Improving methanol selectivity in CO2 hydrogenation by tuning the distance of Cu on catalyst

It is desirable but challenging to obtain high methanol selectivity in CO2 hydrogenation on Cu/ZnO catalysts. Herein, we dispersed a commercial Cu/ZnO/Al2O3 on a silica support for CO2 hydrogenation to methanol, and discovered by high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM) that the distance between Cu nanoparticles on silica tuned the total methanol selectivity from 35.5 mol% to 88.9 mol%. This distance effect of Cu was elucidated by H2-TPR, FT-IR, in situ DRIFT, and catalyst silylation modification. It was identified that the active hydrogen species produced on Cu diffuse onto silica via the surface silanols, promoting reverse water gas shift (RWGS) reaction to produce CO. The average concentration of spilled hydrogen species was decreased along with the distance of Cu on silica, suppressing RWGS reaction and thus highlighting methanol selectivity. We anticipate that the distance effect observed here is prevalent on metal supported catalysts in other (de)hydrogenation reactions.