Unraveling Tandem Catalytic Sites for Electrocatalytic Nitrate Reduction to Ammonia

Abstract Nitrate (NO 3 − ) pollution from industrial and agricultural sources poses significant threats to water quality and human health. The electrocatalytic nitrate reduction reaction (NIRR), which converts NO 3 − into high‐value ammonia (NH 3 ), offers an efficient approach for treating NO 3 − ‐containing wastewater while addressing energy‐related challenges. Generally, NIRR is a multi‐step reaction, and its core steps‐NO 3 − activation and hydrogenation‐correspond to the NO 3 − adsorption sites and hydrogenation sites on the catalyst, respectively. The tandem catalytic sites accelerate reaction kinetics by spatially separating NO 3 − adsorption sites from hydrogenation sites and leveraging multifunctional catalytic sites for tandem catalysis. Consequently, tandem catalytic sites have recently emerged as an effective strategy for electrocatalytic NIRR. Nevertheless, a comprehensive understanding of the underlying mechanism remains limited. This review begins by outlining the advantages of tandem catalytic sites and recent advances in representative catalysts. It then highlights in situ characterization techniques used to elucidate reaction intermediates and tandem catalytic sites. Finally, applications and economic analysis in wastewater treatment, sustainable NH 3 synthesis, and energy conversion are systematically discussed. The review concludes with a perspective on complex NO 3 − wastewater treatment, NH 3 purification, environmental catalytic flow battery, and economic feasibility analysis, emphasizing their roles in sustainable energy solutions.