Enhanced thermal stability of Ce0.33Zr0.55(LaNdY)0.12O2 mixed oxides prepared by sulfate-aided coprecipitation method

• 作者: Shilei Chen Yongke Hou Hao Wang Zheng Zhao Yongqi Zhang Juanyu Yang Xiaowei Huang
• 来源期刊: 稀土学报（英文版）
• 年，卷（期）: 2021,（5）
• 所属期刊栏目: ADVANCED RARE EARTH MATERIALS
• 页码范围: 587-595
• 页数: 9页
• 语种: 英文

摘要

Ceria-zirconia based mixed oxides (CZs) have been applied in three-way catalysts (TWCs) for their high surface area and oxygen storage capacity (OSC). In this work, enhanced thermal stability of Ce0.33Zr0.55(LaNdY)0.12O2 mixed oxides was realized via a facile and scalable approach, namely, sulfate-aided coprecipitation method was labelled as CZ-S. Sulfate ion (SO2-4 ) was added into raw solution in the form of sulfuric acid and acted as coordination agent. The control sample was prepared by con-ventional coprecipitation method without sulfuric acid added and labelled as CZ. The promotion effect of sulfate ion was analyzed systematically by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), OSC and hydrogen temperature-programmed reduction (H2-TPR) analysis. XRD and high resolution TEM results reveal that CZ-S have homogeneous distributions of elements. TEM and SEM images show that fresh samples of CZ-S have narrower distributions of grain sizes and larger pore sizes than those of CZ. Through cross analysis of structure and morphology of CZ and CZ-S, we find that the introduction of sulfate ions results in uniform distributions of elements, narrows distributions of grain sizes, and enables the formation of secondary loose packing of sub-particles, which lead to enhanced thermal stability of the samples of CZ-S upon aging process at high temperature. After aging treatment at 1100 ℃ for 10 h, aged samples of CZ-S present larger specific surface areas and pore volumes than the aged sample prepared by conventional coprecipitation method without sulfate ions added. Furthermore, the aged sample of CZ-S2 (SO2-4 /Zr=1) possesses the highest specific surface area of 21.9 m2/g and the biggest pore volume of 0.035 mL/g among all aged samples.