Activity of CeO2(111) supported Mnx(x = 1–6) for electrochemical N2 reduction reaction: Insights from density functional theory

It is challenging to realize an efficient nitrogen reduction reaction (NRR) under mild conditions, which suffers from low ammonia yield and low Faraday efficiency due to the extremely stable NN triple bond of N₂ as well as competitive hydrogen evolution reaction. In this work, the NRR reactivity of Mn_x(x = 1–6) clusters supported on CeO₂(111) (Mn_x(x = 1–6)/CeO₂(111)) was systematically investigated using density functional theory. A volcanic relationship between the limiting potential of NRR on Mn_x(x = 1–6)/CeO₂(111) and the atom number of Mn_x was found. Mn₃/CeO₂(111) shows the highest activity for NRR with a limiting potential of -0.36, -0.55 and -0.53 V along distal, alternating and enzymatic reaction pathway, respectively. Its high activity is attributed to the triangular geometry and optimal average number of electrons every Mn transferred from Mn₃ to CeO₂(111), which leads to the strong N₂ activation and the stabilization of nitrogen-containing intermediates. Also, Mn₃/CeO₂(111) exhibits a high NRR selectivity by hindering H adsorption and a high thermal stability at both 298 and 773 K, suggesting its promising potential as effective NRR catalyst. This work provides new insights into the rational design of single cluster catalysts.