Effect of External Electric Field on Nitrogen Activation on a Trimetal Cluster.

Efficient nitrogen (N 2 ) fixation and activation under mild conditions are crucial for modern society. External electric fields (F electric ) can significantly affect N 2 activation. In this work, the effect of F electric on N 2 activation by Nb 3 clusters supported in a sumanene bowl was studied by density functional theory calculations. Four typical systems at different stages of N-N activation were studied, including two intermediates and two transition states. The impact of F electric on various properties related to N 2 activation was investigated, including the N-N bond length, overlap population density of states (OPDOS), total energy of the system, adsorption energy of N 2 , decomposition of energy changes, and electron transfer. The sumanene not only functions as a support and protective substrate, but also serves as a donor or acceptor under different F electric conditions. Negative F electric is beneficial to N-N bond activation because it promotes electron transfer to the N-N region and improves the d-π* orbital hybridization between metals and N 2 in the activation process. Positive F electric improves d-π* orbital hybridization only when the N-N is nearly dissociated. The microscopic mechanism of F electric 's effects provides insight into N 2 activation and theoretical guidance for the design of catalytic reaction conditions for nitrogen reduction reactions (NRR).