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.

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Photo-thermochemical cycle (PTC) is a promising method to converting CO 2 to solar fuels. To study the mechanism of CO 2 reduction based on PTC, sol-gel synthesized titanium dioxide (ST) and Mn-doped TiO 2 (MT) films were produced and applied to the PTC under simulated solar light irradiation. Commercial P25 (PT) was used as a reference. Experiments show that Mndoped TiO 2 produced more CO than undoped TiO 2 and P25. The average CO production of 1.0 wt% MT by the PTC was 32.19 μmol⋅m À 2 ⋅h À 1 ), 4.36 times than that of ST and 3.63 times that of PT. Various characterization methods were conducted to investigated the effect of Mn ions doping on the photoresponse and charge transfer of samples. Density functional theory (DFT) calculations were also performed to verify the analysis and enhance the PTC mechanism. In conclusion, several key factors that Mn ions promote CO 2 conversion have been clarified.[a] B.

Solar-induced photothermal catalysis of the CO2 reduction reaction (CO2RR) is a promising method for chemical CO2 conversion. Modification of the metal oxide catalyst surface, including the introduction of oxygen vacancies and the doping and loading of metal or metal oxides, has a considerable influence on the product selectivity of the CO2RR. The complete free energy profiles of the CO2RR pathway on modified anatase TiO2 (101) surfaces are calculated based on density functional theory. The modified surfaces enhance the adsorption of CO2, and competition between desorption and reduction of the key intermediates (CO*, HCOOH*, HCHO*, and CH3OH*) is crucial to the selectivity for the CO2RR to form C1 products. The loading of Au and the doping of MgO enhance the electron transfer between the key intermediates and the surface, as well as the internal electron transfer inside the key intermediates, which efficiently activates the key intermediates and significantly increases the CH4 selectivity of the CO2RR.