rates, exposure of abundant active center and better conductivity due to N and cation doping. This work provides new lessons for doping engineering for water splitting reactions.