Molecular‐Level Engineered Approach Induces Built‐in Electric Field Modulation in G‐C ₃ N ₄ /CoMoS ₂ Heterojunction for Enhanced Hydrogen Generation via Urea Oxidation

ABSTRACT Urea‐assisted electrolysis boosts hydrogen production by substituting the sluggish oxygen evolution reaction (OER) with the energetically favorable urea oxidation reaction (UOR), thereby lowering energy consumption. Rational heterojunction engineering modulates charge distribution and generates abundant active sites, facilitating urea adsorption and C─N bond cleavage. Herein, we report a facile electrodeposition strategy to construct g‐C ₃ N ₄ /CoMoS ₂ hybrid electrocatalysts. The built‐in electric field at the heterojunction creates electrophilic regions on g‐C ₃ N ₄ and nucleophilic regions on CoMoS ₂ , selectively activating urea and promoting rapid bond cleavage. Anchoring g‐C ₃ N ₄ onto CoMoS ₂ enables remarkable bifunctional activity toward both UOR and HER, achieving potentials of 1.27 V vs. RHE in 1 m KOH + 0.33 m urea and ‐80 mV vs. RHE in 1 m KOH at 10 mA cm ⁻² , respectively. Density functional theory (DFT) calculations reveal that interfacial electron transfer enriches CoMoS ₂ with electrons and depletes g‐C ₃ N ₄ , enhancing charge transfer, optimizing urea adsorption, and lowering reaction energy barriers. Notably, the g‐C ₃ N ₄ /CoMoS ₂ //g‐C ₃ N ₄ /CoMoS ₂ cell delivers 10 mA cm ⁻² at 1.34 V with excellent stability, demonstrating superior efficiency. This work provides a rational framework for designing efficient, energy‐saving urea‐assisted hydrogen production systems and reveals how intrinsic electric fields can precisely control charge distribution during catalysis.