Surface Engineering on Ag-Decorated Co<sub>3</sub>O<sub>4</sub> Electrocatalysts for Boosting Nitrate Reduction to Ammonia
Ming Zhang, Zhipeng Ma, Shujie Zhou, Han Chen, Varun Kundi, Priyank V. Kumar, Lars Thomsen, Bernt Johannessen, Lingyi Peng, Yihao Shan, Constantine Tsounis, Yuwei Yang, Jian Pan, Rose Amal
Abstract
Electrochemical nitrate reduction reaction (NO 3 – RR) offers an alternative pathway toward ambient ammonia production and nitrogen balance restoration, requiring efficient catalysts. In this study, a silver-decorated cobalt oxide (Ag–Co 3 O 4 ) catalyst was shown to enhance ammonia production during NO 3 – RR in an alkaline electrolyte. Specifically, the Ag–Co 3 O 4 catalyst delivers an ammonia (NH 3 ) yield rate of 52 μmol h –1 cm –2 with a Faradaic efficiency of 88% at −0.32 V versus RHE. The activity is 6 times higher than that of the conventional Co 3 O 4 catalyst (8.8 μmol h –1 cm –2 ). The catalytic activity and selectivity of Ag–Co 3 O 4 originate from the interaction between atomically dispersed Ag and Co 3 O 4, resulting in the formation of active octahedral Co 2+ species (Co 2+ Oh ) with an unpaired e g electron, which facilitates the activation and adsorption of NO 3 – ion and promotes the *NO 2 adsorption, along with its transformation to *NO intermediate. This leads to efficient NH 4 + production, as evidenced by combined experimental and theoretical studies.