A combined in situ X-ray absorption spectroscopy and X-ray diffraction study of the thermal decomposition of ammonium tetrathiotungstate

Abstract

The structural changes occurring during the thermal decomposition of ammonium tetrathiotungstate to form amorphous WS₃ and poorly crystalline WS₂ have been studied in situ using combined extended X-ray absorption fine structure (EXAFS) spectroscopy at the tungsten L_III-edge and X-ray diffraction. Data collected during isothermal decomposition at both 135 and 150 °C show that ammonium tetrathiotungstate decomposes to produce amorphous WS₃ without the formation of any intermediate phases. Decay curves of starting material and growth curves of product derived from both X-ray absorption data and diffraction data show that the two-phase approach to data analysis is appropriate. The fit of various simple kinetic models to the thermal decay curves is tested and it is found that the Prout-Tompkins expression describes the process very well. Heating ammonium tetrathiotungstate from 100 to 350 °C produces first amorphous WS₃ and finally disordered WS₂, a material of catalytic interest. The EXAFS data of this freshly prepared WS₂ are compared to those of crystalline 2H-WS₂. Debye-Waller factors are increased and occupation numbers are significantly reduced from those in the crystalline material for all atomic shells. This behaviour is compared to previous results obtained from poorly crystalline molybdenum disulfide and possible structural models suggested to account for the results of the first EXAFS study of the disordered WS₂.

References

1. R. Prins, V. H. J. De Beer and G. A. Somorjai, Catal. Rev.—Sci. Eng., 1989, 31, 1.
2. T. Weber, J. C. Muijsers, J. H. M. C. van Wolpot, C. P. J. Verhagen and J. W. Niemantsverdriet, J. Phys. Chem., 1996, 100, 14144.
3. B. K. Miremadi, K. Colbow and S. R. Morrison, J. Appl. Phys., 1997, 82, 2639 and references therein.
4. A. J. Jacobson, R. R. Chianelli, S. M. Rich and M. S. Whittingham, Mater. Res. Bull., 1979, 14, 1437.
5. J. J. Auborn, Y. L. Barberio, K. J. Hanson, D. M. Schleich and M. J. Martin, J. Electrochem. Soc., 1987, 134, 581.
6. K. Ramanathan and S. W. Weller, J. Catal., 1985, 95, 249.
7. S. P. A. Louwers and R. Prins, Jpn. J. Appl. Phys., 1993, 32, 457.
8. M. Remsikar, Z. Skraba, M. Regula, C. Ballif, R. Sanjines and F. Levey, Adv. Mater., 1998, 10, 246.
9. R. Tenne, M. Homyonfer and Y. Feldman, Chem. Mater., 1998, 10, 3225.
10. T. Osaki, H. Taoda, T. Horiuchi and H. Yamakita, React. Kinet. Catal. Lett., 1993, 51, 39.
11. J. Ramírez, P. Castillo, A. Benitez, A. Vasquez, D. Acosta and A. Lopéz-Agado, J. Catal., 1995, 158, 181.
12. K. Wilkinson, M. D. Merchán and P. T. Vasudevan, J. Catal., 1997, 171, 325.
13. G. Alonso, M. Del Valle, J. Cruz, A. Licea-Claverie, V. Petranovskii and S. Fuentes, Catal. Lett., 1998, 52, 55.
14. R. J. H. Voorhoeve and H. B. M. Wolters, Z. Anorg. Allg. Chem., 1970, 376, 165.
15. T. P. Prasad, E. Diemann and A. Müller, J. Inorg. Nucl. Chem., 1973, 35, 1895.
16. J. C. Wildervanck and F. Jellinek, Z. Anorg. Allg. Chem., 1964, 328, 309.
17. R. R. Chianelli, Int. Rev. Phys. Chem., 1982, 2, 127.
18. D. A. Rice, S. J. Hibble, M. J. Almond, K. A. Hassan Mohammad and S. P. Pearse, J. Mater. Chem., 1992, 2, 895.
19. S. J. Hibble, D. A. Rice, M. J. Almond, K. A. Hassan Mohammad, S. P. Pearse and J. R. Sagar, J. Mater. Chem., 1992, 2, 1237.
20. S. J. Hibble, R. I. Walton, D. M. Pickup and A. C. Hannon, J. Non-Cryst. Solids, 1998, 232–234, 434.
21. R. I. Walton, A. J. Dent and S. J. Hibble, Chem. Mater., 1998, 11, 3737.
22. K. S. Liang, J. P. de Neufville, A. J. Jacobson and R. R. Chianelli, J. Non-Cryst. Solids, 1980, 35, 1249.
23. K. S. Liang, S. P. Cramer, D. C. Johnston, C. H. Chang, A. J. Jacobson, J. P. de Neufville and R. R. Chianelli, J. Non-Cryst. Solids, 1980, 42, 345.
24. S. P. Cramer, K. S. Liang, A. J. Jacobson, C. H. Chang and R. R. Chianelli, Inorg. Chem., 1984, 23, 1215.
25. A. Müller, E. Diemann, E. Krickemeyer, H.-J. Walberg, H. Bögge and A. Armatage, Eur. J. Solid State Inorg. Chem., 1993, 30, 565.
26. Th. Weber, J. C. Muijsers and J. W. Niemantsverdriet, J. Phys. Chem., 1995, 99, 9194.
27. E. Diemann, Z. Anorg. Allg. Chem., 1977, 432, 127.
28. J. W. Couves, J. M. Thomas, D. Waller, R. H. Jones, A. J. Dent and G. N. Greaves, Nature, 1991, 345, 465.
29. S. R. Davis, A. V. Chadwick and J. D. Wright, J. Phys. Chem. B, 1997, 101, 9901.
30. M. Epple, G. Sankar and J. M. Thomas, Chem. Mater., 1997, 9, 3127.
31. I. J. Shannon, T. Maschmeyer, G. Sankar, J. M. Thomas, R. D. Oldroyd, M. Sheehy, D. Madill, A. D. Waller and R. P. Townsend, Catal. Lett., 1997, 23, 23.
32. B. S. Clausen, Catal. Today, 1998, 39, 293.
33. N. Binstead, J. W. Campbell, S. J. Gurman and P. C. Stephenson, EXCURV92, SERC Daresbury Laboratory, 1991.
34. G. Cliff and W. Lorimer, J. Microsc., 1975, 105, 205.
35. K. Sasvari, Acta Crystallogr., 1963, 16, 719.
36. R. R. Scott, A. J. Jacobson, R. R. Chianelli, W.-H. Pan, E. I. Stiefel, K. O. Hodgson and S. P. Cramer, Inorg. Chem., 1986, 25, 1461.
37. S. J. Hibble, D. A. Rice, D. M. Pickup and M. P. Beer, J. Chem. Soc., Faraday Trans., 1996, 92, 2131.
38. Report on the International Workshops on Standards and Criteria in XAFS in X-ray Absorption Fine Strucure, ed. S. S. Hasnain, Ellis Horwood, Chichester, 1991, p. 751.
39. F. C. Tompkins, Decomposition Reactions in Treatise on Solid State Chemistry, ed. N. B. Hannay, Plenum Press, New York, 1976, vol. 4, ch. 4. p. 193.
40. E. G. Prout and F. C. Tompkins, Trans. Faraday Soc., 1944, 40, 488.
41. W. J. Schutte, J. L. de Boer and F. Jellinek, J. Solid State Chem., 1987, 70, 207.
42. R. W. Joyner, K. J. Martin and P. Meehan, J. Phys. C: Solid State Phys., 1987, 20, 4005.
43. C. Calais, N. Matsubayashi, C. Geantet, Y. Yoshimura, H. Shimada, A. Nishijima, M. Lacroix and M. Breysse, J. Catal., 1998, 174, 130.
44. T. Shido and R. Prins, J. Phys. Chem. B, 1998, 102, 8426.
45. C. N. R. Rao and J. Gopalakrishan, New Directions in Solid State Chemistry, Cambridge University Press, Cambridge, 1997, p. 481.