Quenching-assisted surface functionalization of metal oxide for highly enhanced electrocatalytic urea oxidation

Abstract

Urea oxidation reaction (UOR) is considered as a good substitute for oxygen evolution reaction (OER) because of its low theoretical onset potential. Surface modification is an effective strategy to tune the catalytic activity of the catalysts towards UOR. Here, we developed a facile and universal quenching strategy to prepare sulfate-modified NiO nanosheets (NiO@NF-20S). Compared with the pristine NiO nanosheets, the electrocatalytic performance of the NiO@NF-20S is greatly improved, showing a small potential of 1.40 V vs. RHE to deliver a current density of 200 mA cm⁻² as well as robust electrochemical stability. The outstanding electrocatalytic performance of the NiO@NF-20S is mainly ascribed to the improved surface wettability and the promoted Ni²⁺/Ni³⁺ redox reaction. The quenching strategy can be expanded to not only various kinds of functional groups from nitric acid and phosphoric acid but also other metal oxides such as NiCoO_x and NiCrO_x. This work provides a new avenue to the design of surface-functionalized metal oxide catalysts for electrocatalysis.