Screening transition metal and nonmetal atoms co-doped graphyne as efficient single-atom catalysts for nitrogen reduction

Despite the great potential of electrocatalytic nitrogen reduction reaction (NRR) for more sustainable and energy-efficient ammonia (NH3) production, significant challenges remain, including low activity and poor selectivity of currently available catalysts. In this study, we systematically investigate the electrocatalytic NRR performance of 43 types of single-atom catalysts (SACs) constructed by introducing single transition metal (TM) or/and nonmetal (NM) atoms in graphyne (TM-NM-GY) through first-principles calculations. It is found that Mn-, Os-, B-, Ti-B-, V-B-, Cr-B-, Ru-B-, and Os-B-GY exhibit remarkable efficiency for NRR, showcasing overpotentials lower than 0.34 V. Particularly, Os-B-GY stands out by demonstrating ultra-high catalytic activity, selectivity, and stability for NRR as well as good experimental feasibility, with an impressively low overpotential of merely 0.13 V. The co-doping of Os and B allows for adjusting moderately positive charge densities around Os, which enables strong d-2π* coupling between Os and N2. As a result, the NN triple bond is remarkably weakened, facilitating the subsequent NRR process. Moreover, benefiting from the cooperative doping of NM and TM, the potential limiting step is changed, which breaks the inherent linear volcanic relationship between the free energy of the critical intermediate N2H* and limiting potential (UL) on the sole TM-doped system, further enhancing the activity and selectivity. We anticipate that the insights gained from this comprehensive and systematic study can offer valuable guidance for the design and synthesis of novel and highly efficient SACs toward NRR.