Thermoresistive catalytic combustion sensors based on noble metals are very stable stable and highly sensitive devices to monitor potentially explosive atmospheres. We studied and proved the high stability of rhodium oxide-based sensors under working conditions in different CH₄/air mixtures (up to 3.5 vol % methane) with the help of operando X-ray-based characterization techniques, DC resistance measurements, and IR thermography using a specially designed in situ cell. Operando X-ray diffraction and X-ray absorption spectroscopy showed that the active Rh species are in the oxidized state and their chemical state is preserved during operation under realistic conditions. The resistance correlated with the surface temperature of the pellistor and is related to the combustion of CH₄, confirming the catalytic nature of the observed sensing process. Only under harsh operation conditions such as an oxygen-free atmosphere or enhanced working current, a reduction in the active Rh₂O₃ phase was observed. Finally, the effect of poisoning causing the lowered activity on the catalytic combustion of methane was investigated. While stable rhodium sulfate might form in a sulfur-poisoned pellistor, silicon dioxide seems to additionally physically block the pores in the alumina ceramics of the pellistor poisoned by hexamethyldisiloxane.

中文翻译：

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通过Operando X射线吸收光谱和X射线衍射证明，基于Rh氧化物的热阻催化燃烧传感器具有很高的稳定性。

基于贵金属的热阻催化燃烧传感器是非常稳定，稳定和高度敏感的设备，可监控潜在的爆炸性气氛。我们借助于基于X射线的表征技术，直流电阻测量和红外技术，研究并证明了基于氧化铑的传感器在不同CH ₄ /空气混合物（甲烷含量最高为3.5 vol％）的工作条件下的高稳定性。使用专门设计的原位电池进行热成像。OperandoX射线衍射和X射线吸收光谱表明，活性Rh物质处于氧化状态，并且在实际条件下的操作过程中保留了它们的化学状态。电阻与薄膜晶体管的表面温度相关，并且与CH ₄的燃烧相关，从而确认了观察到的传感过程的催化性质。仅在苛刻的操作条件下，例如无氧气氛或增强的工作电流，活性Rh ₂ O ₃才会降低观察到相。最后，研究了中毒引起活性降低对甲烷催化燃烧的影响。尽管稳定的硫酸铑可能会在硫中毒的薄膜中形成，但二氧化硅似乎会物理上堵塞被六甲基二硅氧烷所污染的薄膜的氧化铝陶瓷中的孔。