Theoretical study on structural properties and mechanism of nitrogen reduction of monatomic Sc and Mo doped Li defect LiH

Abstract

In this work, density functional theory (DFT) was used to calculate the structure, charge transfer and electrocatalytic nitrogen reduction reaction (NRR) catalytic activity of Li-defected lithium hydride (LiH) by doping monatomic transition metal Sc (Sc–VLi−LiH) and Mo (Mo–VLi−LiH). The doping of monatomic Sc and Mo can effectively transfer and activate the electrons in the material to N2 molecule. The Gibbs free energy study of the reaction path shows that the doped system can effectively reduce the free energy of NRR reaction and improve the hydrogenation reaction capacity of N2. For Sc–VLi−LiH, the most potential path of NRR is the alternating mechanism, in which the rate-determining step is the formation of *NH2−*NH2 with an reaction free energy of 1.326 eV, and the reaction free energy of the formation of *NNH in the initial reaction is only 0.235 eV. Mo–VLi−LiH tends to perform NRR by distal mechanism, and the reaction free energy of rate-determining step is only 0.714 eV, which has lower reaction free energy and higher catalytic activity than Sc–VLi−LiH.