Generation of a Built‐In Electric Field in the Heterostructure MoS 2 /Ni3Se 2 Facilitates Hydrogen Production via Energy‐Saving Urea Oxidation

ABSTRACT The urea oxidation reaction (UOR) offers a sustainable and thermodynamically favorable alternative to the oxygen evolution reaction, enabling coupling of urea‐rich wastewater remediation with energy‐efficient hydrogen production. However, the sluggish six‐electron‐transfer kinetics of UOR necessitate advanced electrocatalysts to accelerate reaction dynamics. Heterostructure engineering provides an effective strategy to regulate interfacial charge redistribution and enhance catalytic activity. Herein, we report a rationally designed MoS 2 /Ni 3 Se 2 heterostructure with an intrinsic built‐in electric field, constructed on nickel foam via hydrothermal growth followed by electrodeposition, exhibiting efficient bifunctional electrocatalytic activity toward UOR and the hydrogen evolution reaction. Density functional theory calculations reveal spontaneous interfacial charge transfer at the MoS 2 /Ni 3 Se 2 interface, generating localized electrophilic and nucleophilic regions that facilitate urea adsorption, promote bond activation, and accelerate decomposition kinetics. Benefiting from this interfacial electronic modulation, the catalyst requires only 1.20 V vs. RHE to achieve 10 mA cm −2 for UOR in 1 M KOH + 0.5 M urea and an overpotential of 81 mV to reach the same current density for HER in 1 M KOH. Furthermore, the assembled UOR//HER electrolyzer operates at 1.31 V at 10 mA cm −2 and maintains stable performance for over 100 h. This work advances heterostructure‐based urea‐assisted hydrogen production for sustainable electrocatalysis.