Abstract
The hydrogen isotope separation factor decreases with increasing overvoltage on mercury-like electrodes in acid solutions. This dependence qualitatively differs from that for the ratio between hydrogen evolution rates in light and heavy water, which increases with polarization. The reason for the difference is that the isotope separation factor depends on the kinetic isotopic effect (KIE) in two reaction stages: discharge and electrochemical desorption. Experimental data show that a decrease in KIE with potential in the latter stage outweighs the increase in KIE in the former. The KIE decreases in the desorption reaction because this process is activationless; therefore, there is no potential dependence of the relative contribution made by vibrationally excited states of the product in this case, i.e. no dependence that is responsible for the increase in KIE at the discharge stage. The same factor has no effect on KIE for a barrierless discharge, which also decreases with increasing overvoltage. Thus, all experimentally observed dependences of KIE on potential are explained in the framework of a unified approach.
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REFERENCES
Bunakova, L.V., Kriksunov, L.B., and Tsionskii, V.M., Elektrokhimiya, 1992, vol. 28, p. 275.
Bockris, J.O'M. and Srinivasan, S., J. Electrochem. Soc., 1964, vol. 111, p. 844.
Krishtalik, L.I., Elektrokhimiya, 1970, vol. 6, p. 1456.
Albery, W.J., in Progress in Reaction Kinetics, Porter, G., Ed., 1967, vol. 4, p. 353.
Spravochnik khimika (Handbook of Chemist), Nikol'skii, B.P., Ed., Moscow: Khimiya, 1966, vol. 1.
Post, B. and Hiskey, C.F., J. Am. Chem. Soc., 1950, vol. 72, p. 4203.
Post, B. and Hiskey, C.F., J. Am. Chem. Soc., 1951, vol. 73, p. 161.
Rome, M. and Hiskey, C.F., J. Am. Chem. Soc., 1954, vol. 76, p. 5207.
Drucker, C., Trans. Faraday Soc., 1937, vol. 33, p. 660.
Gold, V. and Lowe, B.M., Trans. Faraday Soc., 1969, vol. 65, p. 3037.
CRC Handbook of Chemistry and Physics, Boca Raton: CRC, 1996.
Bell, R., The Proton in Chemistry, London: Chapman and Hall, 1973.
Melander, L. and Saunders, W., Reaction Rates of Isotopic Molecules, New York: Wiley, 1980.
Krishtalik, L.I., Elektrokhimiya, 1979, vol. 15, p. 435.
Krishtalik, L.I., Mertz, E.L., and Topolev, V.V., in Electron and Ion Transfer in Condensed Media, Kornyshev, A.A., Tosi, M., and Ulstrup, J., Eds., Singapore: World Scientific, 1997, p. 277.
Tsionskii, V.M. and Krishtalik, L.I., Elektrokhimiya, 1969, vol. 5, p. 1184.
Krishtalik, L.I., Biochim. Biophys. Acta, 2000, vol. 1458, p. 6.
Krishtalik, L.I., Bunakova, L.V., and Shumskaya, S.E., Elektrokhimiya, 1998, vol. 34, p. 1354.
Krishtalik, L.I., Elektrokhimiya, 1991, vol. 27, p. 303.
Krishtalik, L.I., Elektrodnye reaktsii: Mekhanizm elementarnogo akta (Electrode Reactions: The Mechanism of an Elementary Act), Moscow: Nauka, 1979.
Tsionskii, V.M., Cand. Sci. (Chem.) Dissertation, Moscow: Frumkin Inst. of Electrochem., 1969.
Potapova, E.N., Krishtalik, L.I., and Bagotskaya, I.A., Elektrokhimiya, 1974, vol. 10, p. 49.
Potapova, E.N., Krishtalik, L.I., and Bagotskaya, I.A., Elektrokhimiya, 1974, vol. 10, p. 53.
Benderskii, V.A. and Grebenshchikov, S.Yu., J. Electroanal. Chem., 1994, vol. 375, p. 29.
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Krishtalik, L.I. Isotope Separation Factor and Kinetic Isotopic Effect of the Hydrogen Evolution Reaction. Russian Journal of Electrochemistry 37, 102–106 (2001). https://doi.org/10.1023/A:1009092015225
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DOI: https://doi.org/10.1023/A:1009092015225