Theoretical Evidence On Pyridinic Nitrogen in N, S-Coordinated Co Single Atom Catalyst as Dominant Active Site Promoting H2 Cleavage, H Diffusion, and Hydrogenation Activity

Abstract

The isolated metal active sites in single atom catalysts (SAC) hinder their application in hydrogenation reactions, and the creation of additional active site beyond the metal site is a necessity. In this study, by introducing pyridinic N and S atoms into the N/C sheet, the local environment of Co site was optimally adjusted, synergistically boosting H2 activation, H diffusion, and the hydrogenation of nitrobenzene into aniline. The sterically hindered Co acidic site and N basic site (also known as frustrated Lewis pairs) in defect-containing Co-N3SN-def1 model cooperatively contribute to the highly efficient cleavage of the H2 molecule with a barrier of only 0.37 eV. The results support that the pyridinic N site in the Co-N3SN-def1 model serves as a reservoir for *H, mainly contributing to the enhanced activity for the hydrogenation of nitrobenzene. The mechanism revealed in this study provides insights into designing efficient heterogeneous catalysts for target hydrogenation reactions.

Keywords: Single Atom Catalyst, nitrobenzene hydrogenation, Density functional theory, frustrated Lewis pair, H dissociation