Figure 11 . H2-TPR profile of MnO2-H-200 at different ozone conversion (1, 0.6 and 0.2)
In order to further confirm the influence of the accumulation of O2*on the catalysts, the structures of MnO2-H-200 before and after reaction were analyzed by XRD as shown in Figure 12. The diffraction peaks of the reacted catalysts corresponded well to the standard PDF card (JCPDS 72-1984) of MnO2 and no extra impurities were observed, which indicated that the accumulation of O2*had slight effect on the catalyst crystal structure or the changes were too trivial to detect.