Dery Shahar, Mehlman Hillel, Hale Lillian, Carmiel-Kostan Mazal, Yemini Reut, Ben-Tzvi Tzipora, Noked Malachi, Toste F Dean, Gross Elad
Institute of Chemistry, The Hebrew University, Jerusalem 91904, Israel.
The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel.
ACS Catal. 2021 Aug 6;11(15):9875-9884. doi: 10.1021/acscatal.1c01987. Epub 2021 Jul 21.
Metal-support interactions have been widely utilized for optimizing the catalytic reactivity of oxide-supported Au nanoparticles. Optimized reactivity was mainly detected with small (1-5 nm) oxide-supported Au nanoparticles and correlated to highly reactive sites at the oxide-metal interface. However, catalytically active sites are not necessarily restricted to the interface but reside as well on the Au surface. Uncovering the interconnection between reactive sites located at the interface and those situated at the metal surface is of crucial importance for understanding the reaction mechanism on Au nanoparticles. Herein, high-spatial-resolution IR nanospectroscopy measurements were conducted to map the localized reactivity in hydrogenation reactions on oxide-supported Au particles while using nitro-functionalized ligands as probes molecules. Comparative analysis of the reactivity pattern on single particles supported on various oxides revealed that oxide-dependent reactivity enhancement was not limited to the oxide-metal interface but was detected throughout the Au particle, leading to site-independent reactivity. These results indicate that reactive Au sites on both the oxide-metal interface and metal surface can activate the nitro groups toward hydrogenation reactions. The observed influence of oxide support (TiO > SiO > AlO) on the overall reactivity pattern specified that hydrogen dissociation occurred at the oxide-metal interface, followed by highly efficient intraparticle hydrogen atom diffusion to the interior parts of the Au particle. In contrast to Au particles, the oxide-metal interface had only a minor impact on the reactivity of supported Pt particles in which hydrogen dissociation and nitro group reduction were effectively activated on Pt sites. Single-particle measurements provided insights into the relative reactivity pattern of oxide-supported Au particles, revealing that the less-reactive Au metal sites can activate hydrogenation reactions in the presence of hydrogen atoms that diffuse from the Au/oxide boundary.
金属-载体相互作用已被广泛用于优化氧化物负载金纳米颗粒的催化反应活性。优化后的反应活性主要在尺寸较小（1-5纳米）的氧化物负载金纳米颗粒中检测到，并且与氧化物-金属界面处的高活性位点相关。然而，催化活性位点不一定局限于界面，也存在于金表面。揭示位于界面处的活性位点与位于金属表面的活性位点之间的相互联系对于理解金纳米颗粒上的反应机理至关重要。在此，进行了高空间分辨率红外纳米光谱测量，以绘制氧化物负载金颗粒上氢化反应中的局部反应活性，同时使用硝基官能化配体作为探针分子。对负载在各种氧化物上的单个颗粒的反应活性模式进行的比较分析表明，氧化物依赖性反应活性增强并不局限于氧化物-金属界面，而是在整个金颗粒中都能检测到，从而导致与位点无关的反应活性。这些结果表明，氧化物-金属界面和金属表面上的活性金位点均可激活硝基的氢化反应。观察到的氧化物载体（TiO＞SiO＞AlO）对整体反应活性模式的影响表明，氢解离发生在氧化物-金属界面，随后颗粒内的氢原子高效扩散至金颗粒内部。与金颗粒不同，氧化物-金属界面对负载的铂颗粒的反应活性影响较小，在铂颗粒中，氢解离和硝基还原在铂位点上被有效激活。单颗粒测量为氧化物负载金颗粒的相对反应活性模式提供了见解，揭示了活性较低的金金属位点在存在从金/氧化物边界扩散而来的氢原子时能够激活氢化反应。
