The Role of Mo Single Atoms and Clusters in Enhancing Pt Catalyst for Benzene Hydrogenation: Distinguishing Between Benzene Spillover and Electronic Effect

Reactant spillover and electronic effects are two indistinguishable factors that influence MoO₃ promoters in benzene hydrogenation on Pt-MoO₃ catalysts. Previous studies have primarily focused on the significance of hydrogen spillover while neglecting the transfer of benzene and the electronic effect originating from MoO₃. Herein, we synthesized Pt/CNT, Pt-Mo₁/CNT with Mo single atoms, and Pt-Mo_cluster/CNT with MoO_x cluster promoters by using atomic layer deposition. The catalyst Pt-Mo₁/CNT exhibited higher activity (3361.8 h^-1) in benzene hydrogenation at 50 °C, which was twice as high as that of Pt/CNT. In contrast, the presence of closely interacting MoO_x clusters with Pt nanoparticles inhibited the activity of the Pt catalyst. Kinetic experiments, DFT calculations, in situ FTIR, and AIMD simulations revealed that Mo single atoms on multiwalled carbon nanotubes did not alter the structure or electronic state of Pt nanoparticles but enhanced their activity by increasing benzene coverage via benzene spillover. On the other hand, although the hydrogen and benzene coverage increased with MoO_x cluster promoters, changes in the electronic state of Pt nanoparticles resulted in a higher energy barrier for the rate-determining step.