Structural Evolution and Catalytic Activity of ZnO-ZrO2 Catalysts: A Temperature-Dependent XRD Study

ZnO-ZrO2 samples calcined at temperatures ranging from 350 ﾰC to 450 ﾰC for a duration of 4 hours were analyzed using XRD (X-ray diffraction). The XRD pattern, as shown in Fig. 11, revealed that the ZnO/ZrO2 catalyst primarily existed in a hexagonal phase. No characteristic signal value corresponding to the ZnO crystal phase was observed, suggesting that ZnO was highly dispersed on the surface of ZrO2 or incorporated into its pores within the examined temperature range. Consequently, a solid solution of ZnO/ZrO2 was formed (Guidi et al., 2003).

As the calcination temperature increased from 350 ﾰC to 450 ﾰC, the intensity of the characteristic signal value increased, while the peak width decreased and the peak shape gradually sharpened. These observations imply that the integrity of the grain and crystal shape can influence the characteristic signal value of the catalyst. By correlating the experimental findings on crystal integrity with the catalytic activity, it was observed that a higher value of catalytic activity corresponded to greater crystalline integrity of the catalyst.

Upon reaching a calcination temperature of 400 ﾰC, the formation of the ZnZrO phase was confirmed by comparing it with the standards in the card library. This finding suggests that ZnO and ZrO2 were connected through Zn-Zr-O bonds in the catalyst structure.