Department of Physics and Science of Advanced Materials Program , Central Michigan University , Mt. Pleasant , Michigan 48859 , United States.
Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States.
ACS Appl Mater Interfaces. 2018 Apr 4;10(13):10870-10881. doi: 10.1021/acsami.7b19574. Epub 2018 Mar 23.
We present results from combined in situ infrared spectroscopy and total X-ray scattering studies on the evolution of catalytically active sites in exemplary binary and ternary Pt-based nanoalloys during a sequence of CO oxidation-reactivation-CO oxidation reactions. We find that when within a particular compositional range, the fresh nanoalloys may exhibit high catalytic activity for low-temperature CO oxidation. Using surface-specific atomic pair distribution functions (PDFs) extracted from the in situ total X-ray scattering data, we find that, regardless of their chemical composition and initial catalytic activity, the fresh nanoalloys suffer a significant surface structural disorder during CO oxidation. Upon reactivation in oxygen atmosphere, the surface of used nanoalloy catalysts both partially oxidizes and orders. Remarkably, it largely retains its structural state when the nanoalloys are reused as CO oxidation catalysts. The seemingly inverse structural changes of studied nanoalloy catalysts occurring under CO oxidation and reactivation conditions affect the active sites on their surface significantly. In particular, through different mechanisms, both appear to reduce the CO binding strength to the nanoalloy's surface and thus increase the catalytic stability of the nanoalloys. The findings provide clues for further optimization of nanoalloy catalysts for the oxidation of carbonaceous species through optimizing their composition, activation, and reactivation. Besides, the findings demonstrate the usefulness of combined in situ infrared spectroscopy and total X-ray scattering coupled to surface-specific atomic PDF analysis to the ongoing effort to produce advanced catalysts for environmentally and technologically important applications.
我们展示了在一系列 CO 氧化-再激活-CO 氧化反应中，对二元和三元 Pt 基纳米合金中催化活性位点演变进行原位红外光谱和全 X 射线散射联合研究的结果。我们发现，当处于特定的组成范围内时，新鲜的纳米合金可能表现出低温 CO 氧化的高催化活性。通过从原位全 X 射线散射数据中提取的表面特定原子配分函数（PDF），我们发现，无论其化学组成和初始催化活性如何，新鲜的纳米合金在 CO 氧化过程中都会遭受显著的表面结构无序。在氧气气氛中再激活时，用过的纳米合金催化剂的表面部分氧化并有序化。值得注意的是，当纳米合金再次用作 CO 氧化催化剂时，它在很大程度上保留了其结构状态。在 CO 氧化和再激活条件下，研究中的纳米合金催化剂发生的看似相反的结构变化，显著影响了其表面的活性位点。特别是，通过不同的机制，两者似乎都降低了 CO 与纳米合金表面的结合强度，从而提高了纳米合金的催化稳定性。这些发现为通过优化其组成、激活和再激活来进一步优化纳米合金催化剂，以用于氧化含碳物种提供了线索。此外，这些发现证明了原位红外光谱和全 X 射线散射与表面特定原子 PDF 分析相结合，对于开发用于环境和技术重要应用的先进催化剂的持续努力是有用的。
