A novel photo-thermochemical cycle for the dissociation of CO2 using solar energy

To dissociate carbon dioxide (CO2) using solar energy, a novel photo-thermochemical cycle combining photochemistry with thermochemistry is proposed in this paper. After illuminating titanium dioxide (TiO2) in a helium (He) atmosphere by ultraviolet (UV) irradiation, CO2 was input and converted to carbon monoxide (CO) under heating in an enclosed cavity. To determine the optimal heating temperature, sets of four consecutive cycles were performed at temperatures from 573 K to 873 K. The preferred temperature was found to be 773 K. CO was stably produced in five successive cycles at 773 K, demonstrating the method's possibility. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were employed to assess the crystal structure and morphology. X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) analyses were also conducted to investigate the charge transfer and reaction mechanisms on the TiO2 surface. Finally, a charge transfer mechanism is tentatively proposed.