O-doped graphdiyne as metal-free catalysts for nitrogen reduction reaction

Electrocatalytic nitrogen reduction reaction (NRR) is a sustainable and promising strategy for the conversion of N-2 into NH3. However, electrocatalytic NRR is vitally dependent on metal-based catalysts, and it remains a huge challenge in achieving effective NRR on metal-free catalysts. Here we report that O-doped graphdiyne (GDY) as a metal-free NRR electrocatalyst in aqueous solution. O doping in the GDY results in the redistribution of electron density, where the sp-C atom nearest to the O atom provides enhanced capture to N-2 molecules. The influence of surface strain on the progression of NRR on O-doped GDY surface has been investigated using the density functional theory (DFT) calculation method. The OFF calculations predict that the potential-limiting steps (PIS) do not vary with the strain, which is *NHNH2 ->*NH2NH2 for alternating mechanism and *NH2 ->*NH3 for distal mechanism wider the strain range of -1%similar to +5%; the limiting potentials of alternating mechanism is higher than that of distal mechanism; the limiting potentials of two mechanisms decrease with the tensile strain. It can be inferred that the NRR activity increases with a tensile strain of 0%similar to + 5%. Our study not only gets deep insights into the catalytic activity of O-doped GDY but also highlights the significance of strain engineering for catalyst design.