Catalytic behavior of supported Ru nanoparticles on the {1 0 0}, {1 1 0}, and {1 1 1} facet of CeO2

•Ru0 at the metal–support interface facilitates the formation of oxygen vacancies on CeO2.•The oxygen vacancy concentration/type depends on the morphology/facet of CeO2.•Ru/CeO2-NCs{1 0 0} catalyst possesses the highest concentration of surface oxygen vacancy.•Ru/CeO2-NCs{1 0 0} catalyst exhibits the highest reaction rate toward CO2 methanation.•The surface oxygen vacancy in Ru/CeO2-NCs serves as the active site for CO2 activation.

The existence of oxygen vacancies in heterogeneous catalysis plays an essential role in determining the catalytic reactivity of metal catalysts. In this work, Ru nanoparticles were immobilized onto the CeO2 nanocubes (NCs), nanorods (NRs), and nanopolyhedrons (NPs) with the dominantly exposed {1 0 0}, {1 1 0}, and {1 1 1} facet of CeO2 support, respectively. Their catalytic behavior toward CO2 methanation was studied in detail, and the highest catalytic rate per gram of catalyst was obtained over the Ru(3%)/CeO2-NCs catalyst (reaction rate: 4.85 × 10−8 mol gcat−1 s−1; selectivity: 99%; 150 °C). The temperature-programmed reduction (TPR), Raman spectra, and oxygen storage capacity (OSC) test confirm that the Ru(3%)/CeO2-NCs catalyst possesses the highest concentration of oxygen vacancies owing to the Ru-promoted formation of oxygen vacancy on the CeO2-NCs. In addition, in situ infrared spectroscopy measurements demonstrate that the abundant oxygen vacancy in Ru(3%)/CeO2-NCs serves as the active site for CO2 activation, accounting for the significantly enhanced low-temperature reaction rate per gram of Ru/CeO2 catalyst.

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