Advanced Ruthenium‐Based Electrocatalysts for NO _x Reduction to Ammonia

Abstract Ammonia (NH ₃ ) is widely recognized as a crucial raw material for nitrogen‐based fertilizer production and eco‐friendly hydrogen‐rich fuels. Currently, the Haber–Bosch process still dominates the worldwide industrial NH ₃ production, which consumes substantial energy and contributes to enormous CO ₂ emission. As an alternative NH ₃ synthesis route, electrocatalytic reduction of NO _x species (NO ₃ ⁻ , NO ₂ ⁻ , and NO) to NH ₃ has gained considerable attention due to its advantages such as flexibility, low power consumption, sustainability, and environmental friendliness. This review timely summarizes an updated and critical survey of mechanism, design, and application of Ru‐based electrocatalysts for NO _x reduction. First, the reason why the Ru‐based catalysts are good choice for NO _x reduction to NH ₃ is presented. Second, the reaction mechanism of NO _x over Ru‐based materials is succinctly summarized. Third, several typical in situ characterization techniques, theoretical calculations, and kinetics analysis are examined. Subsequently, the construction of each classification of the Ru‐based electrocatalysts according to the size of particles and compositions is critically reviewed. Apart from these, examples are given on the applications in the production of valuable chemicals and Zn−NO _x batteries. Finally, this review concludes with a summary highlighting the main practical challenges relevant to selectivity and efficiency in the broad range of NO _x concentrations and the high currents, as well as the critical perspectives on the fronter of this exciting research area.