SERS study of the electrochemical reduction of pyrazine on a silver electrode

Abstract

The electrochemical reduction of pyrazine (pz) on a silver electrode from a 1.0 M KBr solution has been investigated by surface enhanced Raman scattering (SERS). New bands from products of reduced pyrazine were observed at potentials more negative than -900 mV (vs. SCE). The main product is believed to be the 1,4-dihydropyrazine cation (DHPz⁺). The reduction is not completly reversible. It is clear from the observed spectroscopic and electrochemical data that some of the DHPz⁺ was not re-oxidized when the potential scan was switched to positive values. This DHPz⁺ (or one of its derivatives with similar structure) remained trapped on the electrode surface even at potentials more positive than the point of zero charge (pzc) of silver in this medium. It is proposed that the cation binds to adsorbed halide at potentials more positive than the pzc. The presence of reduced pyrazine products at potentials more positive than the pzc can lead to misinterpretations of the SER spectrum of pyrazine.

References

1. A. G. Brolo and D. E. Irish, Z. Naturforsh., Teil A, 1995, 50, 274.
2. M. Moskovits, D. P. DiLella and K. J. Maynard, Langmuir, 1988, 4, 67.
3. G. R. Erdheim, R. L. Birke and J. R. Lombardi, Chem. Phys. Lett., 1980, 69, 495.
4. V. M. Hallmark and A. Campion, J. Chem. Phys., 1986, 84, 2933.
5. F. Zhong and G. Wu, J. Mol. Struct., 1994, 324, 233.
6. J. Thietke, J. Billmann and A. Otto, Dynamics on Surfaces, Proceedings of the XV II Jerusalem Symposium on Quantum Chemistry and Biochemistry, D. Reidel, Dordrecht, 1984, p. 345.
7. Y. Huang and G. Wu, Spectrochim. Acta, Part A, 1990, 46, 377.
8. R. Dornhaus, M. B. Long, R. E. Benner and R. K. Chang, Surf. Sci., 1980, 93, 240.
9. A. G. Brolo and D. E. Irish, J. Electroanal. Chem., 1996, 414, 183.
10. L. N. Klatt and R. L. Rouseff, J. Am. Chem. Soc., 1972, 94, 7295.
11. J. Swartz and F. C. Anson, J. Electroanal. Chem., 1980, 114, 117.
12. A. G. Brolo, D. E. Irish and B. D. Smith, J. Mol. Struct., 1996, in the press.
13. D. Lin-Vien, N. B. Colthup, W. G. Fateley and J. G. Grasselli, The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules, Academic Press, Toronto, 1991.
14. D. A. Guzonas, D. E. Irish and G. F. Atkinson, Langmuir, 1990, 6, 1102.
15. D. J. Rogers, S. D. Luck, D. E. Irish, D. A. Guzonas and G. F. Atkinson, J. Electroanal. Chem., 1984, 167, 237.
16. Z. Deng and D. E. Irish, J. Phys. Chem., 1994, 98, 9371.
17. D. A. Guzonas, D. E. Irish and G. F. Atkinson, Langmuir, 1989, 5, 787.
18. K. Bange, B. Straehler, J. K. Sass and R. Parsons, J. Electroanal. Chem., 1987, 229, 87.
19. G. Valette and R. Parsons, J. Electroanal. Chem., 1985, 191, 377.
20. J. E. Pemberton and M. M. Girand, J. Electroanal. Chem., 1987, 217, 79.
21. R. de Levie, J. Electroanal. Chem., 1990, 281, 1.