J. Am. Chem. Soc. 1998, 120, 10837-10846
10837
Kinetic Study of the Intercalation of Cobaltocene by Layered Metal Dichalcogenides with Time-Resolved in Situ X-ray Powder Diffraction John S. O. Evans,† Stephen J. Price, Heng-Vee Wong, and Dermot O’Hare* Contribution from the Inorganic Chemistry Laboratory, UniVersity of Oxford, South Parks Road, Oxford, OX1 3QR, U.K. ReceiVed June 1, 1998
Abstract: Energy-dispersive X-ray diffraction (EDXRD) has been used to perform in situ kinetic studies on the intercalation of cobaltocene, Co(η-C5H5)2, into the layered dichalcogenides ZrS2, 2H-SnS2, 2H-SnSe2, 2H-TaS2, 2H-NbS2, 1T-TaS2, and TiS2. Integrated intensities of the Bragg reflections have been used to determine the extent of reaction (R) versus time for each of these reactions. The half-lives (t1/2) for reaction of an excess of cobaltocene with ZrS2, 2H-SnS2, 2H-SnSe2, 2H-TaS2, 2H-NbSe2, and TiS2 at 120 °C in dimethoxyethane were found to be 60000 s, respectively. A number of kinetic models have been considered, including the Avrami-Erofeyev (m ) 1.5) deceleratory nuclei-growth model and statistical simulation. The activation energy for the intercalation of Co(η-C5H5)2 in 2H-SnS2 has been determined to be 41 kJ mol-1. The concentration and solvent dependence of the rate of Co(η-C5H5)2 intercalation into 2H-SnS2 has also been determined. Surprisingly we find that the rate of intercalation is invariant to the initial Co(η-C5H5)2 concentration over the whole concentration range studied.
Introduction Some of the earliest and most extensive studies of the kinetics of intercalation reactions were carried out with graphite crystals. For example, Hooley and co-workers1,2 investigated the weight gain of a graphite flake in a bromine atmosphere. More recently, other groups have looked at the kinetics of domain interconversion in graphite intercalation compounds (GIC’s) from both an experimental3-8 and theoretical9-11 viewpoint. Surprisingly, much less attention has been focused on kinetic and mechanistic investigations of other intercalation systems such as transition metal chalcogenide intercalation or intercalation in clay minerals. This disparity may be attributable to the difficulty of performing structural studies on chalcogenide samples which, unlike graphite intercalation compounds, are not readily available as large oriented single crystals. Without the coherent scattering from planes of oriented crystal samples, the quality of diffraction spectra that can be obtained on time scales feasible for extracting kinetic data is usually too poor to be of any conceivable use. † Current address: Department of Chemistry, University Science Laboratories, South Road, Durham, DH1 3LE. (1) Hooley, J. G. Carbon 1973, 11, 225. (2) Hooley, J. G. Can. J. Chem. 1962, 40, 749. (3) Qian, X. W.; Stump, D. R.; S. A. Solin. Phys. ReV. B 1986, 33, 575669. (4) Mcghie, A. R.; Milliken, J.; Fischer, J. E. Mol. Cryst. Liq. Cryst. 1982, 86, 1969. (5) Milliken, J.; Fischer, J. E.; Mcghie, A. R. Carbon 1982, 20, 134. (6) Kim, H. J.; Fischer, J. E. Phys. ReV. B: Condens. Matter 1986, 33, 4349-4351. (7) Huang, Y. Y.; Stump, D. R.; Solin, S. A.; Heremans, J. Solid State Commun. 1987, 61, 469-473. (8) Hooley, J. G. Carbon 1985, 23, 579-584. (9) Ulloa, S. E.; Kirczenow, G. Phys. ReV. Lett. 1985, 55, 218-221. (10) Kirczenow, G. Synth. Met. 1988, 23, 1-6. (11) Kirczenow, G. Phys. ReV. Lett. 1985, 55, 2810-2813.
Consequently, researchers turned to indirect methods such as titration,12,13 mass gain,14,15 electrochemical methods,16-18 and spectroscopic methods19-23 to obtain kinetic data on the intercalation reactions of layered metal chalcogenides. Until recently only a limited number of time-resolved diffraction studies on metal chalcogenide intercalation had been reported.24-33 (12) Subba-Rao, G. V.; Shafer, M. W. J. Phys. Chem. 1975, 79, 557560. (13) Acrivos, J. V.; Dellos, C.; Topsoe, N. Y.; Salem, J. R. J. Phys. Chem. 1975, 79, 3003-10. (14) Kikkawa, S. J. Solid State Chem. 1980, 31, 249-255. (15) Dines, M. B. Science 1975, 188, 1210. (16) Bruce, P. G.; Saidi, M. Y. Solid State Ionics 1992, 51, 187-190. (17) Deroo, D.; Pedone, D.; Daland, F. J. Appl. Electrochem. 1990, 20, 835-840. (18) Riekel, C.; Reznik, H.; Schollhorn, R. J. Solid State Chem. 1980, 34, 253-262. (19) Butz, T.; Saitovitch, H.; Lerf, A. Chem. Phys. Lett. 1979, 65, 146149. (20) Butz, T.; Huebler, A. NuoVo Cimento Soc. Ital. Fis. 1983, 2D, 19711976. (21) Butz, T.; Lerf, A.; Besenthal, J. O. ReV. Chim. Miner. 1984, 21, 556-587. (22) Butz, T.; Lerf, A.; Besenhard, J. O. ReV. Chim. Miner. 1984, 21, 556-587. (23) Ganal, P.; Butz, T.; Lerf, A. Synth. Met. 1989, 34, 641-5. (24) Riekel, C.; Reznik, H. G.; Schollhorn, R. J. Solid State Chem. 1980, 34, 253-262. (25) Riekel, C.; Fischer, C. O. J. Solid State Chem. 1979, 29, 181-90. (26) Riekel, C.; Schollhorn, R. Mater. Res. Bull. 1976, 11, 369-376. (27) Paulus, W.; Katzke, H.; Schollhorn, R. J. Solid State Chem. 1992, 96, 162-168. (28) Chianelli, R. R.; Scanlon, J. C.; Raoj, B. M. L. J. Electrochem. Soc. 1978, 125, 1563. (29) Levy-Clement, C. Nato ASI Ser. B 1987, 172, 447-55. (30) Dahn, J. R.; Py, M. A.; Haering, R. R. Can. J. Phys. 1982, 60, 307. (31) Marcus, B.; Soubeyroux, J. L.; Touzain, P. NATO ASI Ser. B 1987, 172, 375-378. (32) Chabre, Y. Nato ASI Ser. B 1993, 181-192. (33) Ripert, M.; Pannetier, J.; Chabre, Y.; Poinsignon, C. Mater. Res. Soc. Proc. 1991, 210, 359.
10.1021/ja9819099 CCC: $15.00 © 1998 American Chemical Society Published on Web 10/09/1998
10838 J. Am. Chem. Soc., Vol. 120, No. 42, 1998 For example, in a pioneering study, Riekel and Schollhorn measured time-resolved neutron diffraction data during the intercalation of 2H-TaS2 by NH3(g) yielding a qualitative understanding into the intercalation process. However, the available levels of beam flux, while high by neutron standards, necessitated either very large sample sizes (∼15 g) or long acquisition times, making a thorough, quantitative study under varying reaction conditions of temperature, concentration, and particle size unfeasible. Moreover, because of the large incoherent scattering from hydrogen atoms by neutrons, the samples studied had to be highly deuterated, which is an expensive and not always achievable prerequisite for other intercalation reactions. Recently, McKelvy and co-workers have demonstrated elegantly that in situ high-resolution transmission electron microscopy (HRTEM) measurements can be performed during the intercalation of NH3 into TiS2 and the deintercalation of Hg from HgxTiS2 in specially constructed environmental cells. These studies have provided fascinating insights into these reactions at the molecular level.34-37 Paulus et al. used in situ X-ray diffraction to study the intercalation of solvated Cs+ ions into NbS2 single crystals and pressed powder electrodes.27 While the small quantities required for such experiments were a significant advance over the earlier neutron diffraction techniques, the cell design and geometry limited the application of this technique to electrochemical intercalation at moderate rates (time resolution ∼30 min per diffractogram). Even taking all these previous experiments into consideration we still have a fairly rudimentary understanding of the intimate mechanism of these reactions. The critical factors which control the rates of these reactions are still based on trial and error experiments. A schematic picture that is still commonly used to illustrate these reactions is shown in Figure 1a; undoubtedly this greatly oversimplifies the true picture. In recent years the technological and experimental advances in energy-dispersive powder diffraction with synchrotron X-ray sources have provided new possibilities for the solid-state kineticist.38-41 The markedly higher intensity (several orders of magnitude) over conventional laboratory X-ray sources allows the acquisition of good quality spectra from milligram samples on a time scale of seconds, making kinetic studies of fast intercalation reactions a realizable goal. The energy distribution of the X-rays (5-140 keV) is such that they are not significantly attenuated by a variety of materials suitable for cell windows, facilitating the construction of sealed sample holders. Moreover, the fixed geometry of this technique greatly simplifies the design of any sample environment. The less stringent space constraints in synchrotron X-ray diffractometers also allow construction of more elaborate sample cells which can accommodate a wider variety of reactants, such as single crystal or microcrystalline hosts, reacting with solvated or gas-phase guests, all within a sealed, dry, anaerobic sample environment. We have recently reported the construction and commissioning of an environmental cell for measuring time-resolved energy-dispersive X-ray diffraction data for fast intercalation reactions of potentially air(34) Mamedov, K. K.; Kerimav, I. G.; Konstryukov, V. N.; Guseinov, G. D. Russ. J. Phys. Chem. 1967, 41, 691. (35) Mckelvy, M.; Sidorov, M.; Marie, A.; Sharma, R.; Glaunsinger, W. Chem. Mater. 1995, 7, 1045-1046. (36) Mckelvy, M.; Sidorov, M.; Marie, A.; Sharma, R.; Glaunsinger, W. Chem. Mater. 1994, 6, 2233-2245. (37) Mckelvy, M. J.; Sharma, R.; Glaunsinger, W. S. Solid State Ionics 1993, 63-5, 369-377. (38) Barnes, P. Phase Transitions 1992, 39, 1-2. (39) Hausermann, D.; Barnes, P. Phase Transitions 1992, 39, 99-115. (40) Barnes, P.; Clark, S. M.; Hausermann, D.; Henderson, E.; Fentiman, C. H.; Muhamad, M. N.; Rashid, S. Phase Transitions 1992, 39, 117-128. (41) Sheridan, A. K.; Anwar, J. Chem. Mater. 1996, 8, 1042-1051.
EVans et al.
Figure 1. (a) Simple representation of the intercalation of a guest (Li+ ions) into a layered dichalcogenide host lattice (TiS2). (b) A more detailed breakdown of the various processes possible during intercalation as included in FIASCO2 simulations.
sensitive materials.42,43 Perhaps the most important aspect of this cell design is that it allows the recording of diffraction data of a wide variety of intercalation reactions under normal laboratory synthetic conditions. We report here the results of a detailed study of the rates of intercalation of the archetypal metallocene guest, cobaltocene {Co(Cp)2; Cp ) η-C5H5}, in a wide range of lamellar transition metal dichalcogenides ZrS2, 2H-SnS2, 2H-SnSe2, 2H-TaS2, 2HNbSe2, 1T-TaS2, and TiS2. The aim being to determine the rates of these reactions and hopefully gain an insight into their mechanism. Experimental Details Synthesis of Reactants. The syntheses of 2H-SnX2 (X ) S, Se) were based on procedures established by Al-Alamy and Balchin.44 Stoichiometric quantities of Sn powder (99.9%, Aldrich) and Se or S powder (99.9%, Aldrich) were weighed out into silica glass tubes that were evacuated to 10-3 Torr and sealed. The mixture was heated at the reaction temperature (560 °C for 2H-SnSe2 and 600 °C for 2HSnS2) for a week, ground with mortar and pestle, and annealed for another week. ZrS2 was synthesized from stoichiometric quantities of Zr powder (99.9%, Johnson Matthey) and S powder (99.99%, Aldrich) sealed in an evacuated silica tube and heated at 900 °C for a week. The powder was then annealed for another week, and small quantities of ZrS3, if present, were removed by sublimation. 2H- and 1T-TaS2 were synthesized by incorporating the ideas of Revelli, although to attain the desired polytypic purity a modified cooling procedure was (42) Clark, S. M.; Irvin, P.; Flaherty, J.; Rathbone, T.; Wong, H. V.; Evans, J. S. O.; O’Hare, D. ReV. Sci. Instrum. 1994, 65, 2210. (43) Wong, H. V.; Evans, J. S. O.; Clark, S. M.; O’Hare, D. J. Chem. Soc., Chem. Commun. 1994, 809. (44) Al-Alamy, F. A. S.; Balchin, A. A. J. Cryst. Growth 1977, 38, 221.
Intercalation of Cobaltocene by Layered Dichalcogenides adopted. TaCl5 (25.0 g) (Aldrich, 99.9%) was purified by vacuum sublimation at 10-2 Torr and 140 °C. A 12.0 g sample was loaded into an alumina boat and warmed to 200 °C over 90 min under a constant stream of H2S (approximately one bubble per second). Excess H2S was scrubbed by a combination of bleach and KMnO4/H+ bubblers. Sulfur was observed to form on the cold regions of the silica tube from around 160 °C. The furnace was maintained at 200 °C for 2 h, and then warmed to 900 °C for a further 3 h. The resulting black powder was heated to 200 °C under vacuum to remove any volatile impurities, then sieved to 60000
1.92 0.05 0.26
