Interfacial Electronic Engineering of the 2D/2D Cu‐MoS ₂ /Cu ₃ (HIB) ₂ Heterojunction for Bifunctional Ammonia Electrolysis: Synergistic Hydrogen Production and Wastewater Detoxification

Abstract The electrocatalytic ammonia oxidation reaction (eAOR) holds great potential for sustainable hydrogen production but is limited by sluggish kinetics. In this study, a novel 2D/2D heterojunction, Cu‐MoS 2 /Cu 3 (HIB) 2 (HIB: 1,2,3,4,5,6‐hexachlorobenzene), is fabricated via in situ growth of a conductive copper‐based metal–organic framework (Cu 3 (HIB) 2 ) around Cu‐doped MoS 2 . This heterojunction integrates abundant sulfur vacancies, modulates electron density at active sites, and facilitates rapid electron transfer. As a result, it exhibits significantly enhanced eAOR and hydrogen evolution reaction (HER) performance compared to individual components. The assembled electrolyzer achieves ≈100% ammonia removal and a high hydrogen production rate of 15.3 mL h −1 at 1.60 V versus RHE. In situ Fourier transform infrared (FT‐IR) spectroscopy and density functional theory analyses reveal that S vacancies and Cu doping induce electron localization and orbital hybridization (Cu 3 d , Mo 4 d , S 2 p ), stabilizing Mo active sites and promoting ammonia (NH 3 ) adsorption and activation. The formation and transformation of intermediates are optimized, facilitating the selective conversion of NH 3 to nitrogen (N 2 ). This study provides valuable insights into the design of bifunctional electrocatalysts via dimensional heterojunctions and demonstrates a promising strategy for coupling wastewater treatment with hydrogen production.