Photothermal Synthesis of Glycerol Carbonate <i>via</i> Glycerol Carbonylation with CO<sub>2</sub> over Au/Co<sub>3</sub>O<sub>4</sub>-ZnO Catalyst

Glycerol carbonylation with CO2 to synthesize glycerol carbonate is a promising approach for CO2 utilization.This reaction can be achieved through a thermally-driven catalytic pathway, but it is constrained by thermodynamic equilibrium.In the present study, we introduced solar energy into the reaction system to enable a photo-thermal synergistic catalytic reaction, breaking through the thermodynamic limitations.We developed a series of xAu/20Co3O4-ZnO catalysts, where Co3O4-ZnO, a composite of p-type semiconductor Co3O4 and n-type semi-conductor ZnO, exhibited a heterojunction structure, and Au nanoparticles loaded onto the surface of Co3O4-ZnO revealed the localized surface plasmon resonance (LSPR).We investigated the ability of xAu/Co3O4-ZnO to absorb visible light absorption, the efficiency of separating photo-generated hole-electron pairs, and the impact of Au on the photothermal synergistic catalytic performances of Au/Co3O4-ZnO catalysts.We also examined the effects of Au doping on the bulk and surface properties, including crystalline structures, morphologies, specific surface areas and pore structures, the binding energies of the elements, surface acid-base sites, and reduction behaviors of xAu/Co3O4-ZnO.Our findings revealed that the heterojunction structure of Au/20Co3O4-ZnO facilitated visible light absorption and hole-electron pair separation.The size of Au nano-particles (NPs) loaded on Co3O4-ZnO surface was approximately 50 nm.The loading of Au altered the electron density of Co and Zn, improved the reducibility of Co species, and enhanced the presence of oxygen vacancies on Co3O4-ZnO surface.The LSPR of Au NPs further enhanced the visible light absorption capacity of Au/20Co3O4-ZnO, and improved the separating of photogenerated hole-electron pairs, thus enhancing the photothermal catalytic performances.With the optimizing conditions (150 °C, 5 MPa, 6 h, and 225 W visible light irradiation), the 2%Au/20Co3O4-ZnO catalyst demonstrated excellent performances, yielding a glycerol carbonate yield of 6.5%.This study is expected to serve as a reference for the rational design of improved photothermal catalysts for glycerol carbonylation with CO2 to produce glycerol carbonate in the future.