Theoretical insight into the mechanism of Li-mediated nitrogen reduction reaction by density functional theory

Lithium-mediated electrochemical nitrogen reduction reaction (NRR) as an alternative to the Haber-Bosch process has attracted increasing attention because of its high faradaic efficiency and reproducibility. However, the limited understanding of the mechanism has hampered further improvement of its catalytic performance. This work has endeavored to study the process of Li-mediated NRR and its underlying mechanism using density functional theory. It is founded that the Li₆N₂, Li₇N₂ atom groups, Li₃N (001) and Li₃N (110) layer stably exist on the deposited Li (001) layer. The replacing model has been established to describe the hydrogenation process with ethanol as a proton source, revealing that the replacement between Li and H atom is a spontaneously thermal process. Based on the replacing mechanism, the structure of interface and coverage rate of reactive sites are the two main factors that determine the ammonia formation. These findings further our understanding of Li-mediated NRR mechanism and will be helpful for the rational design of experiments of Li-mediated NRR.