Mechanism of CO2 hydrogenation to methanol on the W-doped Rh(111) surface unveiled by first-principles calculation

Understanding the mechanisms of CO2 hydrogenation on a specific catalyst is of profound significance for developing the high-efficient catalytic materials. Herein, first-principles calculation is performed to research the mechanisms of methanol synthesis from CO2 hydrogenation on tungsten (W)-doped Rh(111) catalyst. The optimal adsorption site, geometric parameters, and adsorption energy of each species are determined. The analysis of electronic structure reveals that CO2* is greatly activated on the W-doped Rh(111) surface due to the charge transfer and obvious orbital hybridization between them. Then, a descriptor is defined to preliminarily predict the reaction thermodynamics. Furthermore, the optimal reaction mechanism is determined by comparing the activation barriers and reaction energies of all elementary reactions. Compared with Rh(111), it can be found that the doping of W has a great hindrance to the elementary reactions in the RWGS and trans-COOH pathways, while the elementary reactions of the HCOO pathway are less affected. The optimal hydrogenation route on the W-doped Rh(111) surface is the HCOO pathway followed by CO2* -> HCOO* -> HCOOH* -> H2COOH* -> H2CO* -> CH3O* -> CH3OH*. The analysis of Mulliken charge shows that after the doping of W atoms, the modified electronic structure of Rh(111) is conducive to the conversion of CO2 and the generation of CH3OH.