Controlled Synthesis, Characterization, and Morphology-Dependent Reducibility of Ceria—Zirconia—Yttria Solid Solutions with Nanorod-like, Microspherical, Microbowknot-like, and Micro-octahedral Shapes

摘要

By adopting the strategy of triblock copolymer (Pluronic P123) or cetyltrimethylammonium bromide (СТАВ) assisted hydrothermal treatment, we fabricated cubic fluorite-type Ce_0.6Zr_0.3Y_0.1O_2 (CZY) solid solution polycrystallites with various morphologies. These materials were characterized by means of techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, X-ray photoelectron spectroscopy, thermogravimetry, laser Raman, Fourier-transfer infrared spectroscopy, hydrogen temperature-programmed reduction, and surface area measurements. It .is found that the nanorod-like, microspherical, microbowknot-like, and micro-octahedral CZY particles were respectively generated hydrothermally with CTAB at 120 °C for 72 h and with P123 at 100, 120, and 240 °C for 48 h after calcination at 550 °C for 3 h. There was a copresence of Ce~3+ and Ce~4+ in the CZY samples that led to the formation of oxygen vacancies. We observed a good correlation of low-temperature reducibility with the morphology of the CZY samples. The reducibility of these nano- and micromaterials at low temperatures (240-550 °C) enhanced in the order micro-octahedral CZY < microspherical CZY < microbowknot-like CZY < nanorod-like CZY. The formation mechanism of CZY with various morphologies was discussed.