Photothermal Coupling Factor Achieving CO2 Reduction Based on Palladium-Nanoparticle-Loaded TiO2

Solar fuels have attracted great interest as an alternative use for solar energy. However, the challenges are high temperatures and low solar utilization for thermochemical and photochemical conversion methods, respectively. To lower the temperature in thermochemistry and increase solar energy utilization, a photothermochemical cycle (PTC) has been reported for carbon dioxide (CO2) reduction and improved by palladium-nanoparticle-loaded TiO2 (PNT). A maximum and stable carbon monoxide (CO) production of 11.05 μmol/(h g) is demonstrated using 1.0PNT, which is 8.27× the CO produced by P25 in the PTC. The PNT can enhance light utilization by a red-shifted photoresponse range and visible light absorbance of localized surface plasmon resonances (LSPRs). Photoinduced electron and hole pairs (EHPs) could be more readily separated. More available charge carriers would induce more photoinduced vacancies in the photoreaction, which serve a key role in the PTC. Additionally, Pd can promote CO2 absorbance to form Pd-CO2– and Pd-CO2–-VO on the defective surface in the thermal reaction. Finally, CO production can be enhanced by a photothermal coupling factor, and a reaction mechanism is proposed for the complete cycle on the basis of both theoretical calculations and experiments.