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Measurements of d-band Center Shifts of Titanium Dioxide Catalyst Using Gold Nanoparticles in Carbon Monoxide Oxidation Reaction

Ahmed K. Jwad, Hussain A. Fadil, Sami R. Hmeed, Abbas K. Hashem

Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية
ISSN: 18132065 23091673 Year: 2018 Volume: 14 Issue: 3 Pages: 3-11
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

Abstract

It was reported previously that O adatoms adsorbed dissociatively on the 5-fold Ti rows of rutile TiO2 made the surface O-rich and reacted with CO molecules to form CO2. An electronic charge transfer taking place from gold nano-clusters to the O-rich TiO2 support played a crucial role to enhance the catalytic activity. In this study, we have further accumulated experimental data for the CO oxidation reaction enhanced by gold nano-clusters on the TiO2 surface. Based on the results obtained here and previously, we propose an “interface dipole model”, which explains the strong activity of Au nano-clusters supported on O-rich TiO2 in CO oxidation reaction. Simultaneously, we also discuss the cationic cluster model and the d-band model. The latter is, in particular, widely accepted to explain the activities of heterogeneous catalysts. Contrary to the d-band model, our ab initio calculations demonstrate that the d-band center for Au nano-clusters moves apart from the Fermi level with decreasing the cluster size and this is due to contraction of the Au-Au bond length.

Keywords

TiO2 catalyst --- carbon monoxide --- Oxidation reaction --- Nanoclusters