Chen Yizhen, Sun Hanlei, Gates Bruce C
Department of Chemical Engineering, University of California-Davis, Davis, CA, 95616, USA.
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Small. 2021 Apr;17(16):e2004665. doi: 10.1002/smll.202004665. Epub 2020 Nov 13.
When metal nanoparticles on supports are made smaller and smaller-to the limit of atomic dispersion-they become cationic and take on new catalytic properties that are only recently being discovered. The synthesis of these materials is reviewed, including their structure characterization-especially by atomic-resolution electron microscopy and X-ray absorption and infrared spectroscopies-and relationships between structure and catalyst performance, for reactions including hydrogenations, oxidations, and the water gas shift. Structure determination is challenging because of the intrinsic nonuniformity of the support surfaces-and therefore the structures on them-but fundamental understanding has advanced rapidly, benefiting from nearly uniform catalysts consisting of metals on well-defined-crystalline-supports and their characterization by spectroscopy and microscopy. Recent advances in atomic-resolution electron microscopy have spurred the field, providing stunning images and deep insights into structure. The iridium catalysts have typically been made from organoiridium precursors, opening the way to understanding and control of the metal-support bonding and ligands on the metal, including catalytic reaction intermediates. Platinum catalysts are usually made with less precision, from salt precursors, but they catalyze a wider array of reactions than the iridium, typically being stable at higher temperatures and seemingly offering rich prospect for discovery of new catalysts.
当负载型金属纳米颗粒变得越来越小，直至达到原子分散极限时，它们会变成阳离子并呈现出一些直到最近才被发现的新催化特性。本文综述了这些材料的合成方法，包括其结构表征，特别是通过原子分辨率电子显微镜、X射线吸收光谱和红外光谱进行的表征，以及结构与催化剂性能之间的关系，涉及氢化、氧化和水煤气变换等反应。由于载体表面固有的不均匀性，因此其上的结构的确定具有挑战性，但得益于由明确结晶载体上的金属组成的近乎均匀的催化剂及其通过光谱学和显微镜进行的表征，基础认识已迅速取得进展。原子分辨率电子显微镜的最新进展推动了该领域的发展，提供了令人惊叹的图像并对结构有了深入了解。铱催化剂通常由有机铱前体制备而成，这为理解和控制金属-载体键合以及金属上的配体（包括催化反应中间体）开辟了道路。铂催化剂通常由盐前体以较低的精度制备，但它们催化的反应种类比铱催化剂更多，通常在较高温度下稳定，似乎为发现新催化剂提供了广阔前景。
