CuCo2O4@ACoNi-LDH (A=Fe, Cu, Zn, Cr) as efficient electrocatalyst for freshwater, seawater and urea oxidation reaction

Water electrolysis has a promising prospect in the production of green hydrogen energy, but its oxygen evolution reaction kinetics is relatively slow. Therefore, in this experiment, CuCo2O4@ACoNi-LDH (A = Fe, Cu, Zn, Cr) with heterogeneous core-shell catalytic material was firstly prepared by means of hydrothermal and calcination process, and its anodic oxidation reaction in freshwater, seawater and urea was investigated. In the oxygen evolution reaction (OER) of electrolytic water, CuCo2O4@CuCoNi-LDH displays the best catalytic activity. When the current density is 10 mA cm−2, only the overpotential of 199 mV is needed (potential of 1.429 V). The competitive oxidation and corrosion of chloride ions in seawater result in the decrease of catalytic activity. For urea oxidation reaction (UOR), CuCo2O4@FeCoNi-LDH displays the best catalytic performance, only potential of 1.292 V was required with the same current density, and the catalyst had good stability during the reaction for 12 h. Density functional theory calculation shows that CuCo2O4 plays an important role in the catalytic process. The synergistic catalysis of FeCoNi-LDH and CuCo2O4 results in the improvement of catalyst activity and stability. The CuCo2O4 material plays a key role in catalyzing urea splitting and the FeCoNi-LDH material protects CuCo2O4 from corrosion according to experimental results and density functional theory calculations. This experiment provides a new idea for the hydrogen production, exploration and the treatment of urea wastewater for transition metal oxides and layered hydroxides electrocatalyst with core-shell heterostructure.