Unveiling the nature of glucose hydrogenation over Raney Ni: DFT and AIMD simulations

Glucose hydrogenation to sorbitol is a vital industrial reaction for the utilization of biomass. Generally, hydrogenation is catalyzed by the inexpensive Raney Ni catalyst which has good catalytic but suffers from poor stability and side reaction，and the mechanisms of glucose hydrogenation on Raney Ni surfaces is also unclear. This study combines density functional theory calculations, ab initio molecular dynamics simulations (AIMD), and experiments to reveal the nature of glucose hydrogenation on the (111), (200), and (220) surfaces of Ni catalyst. The DFT calculation results show that the (111) and (200) surfaces of Raney Ni are favorable for hydrogenation with 111-η2, 200-η2–1, 200-η2–3 adsorption configurations and adsorption energy is closely related to the rate-determining step. Furthermore, in-situ IR analysis and AIMD calculation confirm the existence of 111-η2 structure in hydrogenation, while electronic analysis demonstrates that improving the alignment of the nickel surface's d orbitals with the -CO bond's π orbitals can enhance both the adsorption and catalytic hydrogenation activity. In addition, the (220) surface is found to be responsible for the dehydrogenation of cyclic-glucose, and decreasing the percentage of the (220) surface and increasing the reaction temperature appropriately may be effective in inhibiting the side reaction. This paper not only reveals the nature of Raney Ni catalyzed glucose hydrogenation but also lights the direction for the design of highly efficient nickel-based catalysts.