The VN3 embedded graphane with the improved selectivity for nitrogen fixation

Abstract

The N2 electrochemical reduction reaction (NRR) under ambient conditions is vital for the sustainable energy utilization. Herein, the NRR performances of the VN3 anchored graphene, graphane and fluorographene are systematically investigated via density functional theory calculations. Our results reveal that the VN3 embedded graphene exhibits the superior activity through an enzymatic mechanism with an onset potential of 0.28 V. The graphene hydrogenation significantly depresses the competitive hydrogen evolution reaction (HER) and remarkably improves the NRR selectivity. Conversely, the graphene fluorination results into the worsening of the NRR selectivity, which rules out VN3 decorated fluorographene as the NRR electrocatalyst. Moreover, the thermodynamic decomposition potentials of the N elements are 0.20 and 0.07 V for the supports of graphene and graphane, respectively, indicating that no stability deterioration is occurred by hydrogenation. The electronic structures analysis uncovers that the substrate is the electron reservoir for the charge transfers meanwhile the VN3 moiety acts as a bridge to link the substrate and adsorbates, which provides the explanation for the influence of the substrate on the NRR performance. The finding provides a rational strategy to design functional carbon-based electrocatalysts.