Construction of an Internal Charge Field: CoS1.097/Ni3S2 Heterojunction Promotes Efficient Urea Oxidation Reaction

Abstract

Urea oxidation reaction (UOR) features a lower overpotential compared to the oxygen evolution reaction (OER) during electrolysis, facilitating the hydrogen evolution reaction (HER) at the cathode. The distribution of charge plays a pivotal role in promoting the adsorption and cleavage of chemical groups in urea molecules, which can be modulated by introducing a heterostructure. Herein, a CoS_1.097/Ni₃S₂ heterojunction grown on nickel foam is designed, serving simultaneously for UOR and HER. Based on density functional theory (DFT) calculations, the spontaneous charge transfer at the CoS_1.097/Ni₃S₂ heterointerface induces the formation of localized electrophilic/nucleophilic regions, intelligently adsorbing electron-donating/electron-withdrawing groups in urea molecules, activating chemical bonds, thereby triggering urea decomposition. CoS_1.097/Ni₃S₂ exhibits excellent catalytic activity for urea, requiring only a potential of 1.22 V (with an overpotential of 0.85 V) to achieve a current density of 100 mA cm⁻² in UOR, and potentials of 1.27 and 1.57 V to reach current densities of 10 and 100 mA cm⁻², respectively, in a UOR//HER electrolysis cell, maintaining good stability at high current density for 60 h. Tests in real urine have demonstrated performance similar to that in urea electrolyte. This work represents nearly the best catalytic performance of transition metal-based materials in UOR applications, promising for both efficient hydrogen production and urea decomposition.