Photothermocatalysis provides a green approach to convert solar energy to chemical energy. In previous studies, the most catalysts were powdered particles, which faces a problem that the light irradiation cannot reach the underlying catalysts, thereby making these catalysts not exhibit activity. A possible resolution to this difficulty is to load active phase on a thin substrate. In this study, a photothermocatalytic film of Ru/quartz filter paper (abbreviated as QFP) was designed, in which the Ru particles were loaded on a QFP with a thickness as thin as 0.36 mm. A photothermal synthesis was adopted to load the Ru particles. A 5 μL of precursor of RuCl₃ ethanol solution was dripped on the QFP and then the QFP was dried under the irradiation of Xe lamp; this operation was repeated until all the precursor were loaded. After that, the QFP with Ru precursor was reduced in an atmosphere of H₂/Ar mixture [V(H₂)∶V(Ar)=1∶9] at photothermal 400 ℃ for 30 min. The loading mass of Ru particles were optimized by loading 1, 2, 3, and 4 mg of Ru on QFP to fabricate four samples. The X-ray diffraction (XRD) measurement revealed that the QFP was amorphous while the loaded Ru particles were metallic. The scanning electronic microscopy (SEM) indicated that the Ru particles were loaded on the SiO₂ fiber of QFP steadily and most of Ru particles possessed a size less than 200 nm. Next, the photothermocatalytic CO₂ methanation was carried out over the as-prepared catalysts to assess their catalytic activity. The catalyst with 2 mg Ru loading showed the highest performance; it delivered an 85.5% of CO₂ conversion during 2 h of light irradiation. Although the four samples exhibited different CO₂ conversion, the selectivities for CH₄ product over these samples were all close to 100%. The stability of optimal catalyst was tested in a flow-type reaction system; under a 5 mL•min^－1 flow rate of reactant gases, the CO₂ conversion over the catalyst could remain around 51% during 12 h and the apparent CH₄ yield rate reached 478.1 mmol•g_Ru^－1•h^－1. This study demonstrates a photothermal synthesis of recyclable Ru/QFP film and its application of photothermocatalytic CO₂ methanation, which provides an energy-efficient process to achieve decarbonization and therefore is of great potential for practical application.

Key words: photothermocatalysis, Ru, quartz filter paper, CO₂ methanation, photothermocatalytic film