Graphdiyne/main-group metal elements sandwich structure as a promising single atom electrocatalyst for nitrogen reduction: A theoretical investigation

In an effort to limit global warming and CO2 emission, ammonia has become a viable hydrogen carrier and alternative fuel. Electrocatalytic nitrogen reduction (e-NRR) has gained much attention as a mean to produce ammonia under mild reaction conditions. Consequently, the advancement of highly efficient and selective catalysts for e-NRR is key in the development of clean energy. Based on the "chainmail" protection catalyst proposed by recent studies, we used first-principles calculations to design a catalyst composed of a single main-group metal atom sandwiched between BN-doped graphdiyne and graphdiyne sheets. The structures, labeled BN-M-G (M = Li, Na, K, Mg, Ca and Al), were investigated as potential catalysts for e-NRR. After screening the most favorable configurations for N2 adsorption and activation, we further explored their e-NRR catalytic properties including efficiency and selectivity. Our results show that the optimal e-NRR path on BN-Mg-G and BN-Al-G is the alternating path with a limiting voltage of -0.47 V and -0.67 V, respectively. In contrast to the competing reaction, hydrogen evolution reaction (HER), both catalysts show high selectivity towards e-NRR. Our work shows that through rational design and electronic structure regulation, main-group-metals-based catalysts can have comparable catalytic activity as transition metal catalysts. This present study offers new insights for the development of low-cost and environmetally-friendly main group metal catalysts.