Electronic structure modulation of a Mo-doped NiO/Ni bifunctional electrocatalyst for efficient urea-assisted water splitting

Abstract

Urea oxidation-assisted hydrogen production provides an energy-efficient and sustainable alternative to conventional water electrolysis by significantly reducing the required cell voltage. However, developing bifunctional catalysts with high activity, long-term stability and bifunctionality remains an ongoing challenge. Here, the electronic structure of NiO/Ni is precisely modulated through molybdenum (Mo) incorporation, enabling simultaneous enhancement of the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). The resulting Mo–NiO/Ni catalyst, obtained via simple electrodeposition followed by an annealing approach, exhibits outstanding activity and durability, requiring cell voltages of 1.33 and 1.62 V to achieve 10 and 100 mA cm⁻², respectively, for overall urea electrolysis, which are 170 and 200 mV lower than those of overall water electrolysis under the same conditions. Density functional theory (DFT) calculations reveal that Mo doping optimizes the electronic configuration of NiO/Ni, lowers the activation barrier of urea dehydrogenation and approaches thermoneutral hydrogen adsorption. This work demonstrates an effective electronic structure engineering strategy for designing efficient bifunctional catalysts toward low-energy hydrogen production coupled with urea degradation.