Nanoconfinement-driven electronic structure and local microenvironment modulation for electrochemical nitrate reduction to ammonia synthesis

The increasing severity of nitrate (NO 3 − ) contamination in aquatic systems underscores the urgent demand for efficient and sustainable remediation technologies. Electrochemical nitrate reduction to ammonia (NO 3 RR) presents a dual opportunity for environmental restoration and energy recovery, yet its practical application is constrained by challenges related to catalyst activity, selectivity, and stability. Nanoconfinement strategies have been identified as an effective means to overcome these limitations by maximizing active site exposure, modulating electronic structure, optimizing intermediate adsorption and diffusion, and enhancing local concentration effects. This review systematically examines the mechanistic pathways of NO 3 RR and summarizes recent advancements in nanoconfined catalysts, including nanoconfined single-atom catalysts, cluster catalysts, nanoparticle catalysts, and metal-compound catalysts. Particular emphasis is placed on how spatial confinement modulates physicochemical properties to suppress side reactions, stabilize key intermediates, and lower energy barriers, thereby accelerating reaction kinetics and improving ammonia selectivity. Furthermore, the synergistic contributions of confinement-induced electronic modulation and mass transport regulation are critically assessed. Finally, the principal challenges, such as maintaining catalyst durability under operational conditions and achieving precise nanoscale structural control, are outlined, and future perspectives for rational catalyst design are proposed. This review aims to offer fundamental insights into harnessing nanoconfinement effects to advance electrocatalytic NO 3 RR toward sustainable nitrogen management. • Nanoconfined catalysts show promise in nitrate-to-ammonia electrocatalysis. • The superiorities of the nanoconfinement effect are elucidated. • The different types of nanoconfined catalyst based on size considerations was highlighted. • The existing challenges and prospects of nanoconfined catalysts are proposed.