Thermal Methanol Synthesis from CO2 Using Cu/ZnO Catalysts: Insights from First-Principles Calculations

Catalytic hydrogenation of carbon dioxide to methanol offers a promising avenue for recycling CO2, enhancing environmental sustainability. Cu/ZnO has long been identified as one of the most effective heterogeneous catalysts for this reaction, yet the detailed understanding of its reaction mechanism and active sites remains incomplete. Recent advances have highlighted the critical role of defects, such as ZnCu steps and stacking faults on Cu surfaces, in enhancing catalyst performance. Here this concept is explored through first-principles surface simulations of six models, featuring diverse Cu-Zn combinations and specific coordination environments under realistic conditions. It is revealed that Cu/ZnO catalysts with kink defects, rather than surface ZnCu alloys, exhibit optimal activity for methanol synthesis. Specifically, the findings demonstrate how intermediate configurations and rate-determining steps vary with changes in surface structure and reveal the role of the kink in promoting CO2 reduction to methanol through electronic structure calculation. Moreover, it is found that the predominant synthetic pathway for CH3OH from CO2 involves the reverse water gas shift and CO hydrogenation, rather than the formate route, on Cu/ZnO surfaces with kinks.