Knudsen Jan, Gallo Tamires, Boix Virgínia, Strømsheim Marie Døvre, D'Acunto Giulio, Goodwin Christopher, Wallander Harald, Zhu Suyun, Soldemo Markus, Lömker Patrick, Cavalca Filippo, Scardamaglia Mattia, Degerman David, Nilsson Anders, Amann Peter, Shavorskiy Andrey, Schnadt Joachim
Division of Synchrotron Radiation Research, Department of Physics, Lund University, Lund, Sweden.
MAX IV Laboratory, Lund University, Lund, Sweden.
Nat Commun. 2021 Oct 21;12(1):6117. doi: 10.1038/s41467-021-26372-y.
Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in their local gas environment, and the dynamics of the response is a decisive factor for the catalysts' action and activity. Few probes are able to map catalyst structure and local gas environment simultaneously under reaction conditions at the timescales of the dynamic changes. Here we use the CO oxidation reaction and a Pd(100) model catalyst to demonstrate how such studies can be performed by time-resolved ambient pressure photoelectron spectroscopy. Central elements of the method are cyclic gas pulsing and software-based event-averaging by image recognition of spectral features. A key finding is that at 3.2 mbar total pressure a metallic, predominantly CO-covered metallic surface turns highly active for a few seconds once the O:CO ratio becomes high enough to lift the CO poisoning effect before mass transport limitations triggers formation of a √5 oxide.
多相催化剂表面是动态实体，能对其局部气体环境的变化迅速做出响应，而这种响应的动力学是催化剂作用和活性的决定性因素。在动态变化的时间尺度下，很少有探针能够在反应条件下同时绘制催化剂结构和局部气体环境。在此，我们利用CO氧化反应和Pd(100)模型催化剂来展示如何通过时间分辨常压光电子能谱进行此类研究。该方法的核心要素是循环气体脉冲以及通过光谱特征的图像识别进行基于软件的事件平均。一个关键发现是，在总压力为3.2毫巴时，一旦O:CO比变得足够高以消除CO中毒效应，在传质限制引发√5氧化物形成之前，金属的、主要被CO覆盖的金属表面会在几秒钟内变得高度活跃。
