Hydrogen spillover as an interfacial strategy for nitrate electroreduction to ammonia

Nitrate electroreduction to ammonia (NRA) offers a route for ammonia recovery from nitrate-containing water streams while contributing to water remediation. However, its multi-step deoxygenation and hydrogenation pathway exhibits suboptimal efficiency. Rational electrocatalyst design is central to overcoming this bottleneck. Hydrogen spillover spatially decouples water-dissociation-driven H* supply from substrate hydrogenation, providing an interfacial strategy to balance activity and selectivity. This review methodically examines recent advancements in hydrogen-spillover-enhanced NRA. Catalyst design is discussed from five aspects: electronic structure engineering of Cu-based catalysts, donor and reduction phase coupling, H* migration direction control, migration pathway shortening, and interfacial microenvironment regulation. This comprehensive strategy is meticulously designed to enhance ammonia production rate and faradaic efficiency. Concurrently, we synthesize the principal characterization techniques currently deployed to probe hydrogen spillover and highlight their mechanistic diagnostic value. We conclude by identifying the outstanding challenges and future directions in this field.