微纳尺度壳核结构氧化铈合成与构效关系研究

The nanoscale ceria-based material attracted worldwide attentions because of its special properties, but its application is always limited by its poor hydrothermal stability. Based on our previous results, a core-shells structure ceria with micro and nanoscale show superior anti-sintering ability, this can be prepared by ceria nanocrystalline granulation, pore-creating to form porous micron level grains, building shell take porous micron level grains as the core. In this project, the controllable preparation and the structure-activity relationship will be investigated. To optimize the nanoscale ceria preparation technology, spray granulation technology, granule pore-creating technology and deposition building shell technology, the controllable preparation of core-shells structure ceria with micro and nanoscale will be realized. The qualitative and quantitative characterization methods will be established for the core-shell structure sample. The relationship between the microstructure parameter (such as crystalline surface, interface and defects etc) and the effect of micro and nanoscale and the effect of core-shells structure will be clarified. The kinetic equation of oxygen storage/release capacity and correction model of grain cementation for CeO2 will be established. The influence and kinetics of material structure on the oxygen vacancy formation and migration will be investigated. The structure-activity relationship between the effect of micro and nanoscale and the effect of core-shells structure with hydrothermal stability and dynamic oxygen storage/release capacity will be clarified. The work is important to develop the new type, effective rare earth catalyst, and helpful to further the nano catalysis theory.

纳米尺度铈基材料表现出优异的催化性能而备受关注，但高温水热稳定性差是制约其广泛应用的世界难题。申请者前期研究发现通过对纳米CeO2晶粒造粒/造孔形成多孔微米级颗粒，并造壳得到的微纳尺度壳核结构氧化铈具有优异的抗烧结能力。本课题针对微纳尺度壳核结构CeO2的可控制备及构效关系而展开，通过纳米级氧化铈制备技术、喷雾造粒技术、颗粒造孔技术及沉积造壳技术等工艺优化，实现微纳尺度壳核结构CeO2可控制备；建立微纳尺度壳核结构CeO2三维结构定性定量描述方法；阐明晶面、晶界及缺陷等微观结构参数与微纳尺寸效应、壳核结构效应协同控制晶体生长的基本原理，构建微纳尺度壳核结构CeO2晶粒烧结修正模型；考察材料结构对氧空位形成/迁移影响规律与动力学行为，明确微纳尺寸效应、壳核结构效应与材料高温水热稳定性及动态储放氧性能之间的构效关系，为新型高效稀土催化剂研究开发、发展纳米催化理论提供理论依据。

纳米尺度铈基材料表现出优异的催化性能而备受关注，但高温水热稳定性差是制约其广泛应用的世界难题。本课题研究内容包括1）微纳尺度核壳结构铈基材料合成；2）微纳尺度核壳结构铈基材料构效关系研究；3）贵金属（过渡金属）与铈基氧化物相互作用研究。通过纳米级氧化铈制备技术、喷雾造粒技术、颗粒造孔技术及沉积造壳技术等工艺优化，实现微纳尺度壳核结构铈基材料的可控制备；研究发现通过对纳米CeO2晶粒造粒/造孔形成多孔微米级颗粒，并造壳得到的微纳尺度壳核结构铈基材料具有优异的抗烧结能力。研究发现，晶化处理降低了氧化铈表面氧空位浓度降低，并形成无序化晶界；长时间晶化处理削弱了Pt-CeO2相互作用，导致储放氧过程活化能明显提高。采用自行修正的活化能可变型抛物线模型分析老化过程中晶体生长情况，结果表明随着晶化处理时间的延长，晶体生长表观活化能从120~140 kJ/mol增加到200 kJ/mol），该活化能数值上与红外漫反射光谱（DRIFTS）中位错型晶界吸收峰的能量状态具有显著的线性关系，证明位错型晶界的生成是纳米氧化铈稳定性提高的主要原因。