Iwanek Nee Wilczkowska Ewa M, Liotta Leonarda Francesca, Pantaleo Giuseppe, Hu Linje, Williams Shazam, Kirk Donald W, Kaszkur Zbigniew
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
Istituto per lo Studio di Materiali Nanostrutturati (ISMN)-CNR, Palermo I-90146, Italy.
ACS Mater Au. 2024 Sep 24;4(6):643-653. doi: 10.1021/acsmaterialsau.4c00062. eCollection 2024 Nov 13.
Herein, we present a paper that attempts to bridge the gap between CO oxidation catalytic tests performed in a model stream and a more realistic exhaust gas stream by incorporating characterization methods that allow for active probing of the catalyst surface. The results have shown that it is not just the abundance of a given type of species on the surface that impacts the activity of a system but also the ease of extraction of ions from their surface (time-of-flight secondary ion mass spectrometry) and the response of the support to change in the feed composition (dynamic in situ X-ray diffraction (XRD) with variable atmosphere). The study utilizes the method of doping a catalyst (RuO/CZ) with a small amount of alkali-metal (K or Na) carbonates in order to slightly modify its surface to gain insight into parameters that may cause discrepancies between model stream activity and complex stream activity. The most pronounced difference is that in the model stream, which contains only CO and O in helium, both alkali ions improve the activity of the system at temperatures around 175 °C, whereas in the complex stream, which mimics the exhaust stream from a diesel engine under oxygen lean conditions, the K-doped catalyst is slightly worse than RuO /CZ and RuO + Na/CZ and much worse in propane combustion. The total hydrogen consumption values (temperature-programmed reduction) and the O/O ratios (X-ray photoelectron spectroscopy) both place the RuO + K/CZ system between the other two and hence provided no reason for the unusual behavior of the K-doped catalyst. In contrast, both in situ XRD measurement tests and ToF SIMS results show a pronounced difference between the RuO + K/CZ catalyst and the other two systems, which indicates that the interaction of the surfaces with the reagents might be the cause of the discrepancy. The CO-TPD results show that this system retains more CO, i.e., the product, at adsorption sites, which might reduce the adsorption of other reagents, i.e., oxygen ions, CO, and propane, hence lowering the overall activity of the system.
在此，我们展示了一篇论文，该论文试图通过纳入能够对催化剂表面进行主动探测的表征方法，弥合在模拟气流中进行的CO氧化催化测试与更实际的废气流之间的差距。结果表明，不仅是表面上给定类型物种的丰度会影响系统的活性，还有从其表面提取离子的难易程度（飞行时间二次离子质谱）以及载体对进料组成变化的响应（可变气氛动态原位X射线衍射(XRD)）。该研究采用向催化剂(RuO/CZ)中掺杂少量碱金属(K或Na)碳酸盐的方法，以轻微改变其表面，从而深入了解可能导致模拟气流活性与复杂气流活性之间差异的参数。最显著的差异在于，在仅含氦气中的CO和O的模拟气流中，两种碱离子在175°C左右的温度下都能提高系统的活性，而在模拟贫氧条件下柴油发动机废气流的复杂气流中，K掺杂的催化剂比RuO/CZ和RuO+Na/CZ略差，在丙烷燃烧中则差得多。总氢消耗值（程序升温还原）和O/O比（X射线光电子能谱）都表明RuO+K/CZ系统介于另外两者之间，因此没有理由解释K掺杂催化剂的异常行为。相比之下，原位XRD测量测试和ToF SIMS结果都表明RuO+K/CZ催化剂与其他两个系统之间存在明显差异，这表明表面与试剂之间的相互作用可能是差异的原因。CO-TPD结果表明，该系统在吸附位点保留了更多的CO，即产物，这可能会减少其他试剂，即氧离子、CO和丙烷的吸附，从而降低系统的整体活性。
