Supported Pd and PdAu Nanoparticles on Ti-MCM-41 Prepared by a Photo-assisted Deposition Method as Efficient Catalysts f
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Supported Pd and PdAu Nanoparticles on Ti-MCM-41 Prepared by a Photo-assisted Deposition Method as Efficient Catalysts for Direct Synthesis of H2O2 from H2 and O2 Kohsuke Mori Æ Takashi Araki Æ Sayoko Shironita Æ Joji Sonoda Æ Hiromi Yamashita
Received: 9 March 2009 / Accepted: 22 May 2009 / Published online: 12 June 2009 Ó Springer Science+Business Media, LLC 2009
Abstract An efficient methodology to synthesize highly active Pd nanoparticles using a single-site photocatalyst under UV-light irradiation has been developed for the synthesis of hydrogen peroxide (H2O2) from H2 and O2. By the photo-assisted deposition (PAD) method, Pd precursor can be deposited directly on the photo-excited tetrahedrally coordinated metal-oxide moiety within the silica frameworks, and subsequently transformed into Pd nanoparticles by H2 reduction. The mean diameter of the deposited Pd particles determined by CO adsorption and the catalytic activities in the direct synthesis of H2O2 were strongly dependent on the preparation method and kind and/or amount of metal-oxide moieties. Here, the use of Ti-containing mesoporous silica (Ti/Si = 0.01) acted as a most efficient support for the above reaction. The PAD method also provides PdAu bimetallic nanoparticles from an aqueous solution of mixture of PdCl2 and HAuCl4. The PdAu/Ti-MCM-41 catalyst prepared by the PAD method was shown to perform significantly better activity than the pure Pd/Ti-MCM-41. Keywords Photo-assisted deposition Single-site photocatalyst Ti-containing mesoporous silica Metal nanoparticles
K. Mori T. Araki S. Shironita J. Sonoda H. Yamashita (&) Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan e-mail: [email protected]
1 Introduction The exploitation of new methodology for the synthesis of supported metal catalysts is significantly motivated by the fundamental industrial and academic interest [1, 2]. There are a number of criteria for practical supported metal catalysts including specific catalyst-support interaction, resistance to agglomerization, site isolation and good accessibility of substrate molecules, mechanical robustness, and low synthetic cost, etc. This multidimensional problem is complex, thus the design and synthetic control of promising catalysts is a serious technological challenge. The most convenient methods for attaining the immobilization of metal nanoparticles on high surface area support materials are the incipient wetness technique and the ion-exchange method, in which the support material is impregnated with metal precursors in the solution phase, followed by activation under a reducing atmosphere [3, 4]. This process can be further refined by post-synthesis modification of the support materials which promote the interaction between the metal precursor and surface [5]. Owing to its inherent simplicity, this is successful for the large scale production of catalysts, but, often results in non-uniform distribution of the active
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