Synthesis, Characterization, and Thermochemical Redox Performance of Hf4+, Zr4+, and Sc3+ Doped Ceria for Splitting CO2

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• 作者：Jonathan R. Scheffe ; Roger Jacot ; Greta R. Patzke ; Aldo Steinfeld
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：November 21, 2013
• 年：2013
• 卷：117
• 期：46
• 页码：24104-24114
• 全文大小：664K
• 年卷期：v.117,no.46(November 21, 2013)
• ISSN：1932-7455

文摘

We present results on the thermochemical redox performance and analytical characterization of Hf⁴⁺, Zr⁴⁺, and Sc³⁺ doped ceria solutions synthesized via a sol鈥揼el technique, all of which have recently been shown to be promising for splitting CO₂. Dopant concentrations ranging from 5 to 15 mol % have been investigated and thermally cycled at reduction temperatures of 1773 K and oxidation temperatures ranging from 873 to 1073 K by thermogravimetry. The degree of reduction of Hf and Zr doped materials is substantially higher than those of pure ceria and Sc doped ceria and increases with dopant concentration. Overall, 10 mol % Hf doped ceria results in the largest CO yields per mole of oxide (0.5 mass % versus 0.35 mass % for pure ceria) based on measured mass changes during oxidation. However, these yields were largely influenced by their rate of reoxidation, not necessarily thermodynamic limitations, as equilibrium was not achieved for either Hf or Zr doped samples after 45 min exposure to CO₂ at all oxidation temperatures. Additionally, sample preparation and grain size strongly affected the oxidation rates and subsequent yields, resulting in slightly decreasing yields as the samples were cycled up to 10 times. X-ray diffraction, Raman, FT-IR, and UV/vis spectroscopy in combination with SEM-EDX have been applied to characterize the elemental, crystalline, and morphological attributes before and after redox reactions.