Controlled synthesis of Co–Ni3Se2/MoS2/Ni3S2 nanoarrays as robust electrocatalyst for urea and seawater oxidation reaction

Hydrogen production through electrolysis of water is becoming more and more prominent in the preparation of renewable energy, but the shortage of traditional electrolyte forces us to search for brand new electrolytes. And urea and seawater , which are in large reserves and easily accessible, have become the mainstream electrolytes for hydrogen production. This paper reported the successful preparation of Co-doped Ni 3 Se 2 heterostructured catalysts with MoS 2 and Ni 3 S 2 heterogeneous structure in details by selenization and sulfidation of reactive metal oxides with hydroxide precursors. The Co–Ni 3 Se 2 /MoS 2 /Ni 3 S 2 target compounds showed excellent performance in the urea oxidation reaction (UOR), requiring only the potential of 1.281 V at a current density of 10 mA∗cm −2 comparing with other catalysts while possessing a smaller Tafel slope as well as a larger double-layer capacitance, which was also reflected in impedance spectra. The result indicated that the target catalysts possessed a good urea oxidation reaction performance in all aspects. The oxygen evolution reaction (OER) performance also performed equally well in seawater electrolyte, a current density of 10 mA∗cm −2 was achieved with only overpotential of 164 mV. It should be noted, however, that the material was not stable in the urea and seawater tests, and further optimization work is needed to improve the stability of the electrode. The adsorption energies of the electrode components for urea molecules were analyzed by Density Functional Theory (DFT) calculations to further reveal the importance of the heterogeneous structure of the electrode during the UOR reaction. Co–Ni 3 Se 2 /MoS 2 /Ni 3 S 2 nanoarrays were investigated as catalysts with good catalytic activity in urea and oxygen evolution reaction. • Co–Ni 3 Se 2 /MoS 2 /Ni 3 S 2 materials were successfully synthesized by hydrothermal processes. • Co–Ni 3 Se 2 /MoS 2 /Ni 3 S 2 electrode shows excellent catalysis in the cathode reaction of urea and seawater. • Density Functional Theory (DFT) calculations demonstrated that Ni 3 S 2 possesses an optimal urea adsorption energy.