Laan Petrus C M, Mekkering Martijn J, de Zwart Felix J, Troglia Alessandro, Bliem Roland, Zhao Kai, Geels Norbert J, de Bruin Bas, Rothenberg Gadi, Reek Joost N H, Yan Ning
Van't Hoff Institute for Molecular Sciences, University of Amsterdam Science Park 904 1098XH Amsterdam The Netherlands
Advanced Research Center for Nanolithography (ARCNL) Science Park 106 1098XG Amsterdam The Netherlands.
Catal Sci Technol. 2024 Aug 14;14(19):5662-5670. doi: 10.1039/d4cy00484a. eCollection 2024 Sep 30.
The local coordination environment of single atom catalysts (SACs) often determines their catalytic performance. To understand these metal-support interactions, we prepared Pt SACs on cerium dioxide (CeO) cubes, octahedra and rods, with well-structured exposed crystal facets. The CeO crystals were characterized by SEM, TEM, pXRD, and N sorption, confirming the shape-selective synthesis, identical bulk structure, and variations in specific surface area, respectively. EPR, XPS, TEM and XANES measurements showed differences in the oxygen vacancy density following the trend rods > octahedra > cubes. AC-HAADF-STEM, XPS and CO-DRIFTS measurements confirmed the presence of only single Pt sites, with different surface platinum surface concentrations. We then compared the performance of the three catalysts in ammonia borane hydrolysis. Precise monitoring of reaction kinetics between 30-80 °C gave Arrhenius plots with hundreds of data points. All plots showed a clear inflection point, the temperature of which (rods > octahedra > cubes) correlates to the energy barrier of ammonia borane diffusion to the Pt sites. These activity differences reflect variations in the - facet dependent - degree of stabilization of intermediates by surface oxygen lone pairs and surface-metal binding strength. Our results show how choosing the right macroscopic support shape can give control over single atom catalysed reactions on the microscopic scale.
单原子催化剂（SACs）的局部配位环境通常决定其催化性能。为了理解这些金属-载体相互作用，我们在具有结构良好的暴露晶面的二氧化铈（CeO）立方体、八面体和棒体上制备了铂单原子催化剂。通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）、粉末X射线衍射（pXRD）和氮吸附对CeO晶体进行了表征，分别证实了形状选择性合成、相同的体相结构以及比表面积的变化。电子顺磁共振（EPR）、X射线光电子能谱（XPS）、透射电子显微镜（TEM）和X射线吸收近边结构（XANES）测量表明，氧空位密度存在差异，遵循棒体>八面体>立方体的趋势。高角度环形暗场扫描透射电子显微镜（AC-HAADF-STEM）、XPS和一氧化碳漫反射红外傅里叶变换光谱（CO-DRIFTS）测量证实仅存在单铂位点，且表面铂表面浓度不同。然后我们比较了这三种催化剂在氨硼烷水解反应中的性能。在30-80°C之间对反应动力学进行精确监测，得到了具有数百个数据点的阿伦尼乌斯图。所有图都显示出一个明显的拐点，其温度（棒体>八面体>立方体）与氨硼烷扩散到铂位点的能垒相关。这些活性差异反映了表面氧孤对和表面-金属结合强度对中间体稳定程度的面依赖性变化。我们的结果表明，选择合适的宏观载体形状如何能够在微观尺度上控制单原子催化反应。
