Built‐In Electric Field Engineering at Heterojunction Interfaces for High‐Performance Urea Electrocatalysis

Abstract The urea oxidation reaction (UOR) is regarded as a promising pathway for electrocatalytic hydrogen production due to its significantly lower theoretical voltage compared to conventional water oxidation. Reasonable charge distribution is crucial for enhancing urea molecule adsorption and bond cleavage, which can be optimized through rational heterostructure design. In this study, a novel heterojunction catalyst (i.e., Ni 3 Se 2 @NiMoO 4 /NF), featuring a built‐in electric field, is synthesized. This architecture creates an electrophilic region on the Ni 3 Se 2 side and a nucleophilic region on the NiMoO 4 side, facilitating selective activation of electron‐withdrawing and electron‐donating groups in the urea molecule. Thereby accelerating C─N bond dissociation. The catalyst exhibits exceptional UOR performance, attaining a current density of 100 mA cm −2 at a 1.31 V (vs reversible hydrogen electrode) record‐low potential, with sustained operation exceeding 140 h. Furthermore, it functions as a bifunctional catalyst in a UOR||HER system, achieving 10 mA cm −2 at 1.35 V, with sustained operation over 168 h. This study elucidates the reaction mechanism of urea electrooxidation at the molecular level and demonstrates that the built‐in electric field can precisely modulate charge distribution during the catalytic process. These insights offer a strategic pathway for the development of high‐efficiency, energy‐saving urea‐assisted hydrogen production systems.