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Chem. Mater. 2006, 18, 5826-5828
Size-Induced Structural Modifications Affecting Co3O4 Nanoparticles Patterned in SBA-15 Silicas Ire`ne Lopes,† Nissrine El Hassan,† Hadjira Guerba,‡ Gilles Wallez,§ and Anne Davidson*,† UniVersite´ Pierre et Marie Curie, Laboratoire de Re´ actiVite´ de Surface, CNRS UMR 7609, 5 place Jussieu, 75252 Paris ce´ dex 05, France, UniVersite´ Pierre et Marie Curie, Laboratoire de Chimie de la Matie` re Condense´ e, CNRS UMR 7574, 5 place Jussieu, 75252 Paris ce´ dex 05, and De´ partement de Chimie, Faculte´ des Sciences, UniVersite´ Ferhat-Abbas, Se´ tif, Alge´ rie ReceiVed July 13, 2006 ReVised Manuscript ReceiVed October 27, 2006
Co3O4 is a very versatile oxide that is involved in many advanced physical applications (magnetic properties) and in heterogeneous catalysis: NOx reduction,1 CO oxidation (with2 or without3 gold promoter), and vapor-phase oxidation of organic molecules.4 Metallic Co0 particles formed by reduction of Co3O4 nanoparticles supported on periodic silicas have also been used for Fischer-Tropsch synthesis, which is the conversion of natural gas into long-chain paraffins.5-7 Many efforts have been made to obtain Co3O4 particles of controlled dimensions by “nanocasting”, i.e., by crystallization inside the pores of both aperiodic and periodic silicas (commercial, monoliths, MCM, SBA).3-11 Basic issues about the “nanocasting” strategy have been recently reviewed.12 Very little information is available on the structure of the patterned Co3O4 particles and their potential sizeinduced modifications in contrast with several other oxide nanoparticles (maghemite,13,14 ceria15). This lack of information mainly results from three experimental difficulties: (i) * To whom correspondence shoud be addressed. Tel: 33 (0)1 44 27 60 04. Fax: 33 (0)1 44 27 60 33. E-mail:
[email protected]. †LRS, Universite ´ Pierre et Marie Curie. ‡ LCMC, Universite ´ Pierre et Marie Curie. § Universite ´ Ferhat-Abbas.
(1) Wichterlova, B. Top. Catal. 2004, 28, 131. (2) Xu, X.; Li, J.; Hao, Z.; Zhao, W.; Hu, C. Mater. Res. Bull. 2006, 41, 406. (3) Wang, C.B.; Tang, C.W.; Gau, S. J.; Chien, S. H. Catal. Lett. 2005, 1-2, 59. (4) Vetrivel, S.; Pandurangan, A. J. Mol. Catal. A: Chem. 2005, 22, 269. (5) Martinez, A.; Lopez, C.; Marquez, F.; Dias, J. J. Catal. 2003, 220, 486. (6) Ohtsuka, Y.; Takahashi, Y.; Noguchi, M.; Arai, T.; Tarasaki, S.; Tsubouchi, N.; Wang, Y. Catal. Today 2004, 89, 419. (7) Khodakov, A. Y.; Griboval-Constant, A.; Bechara, R.; Zholobenko, V. L. J. Catal. 2002, 230, 2006. (8) Tian, B.Z.; Liu, X.; Solovyov, L.; Liu, Z.; Zang, H.; Zhang, Z.; Xie, S.; Zhang, F.; Tu, B.; Yu, C.; Terasaki, O.; Zhao, D. J. Am. Chem. Soc. 2003, 126, 865. (9) Wang, Y.; Yang, C.; Schmidt, W.; Spiethoff, B.; Bill, E.; Schuth, F. AdV. Mater. 2005, 17, 53. (10) Crowley, T. A.; Ziegler, K. J.; Lyons, D. M.; Erst, D.; Olin, M.; Morin, M. A.; Holmes, J. D. Chem. Mater. 2003, 15, 3518. (11) Smatt, J. H.; Spliethoff, B.; Rosenholm, J. B.; Linden, M. Chem. Commun. 2004, 2188. (12) Liu, A. H.; Schu¨th, F. AdV. Mater. 2006, 78, 1793. (13) Ayyub, P.; Multani, M.; Barma, M. J. Phys. Chem. C: Solid State Phys. 1988, 21, 2229. (14) Belin, T.; Guigue-Millot, N.; Caillot, T.; Aymes, D.; Niepce, J. C. J. Solid State Chem. 2002, 163, 459. (15) Zhang, F.; Chen, S. W.; Spanier, J. E.; Jin, Q.; Robinson, R. D.; Herman, I. P. Appl. Phys. Lett. 2002, 80, 127.
a small amount of calibrated particles is generally obtained, preventing investigations of size-related structural properties, (ii) pore size distributions in aperiodic silicas can be as wide as 20%, leading to poorly calibrated nanoparticles, (iii) the crystallization of oxide particles both inside and outside silica grains is difficult to avoid. The present work is devoted to the structural modifications affecting Co3O4 particles of controlled dimensions obtained by nanocasting in SBA silicas. To avoid interpretation difficulties, we have used SBA silicas of well-calibrated pore diameters (5.1, 5.6, and 7.3 nm) with a very narrow pore size distribution (
