N and O multi-coordinated vanadium single atom with enhanced oxygen reduction activity.

Recently, atomically dispersed transition-metal single atom in nitrogen-doped carbon matrix as electrocatalysts has aroused general interest. However, there is no report about vanadium single atom for ORR in the literature. According to d-band center theory for transition-metals, the performance of catalysts is regulated by the electronic structure of the catalytic center which determines the intermediate adsorption kinetics. Indeed, the valence of vanadium is variable, its electron structure could be modulated by an appropriate coordination structure. Here, a novel method is developed to prepare the N and O co-coordinated vanadium single atom (V-N1O4) embedded in the carbon matrix. The catalyst displays a half-wave potential of 865 mV in base solution which surpasses 20% Pt/C, and also shows a high power density of 180 mW/cm2 in Zn-air batteries. DFT calculations reveal that the N and O coordination configuration could regulate the electron structure and geometry of vanadium to boost the electrocatalytic activity.