Revealing and Regulating the Complex Reaction Mechanism of CO2 Hydrogenation to Higher Alcohols on Multifunctional Tandem Catalysts

Abstract

Revealing and regulating the intricate reaction mechanism of direct CO2 hydrogenation to higher alcohols (C2+OH), especially for the crucial C–C coupling step, is still a great challenge. Herein, the specific reaction network on Co2C and CuZnAl multifunctional tandem catalysts is elucidated by designing subtly surface adsorption–desorption reactions, in situ chemical transient kinetics, and theory calculations. The key C–C coupling step for the formation of C2+OH over the sole Co2C catalyst was the insertion of CO into R-CHx, while the reaction mechanism can be modulated to the coupling of R-CH2 and CHO with a lower energy barrier on the tandem catalyst (Co2C||CuZnAl). R-CH2 was derived from the hydrogenation dissociation of olefins and coupled with the CHO from formate hydrogenation at the Cu/ZnAl2O4 interface. Such multifunctional tandem catalysts exhibited a high space–time yield of C2+OH of 2.2 mmol g–1 h–1. This work provides an effective strategy for studying complex mechanisms, contributing to the precise design of highly efficient catalysts and the optimization of reaction pathways.