Investigating the catalytic activity of Mgn (n = 4–8) clusters for the hydrogen evolution reaction using density functional theory

To efficiently desorb H₂, pure Mg_n (n = 4–8) clusters were chosen for the hydrogen evolution reaction with H₂O. At the PBE0/def2-TZVP level and the PBE0-D3/def2-TZVP level, the lowest energy structures of Mg_n (n = 4–8) clusters and the most stable structures of Mg_n@H₂O (n = 4–8) complexes were searched in the local region. The transition state was predicted, and then the hydrogen evolution reaction channel was obtained by using the intrinsic reaction coordinate (IRC) to confirm the transition state. To better analyze the hydrogen reaction mechanism, the character of Mg_n@H₂O (n = 4–8) complexes and Mg_nO (n = 4–8) clusters, as well as the atomic charge change trend, were investigated using interaction region indicator function analysis (IRI) and natural population analysis (NPA). The reaction effect of Mg₄ cluster and H₂O is the worst. The energy barrier does, however, progressively lower as the cluster atom count rises, improving the reaction effect.