A first-principles study of transition metal clusters supported on graphene as electrocatalysts for N2 to NH3 reaction

NH3 is an important raw material for a variety of chemicals, but also an important carbon-free energy carrier. Currently, NH3 synthesis mainly relies on Habor–Bosch method with high energy consumption, high pollution and low efficiency. So it is urgent to develop a green process for NH3 synthesis. The electrochemical NH3 synthesis can be carried out under ambient conditions. Therefore, it is very important to find electrocatalysts with good stability, high activity and excellent selectivity. Here, we have designed homonuclear transition metal (TM = Fe, Co, Ni) clusters catalyst supported on graphene (TM3 @Gra) as electrocatalysts for nitrogen reduction reaction (NRR). The mechanism of electrocatalytic NRR on TM3 @Gra was investigated. The Fe3 @Gra, Co3 @Gra, and Ni3 @Gra showed high catalytic activity with corresponding limiting potential of –0.60, –0.64 and −0.45 V, respectively. Finally, the selectivity and thermal stability analysis confirmed that TM3 @Gra were the ideal NRR electrocatalysts. We hope that the results of this study will facilitate the design and development of NRR catalysts and provide theoretical reference for the rational design of cluster catalysts.