Enhanced urea oxidation catalysis through Ni single-atom doping on Cu2O surfaces: a computational study

Abstract

The electrocatalytic urea oxidation reaction (UOR), featuring a low equilibrium potential, emerges as a promising alternative to the conventional oxygen evolution reaction. However, the UOR suffers from intrinsically sluggish kinetics due to its six-electron, proton-coupled nature, underscoring the need for the development of highly efficient catalysts. In this work, we have meticulously probed the urea oxidation activities over Ni single-atom doped Cu₂O (Ni–Cu₂O) and elucidated their underlying mechanisms. The Ni single atom substituted a copper atom on the surface/subsurface of Cu₂O:{110}_Cu and Cu₂O:{111}_O. The theoretical calculation results demonstrated that the Ni–Cu₂O:{110}_Cu configuration exhibits optimal urea adsorption energy, which is conducive to effectively activating the urea molecule and lowering the energy barriers of the subsequent dehydrogenation and nitrogen–nitrogen coupling. The enhanced catalytic performance is primarily due to the synergistic interplay between the surface copper atoms and the single nickel atom within the Ni–Cu₂O:{110}_Cu structure. This synergy facilitates the activation of nitrogen in urea by the nickel atom, while the copper atoms robustly adsorb oxygen from urea, collectively modulating the π-electron distribution within the urea molecule to activate N–H and C–N bonds. Remarkably, the overpotential for urea oxidation on this catalyst is only 0.29 V, establishing it as an exemplary candidate for urea electrooxidation. Our research not only unveils the cooperative mechanism intrinsic to Ni-doped Cu₂O for urea oxidation but also paves the way for innovative approaches in designing advanced electrocatalysts.