Photothermal-Catalyzing CO2 Methanation over Different-Shaped CeO2-Based Ru Nanoparticles

The Ru/CeO2 samples were prepared with loading Ru nanoparticles onto three different shapes (nanocubes, rods, and polyhedrons) of the CeO2 surface and evaluated for catalytic performances in CO2 methanation under visible light or not. It was found that the cube-like Ru/CeO2 sample (Ru/CeO2-c) exhibited a visible light-enhanced catalytic performance, but an insignificant photopromoted activity occurred on rod- or polyhedron-like Ru/CeO2 samples (Ru/CeO2-r or Ru/CeO2-p). The detailed catalytic mechanism was monitored by temperature-programmed reduction, X-ray photoelectron spectroscopy, and electron paramagnetic resonance. It was proposed that the different photoassist activities of Ru/CeO2 under illumination were caused by the different metal–support interaction forces. The strong interaction formed in Ru/CeO2-c could promote the photoexcited electrons from cube-like CeO2 to transfer onto the Ru surface, which accelerated the generation of oxygen vacancies in Ru/CeO2-c. On the contrary, a weak interaction occurred on Ru/CeO2-r and Ru/CeO2-p samples. In this case, the photoexcited electrons would hardly transfer onto the Ru surface, and no more oxygen vacancies were generated on Ru/CeO2-r and Ru/CeO2-p, resulting in a negligible photopromoted activity.