Electrochemical Properties of Blockcopolymer Templated Mesoporous Silicates with Heteropolyacids clusters
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Electrochemical Properties of Blockcopolymer Templated Mesoporous Silicates with Heteropolyacids clusters Hui Suk Yun,a Makoto Kuwabara,a Hao Shen Zhou,b and Itaru Honma*b Dept. of Materials Science, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan b National Institute of Advanced Industrial Science and technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, Japan, *E-mail: [email protected] a
ABSTRACT In this paper, we have studied a method of loading 12-tungstophosphoric acid (H3PW12O40; PWA) into blockcopolymer templated (designated EO20PO70EO20; Pluronic P-123) mesoporous SiO2 framework without a disordering of mesostructure and without remarkable decrease of specific surface area through one-step condensation process. A precursor solution is initially prepared by TEOS (tetraethoxysilane) hydrolyzed with templating polymer (eg. triblock copolymer), and then mixed directly with PWA to condense mesoporous silicate products that incorporate PWA clusters in the framework. Heteropolyanions are possibly incorporated in the framework silicates. Electrochemical properties of these PWA impregnated mesoporous silicates were studied as electrode materials of Li ion battery as well as solid proton conductors. INTRODUCTION Nanostructured mesoporous materials have attracted much attention recently due to their potential applications for catalysts, sensors, size- and shape-selective separation media. The nanostructure can be controlled by a variety of self assembling amphiphiles as template molecules through hydrolysis and polycondensation reaction at the interfaces. Novel structural properties of high surface area and lamellar, hexagonal or cubic arrays of uniform pore sizes within 2-50nm are suitable for advanced catalysts as well as sensors. Since the discovery of M41S families (MCM-41, MCM-48, MCM-50)[1], researches for providing better functional property on the mesoporous materials have been studied. Transition metals (Ti, Ta, V, Sn, Mn, W, Mo) or heteropoly acids (HPAs) were incorporated into mesoporous silica or mesoporous transition metal oxide materials[2-3, 5-10]. In the mean time, Keggin-type HPAs have stimulated considerable research in both heterogeneous and homogeneous catalysis, solid electrolytes, and aqueous solutions in fuel cells due to their excellent thermal, redox stability and special electrocatalytic properties. 12-tungstophosphoric acid (H3PW12O40; PWA) - the strongest acid in the HPAs series- is particularly recommended [3-10]. PWA are normally dispersed on suitable supports such as high surface area SiO2 since the bulk PWA have very low specific surface area (
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