DFT insights into the hydrodesulfurization mechanism over the Fe, Ni or Cu-substituted ReS2 active phases

Abstract

This research investigated the reaction mechanisms over the different M-doped (M = Fe, Ni and Cu) ReS₂ (100) surfaces for the hydrodesulfurization (HDS) of thiophene via the density functional theory (DFT) calculations. The calculation results showed that the electronic structure (especially the d-orbital) and the geometric structure (S-M-S bond angle) of the doped metals significantly affected the adsorption energies of thiophene. The adsorption energies followed the order of Fe-ReS₂ > Ni-ReS₂ > Cu-ReS₂. Additionally, it could be found that the σ adsorption mode was more stable than the π mode. Bader charge and PDOS analyses indicated that the strongest electronic interaction and orbital hybridization existed between the Fe-ReS₂ and thiophene, which could effectively weaken the C-S bond. Further calculations of the reaction pathway revealed that Fe-ReS₂ exhibited excellent adsorption and activation capabilities for both thiophene and H₂ (with a co-adsorption energy of -1.18 eV). The reaction barrier of the hydrogenation pathway was 1.02 eV, which was lower than that of the direct desulfurization pathway (1.67 eV), making it more thermodynamically favorable. This research provided theoretical insights for the design of high-efficiency transition metal sulfide-based HDS catalysts.