Fe and Cu Double-Doped Co 3 O 4 Nanorod with Abundant Oxygen Vacancies: A High-Rate Electrocatalyst for Tandem Electroreduction of Nitrate to Ammonia.

The electrochemical nitrate reduction reaction (NO 3 RR) is an attractive green alternative to the conventional Haber-Bosch method for the synthesis of NH 3 . However, this reaction is a tandem process that involves multiple steps of electrons and protons, posing a significant challenge to the efficient synthesis of NH 3 . Herein, we report a high-rate NO 3 RR electrocatalyst of Fe and Cu double-doped Co 3 O 4 nanorod (Fe 1 /Cu 2 -Co 3 O 4 ) with abundant oxygen vacancies, where the Cu preferentially catalyzes the rapid conversion of NO 3 - to NO 2 - and the oxygen vacancy in the Co 3 O 4 substrate can accelerate NO 2 - reduction to NH 3 . In addition, the introduction of Fe can efficiently capture atomic H* that promotes the dynamics of NO 2 - to NH 3 , improving Faradaic efficiency of the produced NH 3 . Controlled experimental results show that the optimal electrocatalyst of Fe 1 /Cu 2 -Co 3 O 4 exhibits good performance with high conversion (93.39%), Faradaic efficiency (98.15%), and ammonia selectivity (98.19%), which is significantly better than other Co-based materials. This work provides guidance for the rational design of high-performance NO 3 RR catalysts.