The teams of Xiao Jianping and Wang Guoxiong at the CAS Dalian Institute of Chemical Physics, Chinese Academy of Sciences have made progress in the study of ammonia synthesis by electrocatalytic nitric oxide reduction and achieved 96.9% of ammonia Faraday efficiency and Ampere current density on a Cu6Sn5 alloy catalyst. Electrochemical synthesis of ammonia is a greener and more economical strategy for decentralized ammonia synthesis compared to the traditional Haber method.
In their study, Xiao Jianping’s team initially screened copper-tin alloys with high eNORR ammonia synthesis activity through a descriptor-based approach based on self-developed graph theory and reaction phase diagram analysis algorithms. Wang Guoxiong’s team further synthesized Cu6Sn5 alloy and verified that it has amperometric ammonia synthesis activity. Nitric oxide electrocatalytic experiments showed that the Cu6Sn5 catalyst has higher activity and selectivity than Cu and Sn, exhibits high ammonia synthesis selectivity over a wider voltage range, and maintains stable operation for 135 h at >600 mAcm-2. Electrochemical energy barrier calculations show that the Cu6Sn5 catalyst generates ammonia at a lower energy barrier than on Cu and Sn, and it is demonstrated that the relationship between the magnitude of the decisional rate-step energy barriers for each product on the Cu6Sn5 alloy is in line with the trend of the experimentally measured product FE distribution.
The rate of ammonia production by nitric oxide electroreduction on Cu6Sn5 alloy reaches 2.5 molh-1 at a total current of 400 A, demonstrating the potential for application.