A theoretical study for methanol synthesis by CO2 hydrogenation

Ab initio MO calculations were carried out using the density functional method for the reaction intermediate of methanol synthesis by CO2 hydrogenation. The energy change of the bridging-formate due to changing the Cu-Cu interatomic distance showed that the formate intermediate was formed at the neighboring Cu atoms and no significant difference was found in the stability of the copper crystal surface. The stability of the methanol synthesis intermediates with the atomic charge of Cu was also calculated. The stability of the formate and the formaldehyde intermediates increased as the total charge increased. The stability of the methoxy species was almost constant between a total charge of 0 to +0.4. There seems to be an appropriate value for the charge of the surface copper. On the other hand, the reverse water-gas shift reaction producing carbon monoxide occurred on the metallic copper. The calculation of the total atomic charge distributions on Cu/CuO and Cu/ZnO clusters showed that the cationic copper was located only on the boundary of Cu and the oxide. The number of active sites increased as much as the degree of dispersion of Cu and the oxide, and a high-performance catalyst is expected to be designed in such a manner.