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首页> 外文期刊>ACS catalysis >Identifying Dynamic Structural Changes of Active Sites in Pt-Ni Bimetallic Catalysts Using Multimodal Approaches
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Identifying Dynamic Structural Changes of Active Sites in Pt-Ni Bimetallic Catalysts Using Multimodal Approaches

机译：使用多式联运方法识别PT-NI双金属催化剂中活性位点的动态结构变化

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摘要

Alloy nanoparticle catalysts are known to afford unique activities that can differ markedly from their parent metals, but there remains a generally limited understanding of the nature of their atomic (and likely dynamic) structures as exist in heterogeneously supported forms under reaction conditions. Notably unclear is the nature of their active sites and the details of the varying oxidation states and atomic arrangements of the catalytic components during chemical reactions. In this work, we describe multimodal methods that provide a quantitative characterization of the complex heterogeneity present in the chemical and electronic speciations of Pt-Ni bimetallic catalysts supported on mesoporous silica during the reverse water gas shift reaction. The analytical protocols involved a correlated use of in situ X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), complimented by ex-situ aberration corrected Scanning Transmission Electron Microscopy (STEM). The data reveal that complex reactions occur between the metals and support in this system under operando conditions. These reactions, and the specific impacts of strong metal-silica bonding interactions, prevent the formation of alloy phases containing Ni-Ni bonds. This feature of structure provides high activity and selectivity for the reduction of CO2 to carbon monoxide without significant competitive levels of methanation. We show how these chemistries evolve to the active state of the catalyst: bimetallic nanoparticles possessing an intermetallic structure (the active phase) that are conjoined with Ni-rich, metal-silicate species.
机译：已知合金纳米颗粒催化剂负担来自母体金属的独特活动，该活性可以与母体金属显着不同，但仍然有限地了解在反应条件下以异均相支持的形式存在于异均相负载形式的原子（和可能的动态）结构的性质。值得注意的是，其活性位点的性质以及在化学反应期间催化组分的变化氧化状态和原子布置的细节。在这项工作中，我们描述了在逆转水气体换水反应期间提供了在介孔二氧化硅上负载的PT-Ni双金属催化剂的化学和电子防护中存在的复杂异质性的定量表征的多模式。分析方案涉及以原位像差校正扫描透射扫描透视电子显微镜（Stew）的与原位X射线吸收光谱（XAS）和漫反射红外傅里叶变换光谱（漂移）的相关性。数据显示，在操作扬说条件下，在该系统中的金属和支持之间发生复杂反应。这些反应和强金属二氧化硅键合相互作用的具体影响，防止形成含有Ni-Ni键的合金相。该结构的这种特征提供了高活性和选择性，可以减少二氧化碳，而无需显着竞争水平的甲烷化。我们展示了这些化学物质如何发展到催化剂的活性状态：具有与富含Ni的金属硅酸盐物质连体的金属间结构（活性相）的双金属纳米颗粒。

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