Röhrens Daniel, Abouserie Ahed, Dalfollo Gianluca, Kahlert Jannis, Wang Bangfen, Schönberger Ariel Augusto, Pischinger Stefan, Chen Peirong, Mueller David N, Simon Ulrich
Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, Aachen, 52074, Germany.
Chair of Thermodynamics of Mobile Energy Conversion Systems, RWTH Aachen University, Forckenbeckstraße 4, Aachen 52074, Germany.
ACS Appl Mater Interfaces. 2024 Dec 11;16(49):67662-67673. doi: 10.1021/acsami.4c13212. Epub 2024 Nov 26.
As a model for the energy-efficient aftertreatment of exhaust gas components, we studied microwave-assisted (MW) CO oxidation over a (La,Sr)CoO (LSC) perovskite oxide catalyst under dry and humidified conditions. We found that the use of a MW-based process can offer multiple advantages over traditional thermocatalysis in this scenario, as the nature of the MW-solid interaction offers quick, adaptive, and energy-efficient heating as well as improved yield and lower light-off temperatures. As found by combined CO and water MW-desorption experiments, the presence of technically relevant amounts of water leads to a competition for surface active sites and thus slows the reaction rate without indications for a fundamental change in the mechanism. Remarkably, the performance loss related to the presence of water was less pronounced in the MW-assisted process. Additionally, while we recorded a temperature-dependent degradation of the reaction rate in extended MW-catalysis experiments both in dry and humidified conditions, it quickly recovered after a short reactivation MW-treatment. Our study confirms that surface reaction can be driven by the use of MW-radiation in a similar magnitude that can be achieved by thermal activation at significantly higher temperatures. The nature of the effect of the MW-treatment on the structural and electronic surface properties of the LSC material was investigated by X-ray absorption (XAS) and X-ray photoelectron spectroscopy (XPS). We found evidence of a significant structural, chemical, and electronic reorganization of the oxide surface, possibly consistent with the occurrence of overheated surfaces or "hotspots" during MW-exposure, which may explain the increased catalytic and heating properties of the LSC after the MW-pretreatment. The good catalytic performance, quick response to MW-heating, and long-term stability of the catalyst all indicate the promising potential of a MW-based process for the energy-efficient exhaust aftertreatment using noble-metal-free oxide catalysts.
作为废气成分节能后处理的模型，我们研究了在干燥和加湿条件下，微波辅助（MW）的一氧化碳（CO）在（镧，锶）钴氧化物（LSC）钙钛矿氧化物催化剂上的氧化反应。我们发现，在这种情况下，与传统热催化相比，基于微波的工艺具有多种优势，因为微波与固体相互作用的性质提供了快速、自适应且节能的加热方式，同时提高了产率并降低了起燃温度。通过CO和水的微波脱附联合实验发现，技术上相关量的水的存在会导致对表面活性位点的竞争，从而减慢反应速率，但未表明反应机理有根本性变化。值得注意的是，在微波辅助过程中，与水的存在相关的性能损失不太明显。此外，虽然我们在干燥和加湿条件下的扩展微波催化实验中都记录到了反应速率随温度的下降，但在短时间的再活化微波处理后，反应速率迅速恢复。我们的研究证实，微波辐射可以驱动表面反应，其程度与在显著更高温度下通过热活化所能达到的程度相似。通过X射线吸收（XAS）和X射线光电子能谱（XPS）研究了微波处理对LSC材料结构和电子表面性质的影响。我们发现了氧化物表面发生显著结构、化学和电子重组的证据，这可能与微波照射期间过热表面或“热点”的出现一致，这可以解释微波预处理后LSC催化和加热性能的提高。催化剂良好的催化性能、对微波加热的快速响应以及长期稳定性都表明，基于微波的工艺在使用无贵金属氧化物催化剂进行节能废气后处理方面具有广阔的应用前景。
