Tuning product selectivity of CO2 hydrogenation by OH groups on Pt/γ-AlOOH and Pt/γ-Al2O3 catalysts

Abstract

Herein, we explore how OH groups on Pt/γ-AlOOH and Pt/γ-Al2O3 catalysts affect CO2 hydrogenation with H2 at temperatures from 250°C to 400°C. OH groups are abundant on γ-AlOOH, but rare at Pt-(γ-AlOOH) interface which is the most favorable site for CO2 conversion on Pt/γ-AlOOH. This makes CO2 hydrogenation on Pt/γ-AlOOH form CO weakly bonding to γ-AlOOH, which prefers to desorption from Pt/γ-AlOOH rather than further conversion, thus enhancing CO production on Pt/γ-AlOOH. Different from Pt/γ-AlOOH, OH groups are abundant at Pt-(γ-Al2O3) interface which is the most favorable site for CO2 conversion on Pt/γ-Al2O3. This promotes CO2 hydrogenation on Pt/γ-Al2O3 to form CO strongly bonding to Pt, which prefers to further hydrogenation to CH4, and thereby increases CH4 selectivity on Pt/γ-Al2O3. Therefore, the OH groups at metal-support interface are crucial factor influencing product distribution, and must be considered seriously when fabricating catalysts.