Study on the Effect and Mechanism of Pt and Au noble metal loading on TiO2 Catalysts for CO2 Photo-Thermal Reduction

Herein, Pt/TiO2 and Au/TiO2 catalysts were synthesized by photodeposition method, and CO2 photothermal reduction performance, physicochemical characterization, photochemical characterization and in situ mechanism experiments were performed on catalysts with different Pt and Au loading ratios. The results showed that the loading of Pt and Au can effectively enhance the optical absorption characteristics of TiO2, which is due to the strong metal–semiconductor interaction and the plasmon resonance effect on the surface of noble metal nanoparticles. PT-0.4 and AT-2 had a relatively stronger photochemical absorption and conversion ability. In addition, the load of Pt mainly enhances the selective conversion to CH4, while the load of Au mainly enhances the selective conversion to CO. However, Pt nanoparticles are prone to noble metal agglomeration, which reduces the catalytic activity, while Au nanoparticles are relatively stable. Mechanism study showed that PT-0.4 and AT-2 catalysts have similar intermediate species in the dark adsorption and light reaction stages, but PT-0.4 mainly achieves CH4 generation through intermediate species such as *CHO, while the key species of CO generation on the surface of AT-2 is mainly *COOH.