CeO₂纳米粉体的电化学制备及其形成机理初探

【作者】 杨文霞；

【导师】 潘湛昌；

【作者基本信息】 广东工业大学 ， 化学工艺， 2004， 硕士

【摘要】 本文主要采用电化学法制备了二氧化铈纳米粉末，通过X-衍射、透射电子显微镜等手段对所制备的纳米粒子进行了表征。 采用电化学法制备了均匀分散的CeO₂纳米粉体，经XRD和TEM分析，所制备的CeO₂粒子均属立方晶系，且呈球形。阴阳两极均生成CeO₂。提高溶液中氧气的浓度可使电流效率显著提高；电流密度越小，电流效率越高；溶液浓度也影响反应的电流效率。较佳的反应条件：Ce（NO₃）₃溶液浓度为0.5mol／L，加氨水保持溶液pH值在5.0，持续往电解液中通空气。 初步探讨了利用空气阴极，进行氧还原来制备二氧化铈超细粉体。通过X-衍射对产物进行了表征，并对制备工艺进行探讨。考察了反应的时间、电流密度、pH值对产量的影响。并与石墨作阴极的制备工艺作对比。通过实验得出最适宜反应条件：硝酸铈和硝酸铵的摩尔浓度均为0.5mol／L，电解的电流密度为0.025A／cm²。 采用线性扫描伏安法、循环伏安法在旋转圆盘电极上研究了氧气在Ce（NO₃）₃体系中的电化学性质。结果表明：O₂在电解过程中发生还原反应，导致电极表面pH值升高，为形成二氧化铈沉淀提供条件。在循环伏安研究中由加入体系中的H₂O₂进一步证明了O₂的还原作用。最后，通过旋转圆盘电极研究，确定O₂在Ce（NO₃）₃中近似按四电子步骤还原。更多还原

【Abstract】 Nanometer cerium(IV) oxide (CeO2) powder was prepared by means of electrochemical method. The powders were charactered through X-ray diffraction(XRD) and transmission electron micrograph(TEM). CeO2 powders in different ways and preparation technics were compared.Nanocrystalline CeO2 were prepared by means of electrochemical method. The powders were analyzed by using XRD and TEM. It showed that the synthesized CeO2 was cubic in structure and CeO2 particles were basically spherical in shape. CeO2 powder was formed at both cathode and anode.Current efficiency can be enhanced when the concentration of O2 in electrolyte is enhanced. The lower the current density, the higher the current efficiency. The current efficiency also change with the concentration of solution. From the experiment ,the better preparation condition is as follows: concentration of Ce(NO3)3 solution is 0.5 mol/L,value of pH is above 5.0 and there are enough O2.CeO2 powder was prepared using cerous nitrate and ammonium nitrate as raw material and air as cathode. Several factors, such as time, current density and pH were analyzed. The optimum preparation conditions are as follows: the concentration of cerous nitrate and ammonium nitrate is 0.5mol/L, and current density is 0.025A/ cm2.The electrochemical behavior of oxygen in the system of Ce(NO3)3 was studied by means of linear- voltammetry and cyclic-voltammetry. The results show that O2 is reduced on the electrode surface where the pH value grow up and CeO2 films form. The reduction of oxygen is proved further through adding H2O2 to the system of Ce(NO3)3 in cyclic-voltammetry study. According to rotating-disc electrode study, it is certain that O2 is reduced by four-electron-step in Ce(NO3)3 system.更多还原