Surface Engineering Division, CSIR-National Aerospace Laboratories, Bengaluru 560017, India.
Department of Chemistry, Jadavpur University, Kolkata 700032, India.
J Nanosci Nanotechnol. 2021 Mar 1;21(3):1641-1652. doi: 10.1166/jnn.2021.18988.
Cerium oxide particles with different morphologies, namely nanoparticles, nanofibers, nanocubes, and rice grains have been prepared by simple chemical routes. The shape and size of the synthesized morphologies have been studied using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). X-ray diffraction (XRD) and selected area electron diffraction (SAED) techniques have been used to determine their crystal phases. Both nanoparticles and nanocubes of cerium oxide exclusively crystallize in fluorite structure of CeO₂ as observed in XRD patterns, whereas nanofibers and rice grains are characterized by the presence of CeO₂, Ce₂O₃, and Ce(OH)₃ phases. X-ray photoelectron spectroscopy (XPS) has been employed to evaluate Ce species present in the different cerium oxide morphologies and to estimate their relative surface concentrations. As evident from Ce 3d core level spectra cerium oxide nanoparticles and nanocubes are basically CeO₂ having Ce in the +4 oxidation state along with some amount of Ce species. In contrast, Ce is in +3 oxidation state on its surface in cerium oxide nanofibers and rice grains that contain intermediate phases like Ce₂O₃ and Ce(OH)₃ as endorsed by XRD patterns. CO oxidation has been carried out over these cerium oxide morphologies and among all morphologies lowest temperature CO oxidation has been demonstrated by the nanocube morphology.
已通过简单的化学途径制备了具有不同形态的氧化铈颗粒，即纳米颗粒、纳米纤维、纳米立方体和稻米粒。使用场发射扫描电子显微镜（FESEM）和透射电子显微镜（TEM）研究了合成形态的形状和尺寸。X 射线衍射（XRD）和选区电子衍射（SAED）技术用于确定它们的晶体相。氧化铈的纳米颗粒和纳米立方体仅在 XRD 图谱中观察到以萤石结构形式结晶的 CeO₂，而纳米纤维和稻米粒的特征在于存在 CeO₂、Ce₂O₃和 Ce(OH)₃相。X 射线光电子能谱（XPS）用于评估不同氧化铈形态中存在的 Ce 物种，并估算它们的相对表面浓度。从 Ce 3d 芯能级谱可以看出，氧化铈纳米颗粒和纳米立方体基本上是 CeO₂，Ce 处于+4 氧化态，同时存在一定量的 Ce 物种。相比之下，氧化铈纳米纤维和稻米粒中的 Ce 处于表面的+3 氧化态，这一点得到了 XRD 图谱的支持，因为这些纤维和稻米粒中含有中间相，如 Ce₂O₃和 Ce(OH)₃。对这些氧化铈形态进行了 CO 氧化反应，在所有形态中，纳米立方体形态表现出最低的 CO 氧化温度。
