Electronic modulation of Cu sites by Co for selective nitrate reduction to ammonia

Electrocatalytic reduction of nitrate (NO 3 RR) to ammonia is considered as a promising strategy for nitrogen resource recovery from nitrate-contaminated water. However, conventional Cu-based catalysts often suffer from poor selectivity, with toxic nitrite accumulation and sluggish reduction kinetics. This work reports a Cu Co co-loaded carbon catalyst (CuCo-C) that leverages electron-deficient Cu sites in synergy with Co to significantly enhance the NO 3 RR activity and ammonia selectivity. The optimized CuCo-C discloses a nitrate removal rate of 94 %, an ammonia selectivity of 99 % and multi-turn stability. The combination of comprehensive surface analysis and experimental techniques reveals that the high NO 3 − -to-NH 4 + performance results from Co-induced electronic modulation of Cu sites. This synergistic effect not only kinetically facilitate the adsorption and activation of NO 3 − but also enhance the selectivity of key intermediate (NO 2 − ) towards NH 4 + formation. Density Functional Theory (DFT) calculations and synchrotron radiation-based XAFS measurements further reveal the presence of Co promotes the adsorption of NO 3 − (forming *NO 3 ), lowers the energy barrier for *NO 3 to *NO 2 deoxygenation and simultaneously suppresses the competing H 2 evolution reaction. Importantly, the presence of Co promotes the conduction of the electron reduction path by CuCo-C to generate NH 4 + . This work provides valuable insights for the rational design of high-performance Cu-based electrocatalysts for sustainable nitrate remediation and ammonia synthesis.