The effect of H O on the total oxidation
As listed in Table 2, the Ea values of the Sn-rich catalysts were lower than that of the SnO2, and the Sn0.7Ce0.3O2 catalyst had the lowest Ea value. Interestingly, the Ea values decreased following the lowered reduction temperatures of the surface Sn4+ in Fig. 8. It confirms that upon the Sn-rich catalysts Ea is directly linked to the reducibility of the surface Sn4+ cations, and the surface Sn4+ cations are active sites for methane combustion.