## 4 Conclusions  
In this work, various CeO\({}_{2}\) catalysts with three different morphologies, i.e., irregular nanoparticles, nanorods, and nanocubes, were synthesized via a modified preparation method, and they were investigated for their thermocatalytic performance in DMMP decomposition. Based on the results, the as-prepared CeO\({}_{2}\) nanorods exhibited superior MSTC as compared to the irregular CeO\({}_{2}\) nanoparticles and nanocubes. For the CeO\({}_{2}\) nanomaterials with the same morphology, i.e., 12 MCeO\({}_{2}\)nr and 6 MCeO\({}_{2}\)nr, it is noted that 12 MCeO\({}_{2}\)nr with larger crystal sizes exhibited higher protection time, MSTC, and SSTC than 6 MCeO\({}_{2}\)nr with smaller crystal sizes. This same conclusion exists for CeO\({}_{2}\) nanocubes. These results indicated that the morphologies and crystal sizes of the CeO\({}_{2}\) nanomaterial could significantly affect the catalytic performance. The various CeO\({}_{2}\) nanomaterials with different morphologies and particle sizes possessed different redox activity (H\({}_{2}-\)TPR), surface oxygen species (XPS), relative oxygen vacancy concentration (Raman), and the ability of the catalyst to resist poisoning. However, these properties did not show direct relationships with the catalytic performance of the material, which indicates that the catalytic performance of CeO\({}_{2}\) nanomaterials is not only affected by a single factor, instead it may be a result of a set of factors, and it will be an interesting work in our future study. It is speculated that the change in the Ce\({}^{3+}\) content before and after the protection test could be due to the poisoning of the catalyst, therefore affecting the protection time. Based on the storage and release characteristics of CeO\({}_{2}\), the catalytic decomposition of DMMP was performed through the cyclic process that involved the consumption of surface lattice oxygen and adsorbed oxygen, and the timely replenishment of bulk and external oxygen. The main reaction path of the catalytic DMMP decomposition was similar for all three morphologies samples, the gas products were methanol, CO, H\({}_{2}\), CO\({}_{2}\), and H\({}_{2}\)O, and the surface byproduct was phosphates. However, during the side reaction that involved methanol, the reaction paths of three morphologies samples are different. On the surface of CeO\({}_{2}\) irregular nanoparticles, carbonate and formate were produced, while formate and possibly carbonate were produced on the surface of CeO\({}_{2}\) nanorods, only carbonate was formed on the surface CeO\({}_{2}\) nanocubes. The CeO\({}_{2}\) catalyst was inactivated due to the accumulation of phosphorus oxygen species and carbon oxygen species on the surface of CeO\({}_{2}\). Thus, based on the collective results, a basic understanding of the catalytic DMMP decomposition based on CeO\({}_{2}\) with different morphologies was attained, and this understanding will contribute to the future design and preparation of high-performing catalysts for the degradation of chemical toxicants.  
**Author Contributions:** [PERSON] completed the main experimental work and wrote the initial draft; [PERSON], [PERSON] and [PERSON] assisted in data collection; [PERSON], [PERSON] and [PERSON] provided evolution of overarching research goals and revised pre-publication stages as the corresponding author. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was financially supported by the National Natural Science Foundation of China (No. 21701186) and the Fundamental Research Funds from State Key Laboratory of NBC Protection for Civilian (SKLNBC 2019\(-\)04), China.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.