Reaction-driven surface reconstruction of ZnAl2O4 boosts the methanol selectivity in CO2 catalytic hydrogenation

Identifying the surface structure of heterogeneous catalysts is critical for understanding the active sites, but it remains challenging due to the difficulty in characterizing the catalytic surfaces especially at elevated temperatures. Zn-based catalysts are high-efficiency alternatives for high-temperature methanol synthesis from CO2, as well as in bifunctional catalysts for hydrocarbons synthesis. Herein, the surface reconstruction of ZnAl2O4 spinel during CO2 hydrogenation reaction was investigated using detailed spectroscopic characterization. The results indicate that the reaction-driven surface reconstruction leads to the formation of amorphous ZnO on the ZnAl2O4 surface, which is accompanied by the increasing catalytic activity for methanol production. Kinetic analysis, STEM and in situ FTIR results indicate that the amorphous ZnO boosts the methanol formation rate by promoting the activation of H2. This study provides useful insight into the structure-activity relationship of zinc-based catalysts for CO2 hydrogenation and future design of new catalysts.