Different M-doped Ni3S2/FeS (M=Co, Cr, Cu, Zn) hybrid nanosheet arrays for overall urea splitting and seawater oxidation reaction

Abstract

Hydrogen production by electrolysis of water is gradually becoming the main way to obtain green energy, but due to the scarcity of fresh water resources in the world, so the study of urea and seawater electrolysis has become an important work. In this experiment, different metal ions M (M=Co, Cr, Cu, Zn) doped Ni3S2/FeS were investigated as catalysts with good catalytic activity in hydrogen evolution reaction (HER) as well as in urea oxidation reaction (UOR) in urea electrolyte, and Co-Ni3S2/FeS and Cr-Ni3S2/FeS, which performed well in HER and UOR, were assembled into an electrolytic cell for the overall urea decomposition (1.50 V @ 10 mA cm−2). Density Functional Theory (DFT) calculations demonstrated that Co-Ni3S2 possesses a lower free energy for H, while FeS possesses a higher density of states (DOS) near the Fermi energy level, and such a composite structure promotes significantly the catalytic activity of HER. The catalytic effect of oxygen evolution reaction (OER) was further investigated in the seawater electrolyte, and the results showed that the performance of Co-Ni3S2/FeS catalyst was better, and certain ions in seawater affected durability of the catalyst. The electronic structure of the catalyst was investigated through the characterization of the catalyst and combined with the special morphology jointly promote the catalytic reaction in electrolysis experiments, which provides a candidate catalyst for electrolysis of urea and seawater oxidation reaction.