Photo-thermal conversion of CO2 and biomass-based glycerol into glycerol carbonate over Co3O4-ZnO p-n heterojunction catalysts

Transforming CO2 and biomass-based glycerol into glycerol carbonate is an economical and green process. However, this reaction is thermodynamically unfavorable. Breaking the thermodynamic limitation is the key to accelerate the reaction. In this study, a photo-thermal catalytic system was established and a series of low-cost xCo3O4-ZnO p-n heterojunction catalysts were prepared. It was discovered that 20%Co3O4-ZnO gave the best photo-thermal performance, recording a glycerol carbonate yield of 5.3% under the conditions of 0.50 g catalyst, 10 mmol glycerol, 5 MPa CO2, 20 mL DMF, reaction time 6 h, 150 °C and a 225 W visible light irradiation. Both light and heat were regarded to contribute to the photo-thermal catalytic system. Under thermal-driven conditions, the performance of xCo3O4-ZnO was influenced significantly by the strength and quantity of basic sites on catalyst surface, while the visible light harvesting capacity as well as the electron-hole separation and migration efficiency were crucial for their activity enhancements under light irradiation. This study is predicted to provide an avenue to construct photo-thermal catalysts for glycerol conversion reactions.