Ammonia is considered to be a next‐generation clean energy carrier, and thus the green synthesis of NH3 is of great importance. In this work, non‐thermal plasma oxidation is combined with electroreduction to achieve an efficient two‐step NH3 synthesis. A Ti bubbler is introduced in the first step of plasma activation of air to effectively produce nitrate/nitrite (NOx−) in an absorption solution, and the production rate achieves the highest value of 55.29 mmol h−1; the obtained NOx− aqueous solution is directly employed as catholyte for the second step of electroreduction with oxygen vacancy‐rich Co3O4 nanoparticles as the catalyst. Density functional theory calculations reveal that the introduction of oxygen vacancies endows their adjacent Co atoms with improved activity, which promotes adsorption and hydrogenation of NOx−, meanwhile suppressing the hydrogen evolution reaction. Thus the oxygen vacancy‐rich Co3O4 NPs present a significant NH3 production rate of 39.60 mg h−1 cm−2, high Faradaic efficiency of 96.08% and a large current density (376.48 mA cm−2), outperforming the previously reported ones including N2 or NOx− electroreduction.

The traditional method for synthesizing NH3 is the Haber–Bosch process which results in high‐fuel consumption and environmental pollution. Therefore, ecofriendly electrochemical synthesis of NH3 through nitrate (NO3−) reduction is a good choice. Herein, an integral Au/Cu electrode to catalyze NO3− reduction to NH3 is introduced. The catalyst exhibits not only the highest NH3 yield rate (73.4 mg h−1 cm−2) up to now but also a very high Faradaic efficiency of 98.02% at −0.7 V at room temperature. It is commonly believed that the transformation of NO3− to nitrite (NO2−) is an obstacle to the NH3 generation from NO3− reduction. Surprisingly, unlike most of the other catalysts, Au/Cu exhibits better activity for NO3− reduction than that for NO2− reduction. Based on the detailed experimental and density functional theory calculations, the excellent performance of Au/Cu for selective NO3− reduction lies in the enhanced adsorption capabilities of Au/Cu to NO3− in the alkaline environment and the lower energy barriers of the electrochemical reduction reaction.

Ammonia (NH3) is essential for modern agriculture and industry, and due to its high hydrogen density and no carbon emission, NH3 is also expected to be the next‐generation of “clean” energy carrier. Herein, directly from air and water, the plasma‐electrocatalytic reaction system for NH3 production, which combines two steps of plasma‐air‐to‐NOx− and electrochemical NOx− reduction reaction (eNOxRR) with a bifunctional catalyst, have been successfully established. Especially, the bifunctional catalyst of CuCo2O4/Ni can simultaneously promote the plasma‐air‐to‐NOx− and eNOxRR processes. The easy adsorption and activation of O2 by CuCo2O4/Ni greatly improve the NOx− production rate at the first step. Further, CuCo2O4/Ni can also resolve the over bonding of the key intermediate of *NO, and thus reduce the energy barrier of the second step of eNOxRR. And finally, the “green” NH3 production achievs the excellent FENH3 (96.8%) and high‐record NH3 yield rate of 145.8 mg h−1 cm−2 with large partial current denstity (1384.7 mA cm−2). Moreover, an enlarged self‐made H‐type electrolyzer improves the NH3 yield to be 3.6 g h−1, and the obtained NH3 is then rapidly converted to a solid of magnesium ammonium phosphate hexahydrate, which favors the easy storage and transportation of NH3.This article is protected by copyright. All rights reserved