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.