TiO 2 /Ni Inverse-Catalysts Prepared by Atomic Layer Deposition (ALD)
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TiO2/Ni Inverse-Catalysts Prepared by Atomic Layer Deposition (ALD) Dong Wun Kim • Kwang-Dae Kim • Hyun Ook Seo • Nilay Kumar Dey • Myoung Joo Kim • Young Dok Kim Dong Chan Lim • Kyu Hwan Lee
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Received: 21 October 2010 / Accepted: 18 January 2011 / Published online: 22 April 2011 Ó Springer Science+Business Media, LLC 2011
Abstract Atomic layer deposition (ALD) was used to deposit TiO2 on Ni particles, and the catalytic activity of Ni for CO2 reforming of methane (CRM) was evaluated. In the presence of TiO2 islands on Ni surfaces, the onset temperature of the CRM reaction was lower than that of bare Ni. During the CRM reaction, carbon was deposited on the surface of bare Ni, which reduced the catalytic activity of the surface with time, and TiO2 islands were able to remove carbon deposits from the surface. When the Ni surface was completely covered with TiO2, the catalytic activity disappeared, demonstrating that tuning of the TiO2 coverage on Ni is important to maximize the activity of the CRM reaction. Keywords
Metal Ni Metal-oxide TiO2 CO2
1 Introduction Heterogeneous catalysts consist mostly of catalytically active metal nanoparticles supported by high surface area oxides [1, 2]. However, metal oxide catalysts supported by metal, often referred to as ‘‘inverse-catalysts’’ have also Electronic supplementary material The online version of this article (doi:10.1007/s10562-011-0601-7) contains supplementary material, which is available to authorized users. D. W. Kim K.-D. Kim H. O. Seo N. K. Dey M. J. Kim Y. D. Kim (&) Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Korea e-mail: [email protected] D. C. Lim K. H. Lee Materials Processing Division, Korea Institute of Materials Science, Changwon 641-010, Korea
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been studied [3–10]. Inverse-catalysts can help elucidate the structure of the active sites of heterogeneous catalysts. When different oxide supports are used for metal nanoparticles, different catalytic activities are often obtained. By changing the supporting materials, different structures (shape and size) of supported metal particles can form, resulting in various catalytic activities. On the other hand, various oxide supports can provide dissimilar metal/oxide interface sites, resulting in changes in catalytic activity. By using inverse-catalysts, one can study how the metal/oxide interface contributes to catalytic activity while imposing only a minor influence on the structure of the metal [3–6]. It has also been demonstrated that inverse-catalysts are sometimes catalytically more active than conventional catalysts composed of the same compounds [4]. In this study, we used atomic layer deposition (ALD) to prepare oxide thin films on Ni particles. Using ALD, the thickness of the thin films can be precisely controlled, making ALD suitable for synthesizing inverse-catalysts with various amounts of oxide coverage [11–14]. Therefore, oxide coverage can be tuned to produce structures with the highest possible catalytic activity. In order to study the effect of TiO2
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