First-principle molecular dynamics and in situ DRIFTS study the stability of the intermediates of CO2 hydrogenation to methanol on ZnZrOx solid solution catalyst

Abstract

Among the many catalysts used for CO2 hydrogenation to methanol, ZnZrOx solid solution is a highly efficient catalyst. Although the reaction mechanism has been widely explored at 0 K using DFT, critical aspects such as the atomic structure of the solid solution and the stability of reaction intermediates during CO2 reduction at experimental temperatures remain unclear. This study employs first-principle molecular dynamics (MD) simulations, FTIR and DRIFTS characterization to address these important questions. During the MD simulation, oxygen vacancies are formed in the system and same as the doped Zn atoms. The formation of oxygen vacancies was further confirmed by the Transmission FTIR and in situ DRIFTS. Due to the creating of oxygen vacancies, the coordination of Zn and Zr in the bulk is reduced to five and seven, respectively. And on the surface, their coordination is reduced to three、four and six、seven, respectively. Subsequently, the hydrogenation of CO2 to methanol using the formate and CO* pathways was studied. In the formate pathway, all intermediates remained stable at 593 K. However, in the CO* pathway, we observe instability of key intermediates which also confirmed by transmission FTIR and in situ DRIFTS characterization.