Chem. Mater. 1999, 11, 691-697
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Reaction of Metal, Carbide, and Nitride of Tungsten with Hydrogen Peroxide Characterized by 183W Nuclear Magnetic Resonance and Raman Spectroscopy Hitoshi Nakajima and Tetsuichi Kudo Institute of Industrial Science, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106-8558, Japan
Noritaka Mizuno* Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Received July 30, 1998. Revised Manuscript Received November 18, 1998
Chemical species formed by reactions of tungsten metal, carbide, and nitride with hydrogen peroxide were characterized by multinuclear nuclear magnetic resonance and Raman spectroscopy and gas chromatography. The results not only showed formation of previously known tetraperoxoditungstate, but also strongly suggested formation of diperoxomonotungstate, its protonated form, monoperoxomonotungstate, and diperoxoditungstate. Carbon in tungsten carbide was only oxidized, and oxalate ion, carbon monoxide, and carbon dioxide were produced. On the other hand, both oxidation and hydrolysis of nitrogen were observed for tungsten nitride. It was suggested that the difference of reactivity was explained by the ionicity of tungsten-heteroatom bond.
Introduction Carbides or nitrides of group IV to VI transition metals have both metal-metal and metal-carbon or metal-nitrogen bonds and are called interstitial compounds. These interstitial compounds have high thermal and chemical stability and electrical conductivity. Hence, the compounds have been used as hard metallurgical coatings,1 catalysts,2 and especially recently, diffusion barriers in semiconductor technology.3,4 The preparation methods of thin films or ultrafine particles, by chemical vapor deposition (CVD)5 and ion implanting,6 and surface states of the materials were also studied. On the other hand, carbides and nitrides of these transition metals form peroxo complexes by the reaction with hydrogen peroxide, and they can be applied to inorganic precursors to proton conductors,7 photoresists,8 electrochromic devices,9 and metal oxides of tungsten bronzes10a and vanadium dioxide.10b The in(1) Kaloyeros, A. E.; Williams, W. S.; Brown, F. C.; Greene A. E. Phys. Rev. B 1988, 37, 771. (2) Ramanathan, S.; Oyama, S. T. J. Phys. Chem. 1995, 99, 16365. (3) Oyama, S. T. The Chemistry of Transition Metal Carbides and Nitrides; Blackie Academic & Professional: London, 1996; Pogger, H. B. Electronic Materials Chemistry; Marcel Dekker: New York, 1996. (4) Kolawa, E.; So, F. C. T.; Tandon, J. L.; Nicolet, M.-A. J. Electrochem. Soc. 1987, 134, 1759; Appelbaum, A.; Murarka, S. P. J. Vac. Sci. Technol. A 1986, 4, 637. (5) Nagai, M.; Kishida, K. Appl. Surf. Sci. 1993, 70/71, 759; Raaijmakers, I. J.; Yang, J. Appl. Surf. Sci. 1993, 73, 31. (6) Palmetshofer, L.; Rodhammer, P. Nucl. Instr. Methods B 1993, 80/81, 340; Sioshansi, P. Mater. Sci. Eng. 1987, 90, 373. (7) Okamoto, H.; Yamanaka, K.; Kudo, T. Mater. Res. Bull. 1986, 21, 551; Hibino, M.; Nakajima, H.; Kudo, T.; Mizuno, N. Solid State Ionics 1997, 100, 212. (8) Kudo, T.; Ishikawa, A.; Okamoto, H.; Miyauchi, K.; Murai, F.; Mochiji, K.; Umezaki, H. J. Electrochem. Soc. 1987, 134, 2607.
vestigation of solution chemistry is important for not only the better understanding of the processes but also the peroxo chemistry of group IV to VI transition metals. Recently, we reported that the mononuclear and dinuclear tungsten peroxo complexes were formed by the reaction of tungsten metal with hydrogen peroxide11 and that peroxotungstates prepared by the reaction of an R-WC with hydrogen peroxide can be precursors to proton conductors.7 Peroxo complexes of group IV to VI transition metals were extensively studied by Griffith,12 Stomberg,13 Thompson,14 and others,15 since 1960s. Reviews of tungsten, molybdenum, chromium, and vanadium, were also reported.16 Recently, the peroxo complexes have also attracted attention as oxidants or catalysts for the oxidation of organic substrates with hydrogen peroxide including biological applications.17 (9) Li, Y. M.; Aikawa, Y.; Kishimoto, A.; Kudo, T. Electrochim. Acta 1994, 39, 807. (10) (a) Tatsumi, K.; Hibino, M.; Kudo, T. Solid State Ionics 1997, 96, 35. (b) Takahashi, I.; Hibino, M.; Kudo, T. Jpn. J. Appl. Phys. 1996, 35, L438. (11) Nakajima, H.; Kudo, T.; Mizuno, N. Chem. Lett. 1997, 693. (12) (a) Campbell, N. J.; Dengel, A. C.; Edwards, C. J.; Griffith, W. P. J. Chem. Soc., Dalton Trans. 1989, 1203. (b) Griffith, W. P.; Parkin, B. C.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 1995, 3131 and refs. therein. (13) (a) Stomberg, R. J. Less-Common Met. 1988, 143, 363. (b) Stomberg, R. Acta Chem. Scand. A 1985, 39, 507. (c) Stomberg, R.; Olson, S. Acta Chem. Scand. A 1985, 39, 79. (14) (a) Ghiron, A. F.; Thompson, R. C. Inorg. Chem. 1988, 27, 4766. (b) Ghiron, A. F.; Thompson, R. C. Inorg. Chem. 1990, 29, 4457 and refs. therein. (15) For example, Nardello, V.; Marko, J.; Vermeersch, G.; Aubry, J. M. Inorg. Chem. 1995, 34, 4950; Reynolds, M. S.; Butler, A. Inorg. Chem. 1996, 35, 2378. (16) (a) For peroxotungstates, molybdates, or chromates, Dickman, M. H.; Pope, M. T. Chem. Rev. 1994, 94, 569. (b) For peroxovanadates, Butler, A.; Clague, M. J.; Meister, G. E. Chem. Rev. 1994, 94, 625.
10.1021/cm980544o CCC: $18.00 © 1999 American Chemical Society Published on Web 02/24/1999
692 Chem. Mater., Vol. 11, No. 3, 1999
Nakajima et al.
Table 1. Data of Structure, Particle Size, Elemental Analysis, and pH and the Ratio of Amount of Tungsten Reacted tungsten compound
structure
elemental analysis of tungsten, wt %a
metal carbide nitride
cubic W hexagonal R-WC amorphous
100 (100) 93 (94) 96 (96b)
pH of reaction solution initial final 3.05 3.38 2.46
0.22 0.18 0.47
amount of tungsten compounds reacted, wt %
solution
100 100 99
(I) (II) (III)
a Numbers in parentheses were theoretical amounts of tungsten in tungsten compounds. b Calculated assuming that the composition of tungsten nitride is W2N.
However, little is known of the peroxo tungsten complexes formed at low pH and at equilibrium. The variety of ionicity of the bonds between metal and nonmetal atoms in the interstitial compounds was pointed out by Toth18 and confirmed by X-ray photoelectron spectroscopy (XPS).19 The investigation of how the ionicity influences the chemical species of nonmetal elements formed by the reactions with hydrogen peroxide is also interesting. In this paper, we investigated the species formed by reactions of carbide, nitride, and metal of tungsten with hydrogen peroxide by multinuclear nuclear magnetic resonance (NMR) and Raman spectroscopy and the gasphase analysis and attempted to clarify the reaction mechanism.20 Experimental Section Reagents and K2W(O2)4. Metal (Mitsuwa Chemical Company Ltd., particle size ∼1 µm), carbide (Rare Metallic, particle size ∼1 µm), and nitride (High Purity Chemicals, particle size ∼100 µm) of tungsten and aqueous hydrogen peroxide (30 wt %, Junsei Chemical Company Ltd.) were commercially obtained and used without further purification. The content of W in each sample was determined by inductively coupled plasma (ICP) analysis after the sample was dissolved in an acidic solution of hydrogen peroxide. The data of the structure and elemental analysis for starting materials are summarized in Table 1. The structures of metal and carbide of tungsten consisted of single phases of cubic W and hexagonal R-WC, respectively. Tungsten nitride was amorphous. The atomic ratio of N/W was 0.58 and it was confirmed that the content of hydrogen was
