Effect of Structure of CeOHCO3 Precursor of CeO2 on Its Catalytic Performance

A modified hydrothermal process method based on using urea instead of water as the solvent was used to prepare CeOHCO3. Pure CeOHCO3 with a single crystalline structure was produced by varying the experimental conditions. CeO2 particles obtained from these CeOHCO3 precursors were tested for CH4 oxidation. The temperatures for 90% methane conversion were 604 and 647°C for CeO2 catalysts obtained from hexagonal and orthorhombic CeOHCO3, respectively, indicating that the CeO2 catalyst from hexagonal CeOHCO3 (CeO2-A) was more active than that from the orthorhombic form (CeO2-D). The specific surface area and pore volume of CeO2-A were 45 m2/g and 0.35 cm3/g, respectively, which were higher than those of CeO2-D. H2-TPR showed a much lower reduction temperature and enhanced reducibility with CeO2-A. XPS and O2-TPD results demonstrated there were more oxygen vacancies on the surface of CeO2-A than on CeO2-D, which implied increased oxygen mobility. The CeOHCO3-structure dependent activity was investigated and found to originate from the morphologies of the CeOHCO3 precursors. Hexagonal CeOHCO3 had a rod-like shape while orthorhombic CeOHCO3 had a sphere-like morphology. After calcination, the obtained CeO2 had the morphology of the precursor. The difference in morphology gave CeO2 catalysts with different texture, structure, reducibility, and thus catalytic activity.

摘要采用一种快速、无模板、低成本的微波辅助水热法在 2 min 内制备了三维花状 Co3O4. 所用原料均是无机盐. 前驱体浓度和尿素的逐渐水解对 Co3O4 形貌影响很大. 制得的花状 Co3O4 比表面积大, 且暴露了 (110) 高活性指数面, 对 CO 氧化具有较高的催化活性.

The properties and catalytic activity of CeO2 are closely related to the structure of CeOHCO3 precursor. CeO2 nanorods derived from hexagonal CeOHCO3 have high activity than those from orthorhombic CeOHCO3.Figure optionsDownload as PowerPoint slide