Photothermal catalytic processes are of great significance for efficiently utilizing solar energy to catalyze the reactions of transforming cheap raw materials to high value-added chemicals. Transforming CO2 and biomass-based glycerol, which is by-product from the biodiesel manufacturing, into high value-added glycerol carbonate is a green and promising approach for simultaneously utilizing CO2 and glycerol. However, the reaction of CO2 and glycerol to produce glycerol carbonate is thermodynamically unfavorable for thermal catalysis. Breaking the thermodynamic limitation is the key to effectively utilizing this process. Introducing abundant solar energy into a thermal-driven reaction system can effectively activate reactants, break through the thermodynamic limitation, increase catalytic rate, and enhance the selectivity of target products.

In this work, we have developed Co3O4-ZnO and Au/Co3O4-ZnO catalytic materials with photothermal synergistic function, and introduced solar energy into the reaction system for the synthesis of glycerol carbonate from CO2 and glycerol. A series of Co3O4-ZnO and Au/Co3O4-ZnO catalysts were prepared by hydrothermal and impregnation methods. The photo-thermal catalytic reactions were carried out in a 100 mL stainless-steel autoclave.

The results of characterizations and reactions showed that the cooperation between Co3O4 and ZnO exerted significant functions on the catalytic activities for transforming CO2 and glycerol to glycerol carbonate, light irradiation further improved their catalytic performance because of the photo-thermal synergistic effect. Meanwhile, the heterojunction structure of p-n type semiconductor Co3O4-ZnO and the localized surface plasmon resonance of Au nano-particles improved visible light absorption capacity and electron-hole separation efficiency. The separated electrons and holes activated CO2 and glycerol, respectively, which played dominant roles for catalytic performance improvement under visible light irradiation. 

Dehua HE graduated from East China University of Science and Technology (Jan. 1982). He received Master degree from Okayama University of Japan (March 1987) and obtained his Ph.D. degree from Tokyo Institute of Technology of Japan (March 1990), followed by the research works at Sagami Chemical Research Center of Japan (1991-1994). He has joined Tsinghua University since 1995. He is interested in heterogeneous catalysis.