Rothensteiner Matthäus, Sala Simone, Bonk Alexander, Vogt Ulrich, Emerich Hermann, van Bokhoven Jeroen A
Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
Phys Chem Chem Phys. 2015 Oct 28;17(40):26988-96. doi: 10.1039/c5cp03179f.
X-ray absorption spectroscopy was used to characterise ceria-based materials under realistic conditions present in a reactor for solar thermochemical two-step water and carbon dioxide splitting. A setup suitable for in situ measurements in transmission mode at the cerium K edge from room temperature up to 1773 K is presented. Time-resolved X-ray absorption near-edge structure (XANES) data, collected for a 10 mol% hafnium-doped ceria sample (Ce0.9Hf0.1O2-δ) during reduction at 1773 K in a flow of inert gas and during re-oxidation by CO2 at 1073 K, enables the quantitative determination of the non-stoichiometry δ of the fluorite-type structure. XANES analysis suggests the formation of the hexagonal Ce2O3 phase upon reduction in 2% hydrogen/helium at 1773 K. We discuss the experimental limitations and possibilities of high-temperature in situ XAS at edges of lower energy as well as the importance of the technique for understanding and improving the properties of ceria-based oxygen storage materials for thermochemical solar energy conversion.
利用X射线吸收光谱对基于二氧化铈的材料进行表征，这些材料处于太阳能热化学两步水和二氧化碳分解反应器中的实际条件下。本文介绍了一种适用于在室温至1773 K范围内，在铈K边以透射模式进行原位测量的装置。在1773 K的惰性气体流中对10 mol% 铪掺杂二氧化铈样品（Ce0.9Hf0.1O2-δ）进行还原过程中，以及在1073 K下用CO2进行再氧化过程中收集的时间分辨X射线吸收近边结构（XANES）数据，能够定量测定萤石型结构的非化学计量比δ。XANES分析表明，在1773 K的2%氢气/氦气中还原时会形成六方Ce2O3相。我们讨论了在较低能量边进行高温原位XAS的实验局限性和可能性，以及该技术对于理解和改善用于热化学太阳能转换的基于二氧化铈的储氧材料性能的重要性。
