贵金属纳米颗粒在 CO 氧化过程中的结构变化及其对催化剂活性的影响。
Structural changes in noble metal nanoparticles during CO oxidation and their impact on catalyst activity.
机构信息
Department of Physics, National University of Singapore, Singapore, 117551, Singapore.
Centre for BioImaging Sciences, Department of Biological Sciences, National University of Singapore, Singapore, 117557, Singapore.
出版信息
Nat Commun. 2020 May 1;11(1):2133. doi: 10.1038/s41467-020-16027-9.
The dynamical structure of a catalyst determines the availability of active sites on its surface. However, how nanoparticle (NP) catalysts re-structure under reaction conditions and how these changes associate with catalytic activity remains poorly understood. Using operando transmission electron microscopy, we show that Pd NPs exhibit reversible structural and activity changes during heating and cooling in mixed gas environments containing O and CO. Below 400 °C, the NPs form flat low index facets and are inactive towards CO oxidation. Above 400 °C, the NPs become rounder, and conversion of CO to CO increases significantly. This behavior reverses when the temperature is later reduced. Pt and Rh NPs under similar conditions do not exhibit such reversible transformations. We propose that adsorbed CO molecules suppress the activity of Pd NPs at lower temperatures by stabilizing low index facets and reducing the number of active sites. This hypothesis is supported by thermodynamic calculations.
催化剂的动态结构决定了其表面活性位点的可用性。然而，纳米颗粒（NP）催化剂在反应条件下如何重新结构，以及这些变化如何与催化活性相关联，仍然知之甚少。本文使用原位透射电子显微镜，表明 Pd NPs 在含有 O 和 CO 的混合气体环境中加热和冷却过程中表现出可逆的结构和活性变化。在 400°C 以下，NP 形成平坦的低指数晶面，对 CO 氧化无活性。在 400°C 以上，NP 变得更圆，CO 向 CO 的转化率显著增加。当温度随后降低时，这种行为会逆转。在类似条件下的 Pt 和 Rh NPs 则没有表现出这种可逆转变。我们提出，吸附的 CO 分子通过稳定低指数晶面和减少活性位点数来抑制低温下 Pd NPs 的活性。这一假设得到了热力学计算的支持。
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