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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Three-Dimensional Nanoparticle Distribution and Local Curvature of Heterogeneous Catalysts Revealed by Electron Tomography
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Three-Dimensional Nanoparticle Distribution and Local Curvature of Heterogeneous Catalysts Revealed by Electron Tomography

机译：电子层析成像显示三维异质催化剂的三维纳米分布和局部曲率

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摘要

The size and shape of pores is a key factor in the successful deployment of mesoporous silicas as supports for high-activity catalytic nanoparticles. Critical concerns are the accessibility of catalyst particles to reactant species, the effect of the particle-support interaction on catalytic activity, and the stability of the system with respect to degradation or sintering. In the present work, high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) tomography has provided quantitative three-dimensional information about the location of bimetallic nanoparticles supported on and within disordered mesoporous silica (Grace Davison 634-type). The surface of the pore network was found to be fractal in nature (fractal dimension Ds ~ 2.4) with implications for the selectivity of the catalyst-support system. By measuring the location of catalyst particles as a function of the local curvature of the support, particle adsorption sites were classified. The distribution of nanoparticles within the interior of the support showed preferential adsorption on anticlastic ("saddle-shaped") surfaces, whereas nanoparticles adsorbed on the exterior surfaces of the support structure also demonstrated a strong preference for concave ("cup-like") regions. These results highlight the critical importance of three-dimensional characterization for quantitative evaluation of porous media and catalytic supports.
机译：孔的大小和形状是中孔二氧化硅成功用作高活性催化纳米颗粒载体的关键因素。关键问题是催化剂颗粒与反应物的可及性，颗粒与载体之间的相互作用对催化活性的影响以及系统在降解或烧结方面的稳定性。在目前的工作中，高角度环形暗场扫描透射电子显微镜（HAADF-STEM）层析成像技术提供了有关无序介孔二氧化硅（Grace Davison 634型）上及其内部支撑的双金属纳米粒子位置的定量三维信息。发现孔网络的表面本质上是分形的（分形维数Ds〜2.4），这暗示了催化剂-载体系统的选择性。通过测量催化剂颗粒的位置与载体局部曲率的关系，可以对颗粒的吸附位置进行分类。纳米颗粒在载体内部的分布显示出优先吸附在抗弹（“鞍形”）表面上，而纳米颗粒吸附在载体结构的外表面上也显示出强烈偏好凹入（“杯状”）区域。这些结果突出了三维表征对于多孔介质和催化载体的定量评估的至关重要性。

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