Morphology dependence of catalytic properties of Ni/CeO2 for CO2 methanation: A kinetic and mechanism study

Abstract

• Ceria nanorods (NR) and nanocubes (NC) are prepared with hydrothermal method. • Ni/CeO 2 -NR holds a higher number of Ce 3+ proportion compared with Ni/CeO 2 -NC. • Ni/CeO 2 -NR shows a higher activity than Ni/CeO 2 –NC. • CO 2 methanation on Ni/CeO 2 goes through a formate route. • The oxygen vacancy are active sites for the formate formation. Ceria has been used for catalyst support for long time due to its unique structural properties resulting from oxygen vacancies and reversible valence change (Ce 4+ and Ce 3+ ). In this report, ceria nanorods (NR) and nanocubs (NC) were prepared with hydrothermal method and 5 wt% nickel was loaded on it. The effect of morphology of ceria supports for CO 2 methanation reaction was studied. Characterization including TPR, TEM, XRD and XPS shows that Ni/CeO 2 -NR had a higher number of Ce 3+ proportion compared with Ni/CeO 2 -NC. Both catalysts showed high conversion and selectivity for methane at low temperature range at200–250 °C and interestingly Ni/CeO 2 -NR exhibited a higher activity than Ni/CeO 2 –NC. A kinetic study and DRIFTs investigation were carried out to formulate the mechanism. It turned out that CO 2 methanation on Ni/CeO 2 goes through a formate route instead of CO 2 dissociation and the oxygen vacant sites are supposed to be the active sites for the formate formation in this mechanism.