Cobalt-Based Electrocatalysts for Nitrate/Nitrite Reduction to Ammonia: Multiscale Design of Active Sites, Frameworks, and Interfaces.

Ammonia has recently emerged as a promising energy carrier in achieving carbon neutrality. Electrocatalytic nitrate/nitrite reduction reaction (NOx -RR) to ammonia offers a compelling alternative to the Haber-Bosch process, providing a viable pathway toward ambient ammonia production while simultaneously remediating environmental pollutants. However, balancing the adsorption and activation of reactant and stimulating the hydrogenation of key intermediates remain challenging during this complicated reaction, limiting the selectivity and ammonia yield rates. In this context, cobalt (Co)-based electrocatalysts have emerged as one of the most promising catalysts for NOx - reduction owing to their versatile electronic structures and tunable active centers. In this review, we summarize recent progress of advanced Co-based electrocatalysts in NOx -RR, introducing the correlation between electrochemical catalytic activity and their structural characteristics, with an emphasis on multiscale design of active centers, structural frameworks, and interfacial microenvironments. Additionally, we propose solutions to address the current challenges toward the practical ammonia synthesis. This review will provide valuable insights for the rational design of efficient and sustainable electrocatalysts for NOx - to ammonia.