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

The Ru/CeO 2 samples were prepared with loading Ru nanoparticles onto three different shapes (nanocubes, rods, and polyhedrons) of the CeO 2 surface and evaluated for catalytic performances in CO 2 methanation under visible light or not. It was found that the cube-like Ru/CeO 2 sample (Ru/CeO 2 -c) exhibited a visible light-enhanced catalytic performance, but an insignificant photopromoted activity occurred on rod- or polyhedron-like Ru/CeO 2 samples (Ru/CeO 2 -r or Ru/CeO 2 -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/CeO 2 under illumination were caused by the different metal–support interaction forces. The strong interaction formed in Ru/CeO 2 -c could promote the photoexcited electrons from cube-like CeO 2 to transfer onto the Ru surface, which accelerated the generation of oxygen vacancies in Ru/CeO 2 -c. On the contrary, a weak interaction occurred on Ru/CeO 2 -r and Ru/CeO 2 -p samples. In this case, the photoexcited electrons would hardly transfer onto the Ru surface, and no more oxygen vacancies were generated on Ru/CeO 2 -r and Ru/CeO 2 -p, resulting in a negligible photopromoted activity.