Efficient Ammonia Synthesis from Nitrate Catalyzed by Au/Cu with Enhanced Adsorption Ability

Abstract

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.