Kang Jindong, Mahapatra Mausumi, Rui Ning, Orozco Ivan, Shi Rui, Senanayake Sanjaya D, Rodriguez José A
Department of Chemistry, SUNY at Stony Brook, Stony Brook, New York 11794, USA.
Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
J Chem Phys. 2020 Feb 7;152(5):054702. doi: 10.1063/1.5139237.
Indium oxide has received attention as an exciting candidate for catalyzing the CO hydrogenation to methanol due to its high selectivity (>80%). Compared to the extent of research on the activity of indium oxide-based powder catalysts, very little is known about the phenomena associated with the formation of surface alloys involving indium or the growth mechanism for indium oxide nanoparticles. In this report, scanning tunneling microscopy and X-ray photoelectron spectroscopy (XPS) were employed to elucidate the growth mode, structure, and chemical state of In/Au(111) alloys and InO/Au(111) inverse model catalysts. Our study reveals distinct morphological differences between In/Au(111) and InO/Au(111), and the InO structure also depends strongly on the preparation conditions. In/Au surface alloy systems with extremely low coverage (0.02 ML) form islands preferentially on the elbow sites of reconstructed Au(111) herringbone, regardless of hexagonally closed packed and face centered cubic stacking. At higher coverage (0.1 ML), the In islands expand over the herringbone in the ⟨110⟩ direction and create two dimensional domain structures over the entire surfaces. Moreover, this 2D domain structure is disturbed by temperature with high dispersion of indium atoms observed during the annealing process. Oxidation of the In/Au(111) surface alloys with O at 550 K produces InO/Au(111) systems which contain various sizes of InO aggregates (from 0.7 nm to 10 nm). On the other hand, InO/Au(111) surfaces prepared by vapor deposition of In at 550 K in an O background exhibit highly dispersed and uniformly small InO particles (∼1 nm). Both InO systems were confirmed to be partially oxidized by XPS.
氧化铟因其高选择性（>80%）而成为催化CO加氢制甲醇的一个令人兴奋的候选材料，受到了关注。与基于氧化铟的粉末催化剂活性的研究程度相比，关于涉及铟的表面合金形成相关现象或氧化铟纳米颗粒的生长机制知之甚少。在本报告中，采用扫描隧道显微镜和X射线光电子能谱（XPS）来阐明In/Au(111)合金和InO/Au(111)反相模型催化剂的生长模式、结构和化学状态。我们的研究揭示了In/Au(111)和InO/Au(111)之间明显的形态差异，并且InO结构也强烈依赖于制备条件。覆盖率极低（0.02 ML）的In/Au表面合金系统优先在重构的Au(111)人字形结构的肘部位置形成岛状物，而不管是六方密堆积和面心立方堆积。在较高覆盖率（0.1 ML）时，In岛在人字形结构上沿<110>方向扩展，并在整个表面上形成二维畴结构。此外，这种二维畴结构会受到温度的干扰，在退火过程中观察到铟原子的高度分散。在550 K下用O氧化In/Au(111)表面合金会产生包含各种尺寸InO聚集体（从0.7 nm到10 nm）的InO/Au(111)系统。另一方面，在550 K的O气氛中通过铟的气相沉积制备的InO/Au(111)表面呈现出高度分散且均匀的小InO颗粒（~1 nm）。通过XPS证实这两种InO系统均被部分氧化。
