上海科技大学知识管理系统

In this work, we constructed the low Miller index surfaces of (100), (001), (111), and (110) of the ZnGa2O4 spinel catalyst. Through extensive DFT calculations, we found that the oxygen vacancy (VO) formation energies on the (100) and (001) surfaces were <1.0 eV, whereas those on the (111) and (110) surfaces were >3.0 eV. We further examined the dissociation of molecular hydrogen (H2) on these surfaces, and found that H2 homolytic dissociation tended to occur on surfaces with lower VO formation energies, while H2 heterolytic dissociation were favored on those with higher VO formation energies. CO2 adsorption and activation on the different surfaces of the ZnGa2O4 spinel catalyst were investigated, and on surfaces with lower VO formation energies, CO2 adsorbs in a linear configuration (ln-CO2*), while on surfaces with higher VO formation energies, CO2 adopts in a bent adsorption geometry (bt-CO2*) and is easier to dissociate. For HCOO formation from ln-CO2* + H*, the (110) surface has the lowest energy barrier, so it is likely the most active surface for CO2 hydrogenation to methanol (CH3OH). Thus, we compared the CH3OH formation pathway on the ZnGa2O4(110) surface with the pathways for direct and indirect CO2 dissociation, and predicted it to favor CH3OH production. Our calculations reveal the active surfaces of the ZnGa2O4 spinel catalyst for CO2 hydrogenation to CH3OH, and provide insights into the experimentally observed high CH3OH selectivity, which should be important for the rational design of Zn-based spinel catalysts for this reaction.