Building dual active sites Co3O4/Cu electrode to break scaling relations for enhancement of electrochemical reduction of nitrate to high-value ammonia.

The electrochemical reduction of nitrate to ammonia (ERNA) has become a green treatment technology for nitrate wastewater. However, strong adsorption for product caused high activation energy for product desorption in scaling relations, blocking activity of electrocatalyst in ERNA. Density functional theory (DFT) calculations indicated that constructing dual active sites (Cu and Co3O4) could achieve strong adsorption of nitrate (-2.91 eV) with low desorbing energy barrier of ammonia (0.13 eV), breaking scaling relations. This dual active sites Co3O4/Cu electrode achieved a high ammonia yield rate of 684 µg mgcat-1 h-1 with 94.6% faradic efficiency, surpassing single active site Co3O4 and Cu electrodes. For mechanism, In-situ electrochemical characterization found the vital intermediates of *NH and *NH2, demonstrating that indirect reduction was the main pathway on Co3O4/Cu electrode. Thus, it is believed that building dual active sites on electrode is a reliable strategy to enhance ERNA for purifying industrial wastewater polluted by nitrate.