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.