Superior catalytic activity of a Pd catalyst in methane combustion by fine-tuning the phase of ceria-zirconia support

Methane, one of the greenhouse gases, is controlled by the catalytic combustion that is the most efficient method. Herein, ceria-zirconia solid solutions (CeZrO4) with high specific surface areas and different phases (kappa appa and tetragonal) were synthesized and then used to construct the supported Pd catalyst for methane combustion. Compared to the tetragonal CeZrO4 support (t-CZ), the smaller particle sizes of PdOx and the higher amount of active PdO species are present on the kappa appa CeZrO4 support (kappa-CZ), leading to a higher ability of the Pd/kappa-CZ catalyst for methane activation. More critically, the oxygen mobility of the Pd/t-CZ catalyst is much higher than that of the Pd/t-CZ catalyst. Consequently, an excellent and stable redox cycle of PdO species is achieved on the Pd/kappa-CZ catalyst compared to the Pd/t-CZ catalyst, prompting the oxidation of hydrocarbon fragments. These two factors result into a superior catalytic activity of the Pd/kappa-CZ catalyst for methane combustion.