Nitrogen-doped graphdiyne for efficient electrocatalytic N2 reduction: A first-principles study

Electrocatalytic fixation of N2 has attracted intensive attention as an alternative for the Harbor–Bosh technique. In this work, the activity of N-doped graphdiyne (GDY) for electrochemical N2 reduction reaction (NRR) was investigated with density functional theory. Four different models were considered, namely the Graph-N, sp-N-1, sp-N-2, and pyridinic-N GDY. Electronic structure analysis reveals that N-doing increases the positive charges on adjacent carbon atoms, which greatly promotes the adsorption and activation of N2. The sp-N-2 GDY is the most active one among the substitutionally doped models with a limiting potential of −0.99 V. For pyridinic-N GDY, NRR follows a Mars–van Krevelen (MvK) pathway with a limiting-potential of −1.22 V. More importantly, we found that Graph-C vacancy created in the MvK path can efficiently reduce N2 with a low limiting-potential of −0.41 V via a hybrid pathway. Besides, the selectivity for NRR over hydrogen evolution reaction is also enhanced on sp-N-2 GDY and the defective GDY with Graph-C vacancy. This work provides a comprehensive understanding of the activity and selectivity of N-doped GDY and suggests that the sp-N-2 and pyridinic-N doping greatly enhance the performance of GDY for NRR.