Wei Xuejiao, Shao Bin, Zhou Yan, Li Yong, Jin Chuanchuan, Liu Jingyue, Shen Wenjie
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China.
Department of Physics, Arizona State University, Tempe, Arizona, 85287, USA.
Angew Chem Int Ed Engl. 2018 Aug 27;57(35):11289-11293. doi: 10.1002/anie.201805975. Epub 2018 Jul 24.
The geometrical structure of the Au-Fe O interfacial perimeter, which is generally considered as the active sites for low-temperature oxidation of CO, was examined. It was found that the activity of the Au/Fe O catalysts not only depends on the number of the gold atoms at the interfacial perimeter but also strongly depends on the geometrical structure of these gold atoms, which is determined by the size of the gold particle. Aberration-corrected scanning transmission electron microscopy images unambiguously suggested that the gold particles, transformed from a two-dimensional flat shape to a well-faceted truncated octahedron when the size slightly enlarged from 2.2 to 3.5 nm. Such a size-induced shape evolution altered the chemical bonding environments of the gold atoms at the interfacial perimeters and consequently their catalytic activity. For Au particles with a mean size of 2.2 nm, the interfacial perimeter gold atoms possessed a higher degree of unsaturated coordination environment while for Au particles with a mean size of 3.5 nm the perimeter gold atoms mainly followed the atomic arrangements of Au {111} and {100} facets. Kinetic study, with respect to the reaction rate and the turnover frequency on the interfacial perimeter gold atom, found that the low-coordinated perimeter gold atoms were intrinsically more active for CO oxidation. O isotopic titration and Infrared spectroscopy experiments verified that CO oxidation at room temperature occurred at the Au-Fe O interfacial perimeter, involving the participation of the lattice oxygen of Fe O for activating O and the gold atoms for CO adsorption and activation.
研究了通常被认为是CO低温氧化活性位点的Au-FeO界面周边的几何结构。发现Au/FeO催化剂的活性不仅取决于界面周边金原子的数量，还强烈取决于这些金原子的几何结构，而这又由金颗粒的尺寸决定。像差校正扫描透射电子显微镜图像明确表明，当尺寸从2.2nm略微增大到3.5nm时，金颗粒从二维平面形状转变为多面体截角八面体。这种尺寸诱导的形状演变改变了界面周边金原子的化学键合环境，从而改变了它们的催化活性。对于平均尺寸为2.2nm的金颗粒，界面周边的金原子具有更高程度的不饱和配位环境，而对于平均尺寸为3.5nm的金颗粒，周边金原子主要遵循Au{111}和{100}面的原子排列。关于界面周边金原子的反应速率和周转频率的动力学研究发现，低配位的周边金原子对CO氧化本质上更具活性。O同位素滴定和红外光谱实验证实，室温下的CO氧化发生在Au-FeO界面周边，涉及FeO晶格氧参与活化O以及金原子参与CO吸附和活化。
