• Helveg, Stig
• Lauritsen, Jeppe Vang
• Besenbacher, Flemming
• Simonsen, Søren Bredmose
• Meinander, Kristoffer
• Jensen, Thomas Nørregaard

Abstract

ATOMIC-SCALE NON-CONTACT ATOMIC FORCE STUDIES OF ALUMINA SUPPORTED NANOPARTICLES<br/>Thomas N. Jensen, Kristoffer Meinander, Flemming Besenbacher and Jeppe V. Lauritsen<br/>Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark<br/><br/>Heterogeneous catalysis plays a crucial role in the society today, both as the means for environmental protection and as the backbone technology for most of the chemical industries. Among important processes based on heterogeneous catalysis are biomass conversion, steam reforming of methane and the synthesis of synthetic fuel from hydrocarbons, coal, petroleum coke or biomass. The development of new catalysts is given a very high priority since they facilitate a much better utilization of our scarce energy reserves and it can drive the concept of waste-free ‘green’ chemistry and the development of a sustainable energy sector. Metal oxide surfaces like MgAl2O4 (spinel) and Al2O3 (alumina) play major roles in heterogeneous catalysis as catalyst supports, and these surfaces have previously been extensively studied, because of their outstanding mechanical stability at high temperatures. A better understanding of the surface structure of such support materials is a prerequisite for the synthesis of more sintering stable catalysts and the realizations of nanocatalysts implementing catalyst particles with a tailored size and morphology.<br/><br/>In the last two decades the atomic force microscope (AFM) has become one of the premier tools for studying surfaces at the nanometre scale [1]. When operated in the so-called non-contact mode (nc-AFM), this technique yields genuine atomic resolution and offers a unique tool for atomic-scale studies of clean surfaces, as well as, nanoparticles and thin films on these surfaces irrespective of the substrate being electrically conducting or non-conducting [2]. We use nc-AFM to study the growth, shape and size of nanoparticles on spinel and alumina surfaces. In addition to this, we have grown a transition alumina thin film on a spinel surface in order to characterize such a film as well as studying the catalytic properties of nanoparticles deposited on it (see figure 1).<br/><br/>Figure 1: Schematic drawing of nanoparticles deposited on an alumina film grown on a spinel surface and non-contact AFM image of the MgAl2O4 surface showing the initial growth of an alumina film from the step edges.<br/><br/>[1] Giessibl, F.J. Rev. Mod. Phys. 75, 949 (2003)<br/>[2] Lauritsen, J.V. and Reichling, M., J. Phys.: Condens. Matter 22, 263001 (2010)<br/><br/>E-mail: tnj@inano.au.dk<br/>www: http://inano.au.dk/organization/research-groups/nanocatalysis-lab-lauritsen/

Topics

• nanoparticle
• impedance spectroscopy
• surface
• thin film
• atomic force microscopy
• drawing
• sintering