Heterojunction electrocatalysts for nitrate reduction to ammonia: interfacial synergistic mechanisms and emerging applications

Electrocatalytic nitrate reduction reaction (NO 3 RR) for ammonia synthesis is a key technology that integrates environmental pollution treatment with green energy production. However, the complex eight-electron nine-proton transfer process of NO 3 RR imposes conflicting requirements on the electronic structure and active sites of single-component catalysts, leading to bottlenecks such as low ammonia yield, poor selectivity, and severe hydrogen evolution reaction (HER) competition. Heterojunction catalysts, constructed by interfacing different material components, offer a promising strategy for addressing these challenges through interfacial interactions. This review discusses selected recent advances in heterojunction electrocatalysts for NO 3 RR. It first dissects four core interfacial synergistic mechanisms by which heterojunctions enhance NO 3 RR performance: built-in electric field effect, tandem catalysis effect, hydrogen spillover effect, and electronic structure modulation. Subsequently, representative heterojunction catalyst systems are classified and discussed according to component types, with a focus on their exploration in device applications such as Zn-NO 3 − batteries and coupled anodic oxidation. Finally, the challenges and future directions are envisioned, aiming to provide a systematic reference for the rational design of more efficient and stable heterojunction catalysts for NO 3 RR.