Ni3S2/MxSy–NiCo LDH (M = Cu, Fe, V, Ce, Bi) heterostructure nanosheet arrays on Ni foam as high-efficiency electrocatalyst for electrocatalytic overall water splitting and urea splitting

Here, we synthesized a series of Ni₃S₂/M_xS_y-NiCo LDH materials (M = Cu, Fe, V, Ce, and Bi) by a two-step hydrothermal method for the first time, which display excellent oxygen evolution reaction (OER) and urea oxidation reaction (UOR) properties. M (M = Cu, Fe, V, Ce, and Bi) ions were firstly doped into NiCo LDH to change the original electronic structure and enhance the activity of the LDH. Then, Ni₃S₂ and M_xS_y were introduced by sulfurization of the Ni support and doping cations, and the combination of Ni₃S₂, M_xS_y and NiCo-LDH improved the electron transfer rate and activity of the original material. With Ni₃S₂/Bi₂S₃-NiCo LDH/NF as anode and Ni₃S₂/CuS-NiCo LDH as cathode, an electrolytic cell can reach 10 mA cm^-2 at 1.622 V with outstanding durability for overall water splitting. In addition, with Ni₃S₂/Bi₂S₃-NiCo LDH/NF as both electrodes, it can reach 10 mA cm^-2 at 1.56 V with outstanding durability for overall urea splitting, which is better than that of the overall water splitting. Density functional theory (DFT) calculation shows that the superior electrocatalytic activity can be explained by the water adsorption energy being optimized and enhanced conductivity. This study provides a new idea for improving the catalytic activity and stability of non-noble metals instead of noble metals.