3D Flower‐Like Zinc Cobaltite for Electrocatalytic Reduction of Nitrate to Ammonia under Ambient Conditions.

Nitrate (NO3−) as a common pollutant of groundwater causes drinking water safety problems and seriously endangers people's health. Electrochemical reduction of nitrate to ammonia under ambient condition is a green and significant route to reduce the concentration of NO3− and produce ammonia (NH3), known as a complement to the Haber–Bosch reaction. Currently, noble‐metal electrocatalysts are often used in electrochemical reduction of NO3−, but high cost and scarcity limited their application. Herein, three‐dimensional (3D) flower‐like zinc cobaltite (ZnCo2O4) electrocatalyst was developed to convert nitrate into ammonia at room temperature. The NH3 yield rate could reach up to around 2100 μg mg−1 h−1 at a potential of −0.6 V vs. reversible hydrogen electrode (RHE), which was around 2.0 times higher than that of pristine Co3O4. In addition, the NH3 faradaic efficiency of ZnCo2O4 electrocatalyst could reach around 95.4 % at potential of −0.4 V vs. RHE with good structural and morphological stability, which surpassed most reported non‐noble metal‐based electrocatalysts. Further studies concluded that the improved activity of electrocatalytic NO3− reduction was ascribed to the existence of abundant active sites and the charge transfer from Co atoms to Zn atoms after Zn doping. Importantly, this work opens a new path for the development of Co‐based materials as electrocatalysts for reducing nitrate to ammonia. [ABSTRACT FROM AUTHOR]