Theory-guided construction of Cu-O-Ti-Ov active sites on Cu/TiO2 catalysts for efficient electrocatalytic nitrate reduction

Electrocatalytic nitrate reduction reaction (NO3RR) has been capturing immense interest in the industrial application of ammonia synthesis, and it involves complex reaction routes accompanied by multi-electron transfer, thus causing a challenge to achieve high efficiency for catalysts. Herein, we customized the Cu-O-Ti-Ov (oxygen vacancy) structure on the Cu/TiO2 catalyst, identified through density functional theory (DFT) calculations as the synergic active site for NO3RR. It is found that Cu-O-Ti-Ov site facilitates the adsorption/association of NOx– and promotes the hydrogenation of NO3– to NH3 via adsorbed *H species. This effectively suppresses the competing hydrogen evolution reaction (HER) and exhibits a lower reaction energy barrier for NO3RR, with the reaction pathways: NO3* → NO2* → HONO* → NO* → *NOH → *N → *NH → *NH2 → *NH3 → NH3. The optimized Cu/TiO2 catalyst with rich Cu-O-Ti-Ov sites achieves an NH3 yield rate of 3046.5 μg h–1 mgcat–1 at –1.0 V vs. RHE, outperforming most of the reported activities. Furthermore, the construction of Cu-O-Ti-Ov sites significantly mitigates the leaching of Cu species, enhancing the stability of the Cu/TiO2 catalyst. Additionally, a mechanistic study, using in situ characterizations and various comparative experiments, further confirms the strong synergy between Cu, Ti, and Ov sites, which is consistent with previous DFT calculations. This study provides a new strategy for designing efficient and stable electrocatalysts in the field of ammonia synthesis.