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

[Display omitted] • Two structures (Sc–V Li−LiH and Mo–V Li−LiH) and original LiH were constructed for NRR by DFT. • Both Sc–V Li−LiH and Mo–V Li−LiH have excellent stability and electron activity. • The adsorption of N 2 by Sc and Mo atoms is significantly enhanced after doping. • The effective charge transfer of Sc–V Li−LiH and Mo–V Li−LiH can fully activate N 2. • Mo–V Li−LiH has higher NRR activity than Sc–V Li−LiH due to lower energy barrier of rate-determining step. 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–V Li−LiH) and Mo (Mo–V Li−LiH). The doping of monatomic Sc and Mo can effectively transfer and activate the electrons in the material to N 2 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 N 2. For Sc–V Li−LiH , the most potential path of NRR is the alternating mechanism, in which the rate-determining step is the formation of *NH 2 −*NH 2 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–V Li−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–V Li−LiH. [ABSTRACT FROM AUTHOR]