Ni modified Co2VO4 heterojunction with poor/rich-electron structure for overall urea-rich wastewater oxidation

Constructing heterojunction is an effective method to design catalysts for accelerating the sluggish kinetics of urea oxidation reaction (UOR) at large current density. Herein, Ni modified mesoporous Co2VO4 nanosheets with heterojunction structure is synthesized on nickel foam (Ni-Co2VO4/NF) by hydrothermal and calcination method. It shows good activity for UOR (eta(10/500/1,000) = 1.28/1.38/1.45 V) and hydrogen evolution reaction (HER, eta(-10/-500/-1,000) = 50/267/329 mV). Overall urea oxidation (OUO, eta(10) = 1.36 V) can maintain long-term stability at 500 mA cm(-2) for 140 h without significant activity decrease. This good activity could be due to the strongly coupled heterojunction of Ni and Co2VO4 that can modulate the interfacial electronic structure to form poor/rich-electron species for promoting urea/H2O adsorption and improving its UOR/HER intrinsic activity. Meanwhile, the mesoporous nanosheets structure with large specific surface area can expose more active sites and facilitate the desorption of bubbles on the electrode surface for improving UOR/HER reaction kinetics and stability at large current density. This work thus designs an efficient and stable bifunctional catalyst for urea-assisted hydrogen production at large current density.