Metal-Free C3N4 with plentiful nitrogen vacancy and increased specific surface area for electrocatalytic nitrogen reduction

As a substitute for synthetic ammonia under mild condition, electrocatalytic nitrogen reduction reaction (NRR) provides a hopeful approach for the development of ammonia. Nevertheless, the current development of NRR electrocatalysts is far from enough and a systematic research is needed to gain a better improvement. This article presents that 2D C3N4-NV with a large specific surface area and abundant nitrogen vacancies is prepared by a simple and feasible method, and used as a metal-free catalyst for electrocatalytic NRR. Experiment result and density functional theory (DFT) calculation reveal that nitrogen vacancies in 2D C3N4-NV can act as an efficient active site for catalytic NRR, which is conducive to capturing and activating N2, lowering Gibbs free energy (ΔG) in reaction and inhibiting hydrogen evolution reaction (HER) at the same time. In addition, the larger specific surface area also makes more active site exposed, which is good for the contact between the electrolyte and the active site, thus enhancing its NRR activity. The electrocatalyst shows an excellent catalytic activity for NRR in 0.1 M HCl, including Faradaic efficiency of 10.96%, NH3 yields of 17.85 μg h−1mgcat.−1, and good stability (over 20 h).