Pressure dependence (10^-8–1000 mbar) of the vibrational spectra of CO chemisorbed on polycrystalline platinum studied by infrared–visible sum-frequency generation

Abstract

Picosecond infrared–visible sum-frequency generation (SFG) surface vibrational spectroscopy was applied for insitu monitoring of chemisorbed CO on a polycrystalline platinum foil at room temperature. The dependence of the SFG spectra on the CO gas-phase pressure was investigated in the range p_CO=10^-8–1000 mbar. From the measured SFG spectra, frequencies of the CO vibrationally resonant contribution were determined as a function of CO pressure. At low CO pressures (10^-8–10 mbar) a single vibrational band with center frequency in the range 2091–2099 cm^-1 was obtained which is characteristic of stretching vibrations of CO terminally adsorbed on Pt atoms of low-index (100)-, (110)- and (111)-type planes. At higher pressure (p_CO⩾50 mbar) the appearance of new “low-frequency’' CO surface species was observed which dominate the SFG spectra at CO pressures above 300 mbar. The low-frequency spectral feature was found to be completely reversible and reproducible with variation of the CO pressure. The pressure-dependent change in the SFG spectra suggests formation of Pt–(CO)₂ platinum carbonyl binary complexes at surface structures resulting from a reversible CO adsorbate-induced displacive reconstruction of the Pt substrate at high CO pressures.

References

1. See, for example, G. Ertl, in Catalysis Science and Technology 4, ed. J. R. Anderson and M. Boudart, Springer, New York, 1983; G. A. Somorjai, Introduction to Surface Chemistry and Catalysis, John Wiley and Sons, New York, 1994 and references therein.
2. H. Steininger, S. Lehwald and H. Ibach, Surf. Sci., 1982, 123, 264.
3. E. Schweizer, B. N. J. Persson, M. Tüshaus, D. Hodge and A. M. Bradshaw, Surf. Sci., 1989, 213, 49.
4. J. C. Campuzano, in The Chemical Physics of Solid Surfaces and Heterogeneous Catalysis, ed. D. A. King and D. P. Woodruff, Elsevier, Amsterdam, 1990, Vol. 3, Part A.
5. C. Klünker, M. Balden, S. Lehwald and W. Daum, Surf. Sci., 1996, 360, 104.
6. X. Su, P. S. Cremer, Y. R. Shen and G. A. Somorjai, Phys. Rev. Lett., 1996, 77, 3858.
7. Y. R. Shen, The Principles of Nonlinear Optics, John Wiley and Sons, New York, 1984; Y. R. Shen, Nature, 1989, 337, 519.
8. P. S. Cremer, B. J. McIntyre, M. Salmeron, Y. R. Shen and G. A. Somorjai, Catal. Lett., 1995, 34, 11.
9. G. A. Somorjai, Appl. Surf. Sci., 1997, 121/122, 1.
10. H. Härle, A. Lehnert, U. Metka, H.-R. Volpp, L. Willms and J. Wolfrum, Chem. Phys. Lett., 1998, 293, 26.
11. J. M. Thomas and W. J. Thomas, Principles and Practice of Heterogeneous Catalysis, VCH-Verlag, Weinheim, 1997.
12. H. Härle, K. Mendel, U. Metka, H.-R. Volpp, L. Willms and J. Wolfrum, Chem. Phys. Lett., 1997, 279, 275.
13. Y. R. Shen, in New Laser and Optical Investigation of Chemistry and Structure of Interfaces, ed. R. B. Hall and A. B. Ellis, Verlag Chemie, Weinheim, 1986.
14. J. Hunt, P. Guyot-Sionnest and Y. R. Shen, Chem. Phys. Lett., 1987, 133, 189.
15. Y. R. Shen, Solid State Commun., 1997, 102, 221.
16. See, for example, A. C. Eckbreth, Laser Diagnostics for Combustion Temperature and Species, Gordon and Breach, Amsterdam, 1996; J. Wolfrum, Lasers in Combustion: From Basic Theory to Practical Devices, 27th Symp. on Combustion (Int.), The Combustion Institute, Pittsburgh, 1998, pp. 1–41.
17. N. Sheppard and T. T. Nguyen, Adv. Infrared Raman Spectrosc., 1978, 5, 67.
18. A. Crossely and D. A. King, Surf. Sci., 1977, 68, 528; A. Crossely and D. A. King, Surf. Sci., 1980, 95, 131.
19. P. Hollins and J. Pritchard, Surf. Sci., 1979, 89, 489.
20. B. N. J. Persson and R. Ryberg, Phys. Rev. B, 1981, 24, 6954.
21. A. Ortega, F. M. Hoffman and A. M. Bradshaw, Surf. Sci., 1982, 119, 79.
22. H. Härle, A. Lehnert, U. Metka, H.-R. Volpp, L. Willms and J. Wolfrum, Appl. Phys. B, 1999, 68/3, 567.
23. R. G. Tobin, Surf. Sci., 1987, 183, 226.
24. R. K. Brandt, R. S. Sorbello and R. G. Greenler, Surf. Sci., 1992, 271, 605.
25. P. Hollins, Surf. Sci. Rep., 1992, 16, 51.
26. B. E. Hayden, K. Kretzschar, A. M. Bradshaw and R. G. Greenler, Surf. Sci., 1989, 149, 394; R. G. Greenler, K. D. Burch, K. Kretzschar, R. Klauser and A. M. Bradshaw, Surf. Sci., 1985, 152/3, 338; R. G. Greenler, F. M. Leibsle and R. S. Sorbello, Phys. Rev. B, 1985, 32, 8431.
27. U. Heiz, A. Sanchez, S. Abbet and W.-D. Schneider, J. Am. Chem. Soc., 1999, 121, 3214.
28. G. Longini and P. Chini, J. Am. Chem. Soc., 1976, 98, 7225.
29. A. Grushow and K. M. Ervin, J. Am. Chem. Soc., 1995, 117, 11612.
30. G. Schulze Icking-Konert, H. Handschuh, G. Ganteför and W. Eberhardt, Phys. Rev. Lett., 1996, 76, 1047.
31. A. Bandara, S. Dobashi, J. Kubota, K. Onda, A. Wada, K. Domen, C. Hirose and S. S. Kano, Surf. Sci., 1997, 387, 312.
32. A. Bandara, S. Katano, J. Kubota, K. Onda, A. Wada, K. Domen and C. Hirose, Chem. Phys. Lett., 1998, 290, 261.
33. U. Heiz, R. Sherwood, D. M. Cox, A. Kaldor and J. T. Yates, J. Phys. Chem., 1995, 99, 8730.
34. A. Sandel, J. Libuda, M. Bräumer and H.-J. Freund, Surf. Sci., 1996, 346, 108.
35. K. Wolter, O. Seiferth, J. Libuda, H. Kuhlenbeck, M. Bräumer and H.-J. Freund, Chem. Phys. Lett., 1997, 277, 513.