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

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.