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Swelling and Delamination Behaviors of Birnessite-Type Manganese Oxide by Intercalation of Tetraalkylammonium Ions Zong-huai Liu,† Kenta Ooi,*,‡ Hirofumi Kanoh,‡ Wei-ping Tang,§ and Tahei Tomida†,| University of Tokushima, 2-1 Minamijosanjima, Tokushima, 770-0814 Japan, Shikoku National Industrial Research Institute, 2217-14, Hayashi-cho, Takamatsu, 761-0395 Japan, and Research Institute for Solvothermal Technology, 2217-43, Hayashi-cho, Takamatsu, 761-0301 Japan Received October 18, 1999. In Final Form: January 26, 2000 Intercalations of tetramethylammonium (TMA), tetraethylammonium (TEA), tetrapropylammonium (TPA), and tetrabutylammonium (TBA) ions into layered birnessite-type manganese oxide, BirMO(H), were studied in aqueous tetraalkylammonium hydroxide solutions with different concentrations. Expansions of the interlayer were not observed clearly in the TEA, TPA, or TBA systems. Stable colloidal suspensions were obtained in the TMA system at TAl/Hs (molar ratio of tetraalkylammonium ions over exchangeable protons in BirMO(H)) larger than 1. XRD analyses for these colloidal sediments in the wet state showed a short-range swelling by the TMA+ intercalation, with an increase in the basal spacing (dbs) from 0.73 to 1.56 nm. The basal spacing decreased stepwise from 1.56 through 1.27 to 0.96 nm with a decrease of the relative humidity during drying. The chemical analysis results showed that the cation intercalation progressed by an ion exchange mechanism. The intrinsic selectivity coefficient for intercalation had a tendency to decrease with an increase in the ionic radius of guest cations, probably owing to the larger steric hindrance for larger ions. The intercalation of TBA+ ions could be achieved by a two-step reaction involving treatment with (TMA)OH followed by (TBA)OH. The basal spacing increased from 1.56 to 2.19 nm due to the TBA+ intercalation. No long-range swelling was clearly observed. However, delamination took place and the layered structure collapsed when TMA+-intercalated samples obtained at TAl/Hs ) 25 were washed with distilled water. Delamination was also observed in the washing of the TBA+-intercalated sample. Freeze-drying of the washed slurry gave a flakelike manganese oxide, which supports the finding of delamination in wet conditions. Upon air-drying, the reassembling of the manganese oxide sheet progressed and the amorphous phase reverted to the layered structure with basal spacing of 0.96 nm. The origins of short-range swelling and the delamination observed in the BirMO(H)-TMA+ system are discussed in terms of attractive and repulsive forces by electrostatic interaction, hydration of interlayer cations, and interlayer hydrogen bonding.
Introduction Intercalation reactions by layered compounds have drawn much attention from both the fundamental and practical viewpoints.1-3 Intercalation of guest molecules brings about an expansion or a shrinking of the interlayer depending on the host structure as well as the nature of guest species. Expansion of the interlayer involving the intercalation of a solvent is called swelling. Two kinds of swelling behavior involving water molecules are observed for layered inorganic materials: a short-range (crystalline) swelling and a long-range (osmotic) swelling.4,5 The shortrange swelling is characterized by the formation of hydrate layers in the interlayer. This kind of swelling has been observed for a number of layered materials as well as clay minerals.4,6-13 The interlayer distance expands stepwise * To whom correspondence should be addressed. Tel.: +81-87869-3511. Fax: +81-87-869-3550. E-mail:
[email protected]. † University of Tokushima. ‡ Shikoku National Industrial Research Institute. § Research Institute for Solvothermal Technology. | E-mail:
[email protected]. (1) Scho¨llhorn, R. Chem. Mater. 1996, 8, 1747. (2) Barrer R. M. Zeolites and Clay Minerals as Sorbents and Molecular Sieves; Academic Press: London, 1978; p 407. (3) Clearfield, A., Ed. Inorganic Ion Exchange Materials; CRC Press: Boca Raton, FL, 1982. (4) Norrish, K. Discuss. Faraday Soc. 1954, 18, 120. (5) Zhang, F.; Low, P. F.; Roth, C. B. J. Colloid Interface Sci. 1995, 173, 34.
depending on the number of molecular layers of water. Recent MD and MC calculations for short-range swelling have succeeded in simulating the stepwise formation of a stable hydrate layer.14,15 Long-range swelling is associated with the formation of diffuse double layers and the consequent change of the electrostatic attractive force to an osmotic repulsive one.4 Theoretical and experimental studies on long-range swelling have been carried out extensively during the past decade on the basis of electrical double layer theory.14-20 (6) Lerf A.; Scho¨llhorn, R. Inorg. Chem. 1977, 16, 2950. (7) Sasaki, T.; Komatsu, Y.; Fujiki, Y. Chem. Mater. 1992, 4, 894. (8) Raveau, B. Rev. Chim. Mineral. 1984, 21, 391. (9) Gillery F. H. Am. Mineral. 1959, 44, 806. (10) Levy R.; Shainberg, I. Clay Clay Miner. 1972, 20, 37. (11) Cases, J. M.; Belend, I.; Besson, G.; Francois, M.; Uriot, J. P.; Thomas, F.; Poirier, J. E. Langmuir 1992, 8, 2730. (12) (a) Kittaka, S.; Uchida, N.; Kihara, T.; Suetsugi, T.; Sasaki, T. Langmuir 1992, 8, 245. (b) Kittaka, S.; Ayatsuka, Y.; Ohtani, K.; Uchida, N. J. Chem. Soc., Faraday Trans. 1 1989, 85, 3825. (13) Mohan, K. K.; Fogler, H. S. Langmuir 1997, 13, 2863. (14) Karaborni, S.; Smit, B.; Heidug, W.; Urai, J.; van Oort, E. Science 1996, 271, 1102. (15) (a) Skipper, N. T.; Sposito, G.; Chang, F.-R. C. Clays Clays Miner. 1995, 43, 294. (b) Skipper, N. T.; Refson, K.; McConnell, J. D. C. Clay Miner. 1989, 24, 411. (16) Greathouse, J. A.; Feller, S. E.; McQuarrie, D. A. Langmuir 1994, 10, 2125. (17) (a) Smalley, M. V. Langmuir 1994, 10, 2884. (b) Smalley, M. V.; Thomas, R. K.; Braganza, L. F.; Matsuo, T. Clays Clays Miner. 1989, 37, 474. (18) Low, P. F. Langmuir 1987, 3, 18.
10.1021/la9913755 CCC: $19.00 © 2000 American Chemical Society Published on Web 03/17/2000
Birnessite-Type Manganese Oxide
In addition to swelling, the delamination (exfoliation) of layered oxides into their elementary host sheets is typically observed for some of the clay minerals such as montmorillonite and smectite.2,4 Delamination by intercalation can be artificially achieved by some soft-chemical procedures in several classes of layered oxides.6,20-25 The delaminated colloidal nanosheets have attracted much attention due to their unique optical properties associated with a quantum effect and their potential as precursors for thin film devices. From the fundamental standpoint, they are expected to have unique chemical and physical properties distinctive from those in the stacked state. We are interested in the swelling and delamination behaviors of layered manganese oxides, since these reactions are expected to give precursors for novel cathode materials for secondary lithium batteries or a new functional catalysis. Synthesis, structures, and physicochemical properties for layered manganese oxides (birnessite, buserite, etc.) have been widely studied, and their ion exchange properties have been also reported.26-34 However, the swelling properties of layered manganese oxide have received relatively less attention compared with other layered oxide materials. The intercalation of alkylammonium ions into the layered manganese oxide causes the expansion of the interlayer.35-38 The expanded solid has been used as precursors to pillar with large Keggin ions [Al13O4(OH)24(H2O)12]7+ or to intercalate organic monomers followed by polymerization.35,36 The expansion of the interlayer has been used to distinguish layered manganese oxide from tunnel types in manganese nodule sediments.37 The intercalation of (C12H25)NMe3+ or TBA+ ions into sodium birnessite gives layered manganese oxides with a basal spacing of 2.41 or 1.28 nm, respectively;38 thus, they are expected to function as precursors for preparing mesoporous manganese oxides. (19) Viani, B. E.; Low, P. F.; Roth, C. B. J. Colloid Interface Sci. 1983, 96, 229. (20) (a) Sasaki, T.; Watanabe, M. J. Am. Chem. Soc. 1998, 120, 4682. (b) Sasaki, T.; Watanabe, M.; Hashizume, H.; Yamada, H.; Nakazawa, H. J. Am. Chem. Soc. 1996, 118, 8329. (21) Nadeau, P. H.; Wilson, M. J.; McHardy, W. J.; Tait, J. M. Science 1984, 225, 923. (22) Alberti, G.; Casciola, M.; Costantino, U. J. Colloid Interface Sci. 1985, 107, 256. (23) Treacy, M. M.; Rice, S. B.; Jacobsen, A. J.; Lewandowski, J. T. Chem. Mater. 1990, 2, 279. (24) Nazar, L. F.; Liblong, S. W.; Yin, X. T. J. Am. Chem. Soc. 1991, 113, 5889. (25) Abe, R.; Hara, M.; Kondo, J. N.; Domen, K.; Shinohara, K.; Tanaka, A. J. Mater. Res. 1998, 13, 861. (26) Block, S. L.; Duan, N.; Tian, Z. R.; Gilardo, O.; Zhou, H.; Suib, S. L. Chem. Mater. 1998, 10, 2619. (27) (a) Feng, Q.; Kanoh, H.; Ooi, K. J. Mater. Chem. 1999, 9, 319. (b) Feng, Q.; Kanoh, H.; Miyai, Y.; Ooi, K. Chem. Mater. 1995, 7, 1226. (c) Kanoh, H.; Tang, W. P.; Makita, Y.; Ooi, K. Langmuir 1997, 13, 6845. (d) Feng, Q.; Sun, E.-H.; Yanagisawa, K.; Yamasaki, N. J. Ceram. Soc. Jpn. 1997, 105, 564. (28) Burns, R. G.; Burns, V. M. Manganese Dioxide Symposium; Tokyo, 1980; Schumm, B., Jr., Joseph, H. M., Kozawa, A., Eds.; I. C. MnO2 Sample Office: Cleveland, OH, 1980; Vol. 2, p 97. (29) Stouff, P.; Boulegue, J. Am. Mineral. 1988, 73, 1162. (30) Post, J. E.; Veblen, D. R. Am. Mineral. 1990, 75, 477. (31) (a) Golden, D. C.; Chen, C. C.; Dixon, J. B. Clays Clay Miner. 1986, 34, 511. (b) Golden, D. C.; Chen, C. C.; Dixon, J. B. Clays Clay Miner. 1987, 35, 271. (32) Shen, Y.-F.; Sib, S. L.; O’Young, C.-L. J. Am. Chem. Soc. 1994, 116, 11020. (33) Aronson, B. J.; Kinser, A. K.; Passerini, S.; Smyrl, W. H.; Stein, A. Chem. Mater. 1999, 11, 949. (34) (a) Drits, V. A.; Silvester, E.; Gorshkov, A. I.; Manceau, A. Am. Mineral. 1997, 82, 946. (b) Silvester, E.; Manceau, A.; Drits, V. A. Am. Mineral. 1997, 82, 962. (35) Wong, S.-T.; Cheng, S.-F. Inorg. Chem. 1992, 31, 1165. (36) Ammundsen, B.; Wortham, E.; James, D. J.; Roziere, J. Mol. Cryst. Liq. Cryst. 1998, 311, 327. (37) Paterson, E. Am. Mineral. 1981, 66, 424. (38) Luo, J.; Suib, S. L. Chem. Commun. 1997, 1031.
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Mesoporous manganese oxide with mixed-valent semiconducting properties has been prepared from Mn(OH)2 with cetyltrimethyl bromide surfactant as micellar temperate.39 Novel tetraalkylammonium manganese oxide colloids with a platelike form 4-12 nm in diameter have been prepared by the reduction of tetraalkylammonium permanganate; their fine structures have been characterized by EXAFS measurement.40 These colloids are prepared in a delaminated form and can undergo selfassembly to produce a layered structure and show a unique semiconducting system. There have been relatively small studies on the swelling and delamination properties of layered manganese oxides from the physicochemical standpoint. In the present work, we carried out systematic studies on the intercalation of large organic ions into layered birnessite-type manganese oxide using tetraalkylammonium ions with different lengths of methylene chain. We used highly crystalline manganese oxide, because it was desirable to have highly regulated layered materials and also to have large manganese oxide nanosheets for precursors of new functional devices. Short-range swelling was observed by the intercalation of TMA+ ions and also by the two-step intercalation of TMA+ followed by TBA+ ions. The delamination of the stacked manganese oxide sheets was observed after the water washing of the intercalated compounds. A schematic diagram for the reactions of shortrange swelling and delamination is presented. The origins of these phenomena are discussed in terms of the attractive and repulsive forces acting between the sheets. Experimental Section Materials. The starting material, BirMO(H), was synthesized by the acid exchange from highly crystalline sodium birnessite as previously described.27d A mixed solution of 0.6 M (1 M ) 1 mol dm-3) NaOH and 2 M H2O2 was quickly poured into a 0.3 M Mn(NO3)2 solution and stirred for 25 min. The precipitates were subjected to hydrothermal treatment at 423 K for 16 h in a 2 M NaOH solution. The sodium birnessite obtained was acid treated with a 0.1 M HCl solution for 2 days at 298 K, washed with water, and dried at 343 K. The Na and Mn contents were determined by atomic absorption spectrometry, and the mean oxidation number of manganese was determined by a standard oxalic acid method.41 Water content was determined by the weight loss in the DTA-TG curves. The pH titration curve toward Na+ ions was obtained in 0.1 M NaCl + NaOH solutions at 298 K. The ion-exchange capacity was evaluated from the titration curves. Intercalation-Deintercalation Reactions. Intercalation of tetraalkylammonium ions was studied batchwise. Weighed samples (0.1 g) of BirMO(H) were soaked in tetraalkylammonium hydroxide solutions (25 cm3) with different concentrations for 7 days at 298 K. The amount of tetraalkylammonium hydroxide added ranged from 0.5- to 25-fold that of the exchangeable capacity for BirMO(H) (0.5 e TAl/Hs e 25). After soaking, the solid was filtered on a membrane filter and the filtrates were subjected to XRD analyses in their wet state. The hydroxide ion concentrations in the supernatant solutions were determined by acid titration. The filtrates were air-dried at a relative humidity of 40% at 298 K. The effect of relative humidity on the swelling was studied by equilibrating the sample with an atmosphere at a different humidity. Each filtrate in the wet state was washed with 20 cm3 of water, and the washed solid was subjected to XRD analysis in the wet state. Conventional air-drying was carried out at a relative humidity of 40% at 298 K. Freeze-dried samples were obtained using a freeze dryer for samples treated at 84 K. (39) Tian, Z. R.; Tong, W.; Wang, J. Y.; Duan, N. G.; Krishnan, V. V.; Suib, S. L. Science 1997, 276, 926. (40) (a) Ressler, T.; Brock, S. L.; Wong, J.; Suib, S. L. J. Phys. Chem. 1999, 103, 6407. (b) Brock, S. L.; Sanabria, M.; Suib, S. L.; Urban, V.; Thiyagarajan, P.; Potter D. I. J. Phys. Chem. B 1999, 103, 7416.
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Figure 2. pH titration curve of BirMO(H) toward Na+.
Figure 1. SEM images of birnessite (Na-type) and BirMO(H). Deintercalation of TMA+ ions from the interlayer was performed by mixing the TMA+ intercalated samples with a 0.1 M HCl solution at 298 K for 3 days. Total nitrogen (TN) and carbon (TC) concentrations in the supernatant solution were determined by GC with a Sumigraph type GCT-12N analyzer. The extractability of TMA+ ions was evaluated from the TN concentration in the supernatant solution. Intercalation-deintercalation of Na+ ions was also studied by the same procedure using a NaOH solution. Chemical Analyses. The Mn contents of the solids were determined by atomic absorption spectrometry after they were dissolved in a mixed solution of HCl and H2O2. The TC and TN contents of the intercalated solids were determined by a Sumigraph type NCH-21 NCH analyzer. Physical Properties. The solid from each step was subjected to XRD analysis using a Rigaku type RINT 1200 X-ray diffractometer with a graphite monochromator at 303 K. The diffractometer is equipped in a humidity/temperature controllable chamber. SEM observations were carried out with a Hitachi type S-2460N scanning electron microscope.
Results Characterization of BirMO(H). SEM images of synthetic birnessite (Na type) and BirMO(H) are given in Figure 1. Both samples have platelike forms with a thickness less than 0.1 µm. XRD analyses showed diffraction patterns corresponding to a layered structure with basal spacings of 0.72 and 0.73 nm for birnessite and BirMO(H), respectively. The pH titration curve of BirMO(H) toward Na+ ions is given in Figure 2. The pH value increases stepwise with the increase in the amount of OH- added, indicating that BirMO(H) has a multi-baseacid property. The cation exchange capacity is evaluated as 2.72 mmol/g. On the bases of chemical analysis results (Mn, Na, and water content), mean oxidation number (3.70) of manganese, and the cation exchange capacity, the chemical formula of BirMO(H) can be written as H3.33Na0.24Mn12O24‚9.6H2O. Short-Range Swelling by TMA+ Intercalation. Colloidal suspensions were obtained by treating BirMO(H) with TMA hydroxide solutions at TAl/Hs g 1. The suspensions were filtered, and the colloidal sediments were subjected to XRD measurement in their wet state (Figure 3). The expansion of the interlayer is not observed for the
Figure 3. Wet-state XRD patterns of manganese oxides treated with (TMA)OH solutions with different concentrations: (a) BirMO(H); (b) TAl/Hs ) 0.5; (c) TAl/Hs ) 1; (d) TAl/Hs ) 5; (e) TAl/Hs ) 10; (f) TAl/Hs ) 25.
sample at TAl/Hs ) 0.5; the pattern resembles that of the parent BirMO(H). For the sample at TAl/Hs ) 1, new peaks corresponding to a dbs of 1.56 nm appear in addition to the original peaks corresponding to dbs ) 0.73 nm. For samples at TAl/Hs g 5, the peaks corresponding to dbs ) 1.56 nm alone are observed and they strengthen with increasing TAl/Hs. Sharp diffraction lines up to the fifth order indicate a highly ordered hydrate structure, similar to the case of TBA+ intercalation into the protonic titanate.20a The detailed structural analysis, which will be shown below, suggests the formation of molecular layers of water in the interlayer, accompanied by the intercalation of TMA+ ions. This indicates that the intercalation of TMA+ ions from (TMA)OH solutions brings about a short-range swelling along the layers but not a long-range swelling. The rate of swelling was studied by changing the soaking time at TAl/Hs ) 25. The uniform phase corresponding to dbs )
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Table 1. Amounts of Cation Intercalated and OHConsumeda
Kc ) XMaH/XHaM ) (XM[H]/XH[M])(γH/γM)
(2)
cation Mn OHintercalated content intercalated consumed cation M+l/Hs (mmol/g) (mmol/g) M+s/Mn (mmol/g)
= (XMKw/XH[M][OH])
(2′)
Na+ TMA+
washing TEA+ TPA+ TBA+
25 0.5 1 5 10 25 25 1 1 1
2.42 0.60 1.27 1.47 1.96 2.34 1.67 0.24 0.18 0.11
8.67 9.11 9.25 8.97 8.92 8.85 8.87 9.28 9.30 9.28
0.279 0.066 0.137 0.164 0.220 0.264 0.188 0.026 0.019 0.012
1.32 1.50
0.26
