Ternary W-Co-Mo oxide solid solutions for high efficiency electrocatalytic nitrate reduction to ammonia

Electrocatalytic nitrate (NO 3 - ) reduction reaction (NO 3 RR) offers a sustainable pathway to mitigate nitrate-contaminated water and enable ammonia (NH 3 ) production. However, the trade-off between Faradaic efficiency (FE) and NH 3 yield at low overpotentials, arising from poor water dissociation ability and sluggish multi-electron/proton transfer kinetics, remains a critical bottleneck. Herein, we report a ternary W-Co-Mo oxide solid solution (CWMO) synthesized via a one-pot hydrothermal method, which uniquely integrates oxygen vacancies and trimetallic active sites to overcome this limitation. Electrochemical measurements reveal that CWMO achieves a FE of 90% and a high NH 3 yield of 3.95 mg h −1 cm −2 at −0.4 V versus reversible hydrogen electrode (RHE), significantly outperforming CWO and CMO. Mechanistic studies, including electrochemical impedance spectroscopy, Bode plot analysis and in situ spectroscopic analyses, indicate that the W-Co-Mo sites accelerate water dissociation, providing an adequate supply of active hydrogen for NO 3 - hydrogenation, while oxygen vacancies enhance NO 3 - adsorption and activation, thus enhancing catalytic performance. This work establishes ternary oxide solid solutions as a promising platform for high-performance NO 3 RR electrocatalysts and provides fundamental insights into synergistic effects between oxygen vacancies and multimetallic sites in complex electrocatalytic transformations.