Leveraging hydrogen spillover for advanced electrocatalysts in nitrate-to-ammonia conversion

This review comprehensively summarizes recent progress in hydrogen spillover-enhanced nitrate-to-ammonia electrocatalysts. A particular focus is placed on material design strategies, including single-atom catalysts, alloys, metal oxides, and heterostructures, for boosting ammonia yield and Faradaic efficiency. • •This review explores hydrogen spillover’s critical role in enhancing NRA. • • Key catalyst design principles for harnessing hydrogen spillover effect are outlined. • •Advanced techniques for characterizing the hydrogen spillover process are summarized. • • Current challenges and promising future research of NRA are discussed. The electrocatalytic nitrate reduction to ammonia (NRA) represents an attractive route for sustainable ammonia synthesis and environmental nitrate pollution remediation. However, its practical application is plagued by inadequate efficiency and selectivity, stemming from a complex, multi-step reaction mechanism. Overcoming these hurdles requires advanced electrocatalyst design, wherein the hydrogen spillover effect emerges as a pivotal mechanism for modulating active sites and accelerating reaction kinetics. This review comprehensively delineates recent progress in hydrogen spillover-enhanced NRA catalysis. It critically examines innovative material design strategies, including single-atom catalysts, alloys, metal oxides, and heterostructures, for enhancing the ammonia yield and Faradaic efficiency. A dedicated focus is placed on advanced operando characterization techniques that enable the direct observation of hydrogen spillover and decipher its role in reaction mechanisms and intermediate evolution. Finally, the review outlines persistent challenges and proposes future directions for catalyst development and mechanistic studies.