Electrochemical promotion of environmentally important catalytic reactions
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Abstract
The performance of conventional heterogeneous metal catalysts may be enhanced by the addition of so-called promoter species that are used to modify the intrinsic metal surface chemistry with respect to activity and/or selectivity. Electrochemical methods provide an alternative, radically different and uniquely efficacious method of catalyst promotion. Substantial and reversible changes in catalyst perfomance can be induced by back-spillover ions pumped from a solid electrolyte to the surface of a catalytically active electrode: one hasin situ control of the working catalyst.
Studies of the electrochemical promotion of NO reduction over Pt films supported on β″-alumina (a sodium ion conductor) demonstrate that major enhancements in activity are possible when Na is pumped to the catalyst surface. We have examined the NO+CO reaction and the reaction of NO with propene. Both reactions are relevant to control of automotive and other emissions, and both exhibit strong electrochemical promotion. By simulating lean-burn engine conditions, we have also demonstrated that EP of a Pt catalyst very substantially enhances the ability of NO to oxidise propene in an oxygen-rich atmosphere. Reaction kinetic data obtained as a function of catalyst potential, temperature and gas composition indicate that Na increases the strength of NO chemisorption relative to CO or propene, a process that is accompanied by weakening of the N-O bond, thus facilitating NO dissociation, which is the critical reaction-initiating step. XP spectroscopy under the appropriate conditions of temperature and catalyst potential confirms that the mode of operation of the elctrochemically promoted Pt film does indeed involve reversible pumping of Na to or from the solid electrolyte.
Keywords
Propene Chemisorption Solid Electrolyte Active Electrode Engine ConditionPreview
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7. References
- [1]C.G. Vayenas, S. Bebelis, I.V. Yentekakis, and H.G. Lintz, in “Catalysis Today”, Vol. 11, No 3, p. 303. Elsevier, Amsterdam, 1992.Google Scholar
- [2]S.G. Neophytides, D. Tsiplakides, P. Stonehart, M.M. Jaksic and C.G. Vayenas, Nature370, 45 (1994).CrossRefGoogle Scholar
- [3]J. A. Rodriguez and D. W. Goodman, Surf. Sci. Reports14, 1 (1991).Google Scholar
- [4]Y. O. Park, W. F. Banholzer and R. I. Masel, Surf. Sci.155, 341 (1985).CrossRefGoogle Scholar
- [5]W. F. Banholzer, R. E. Parise and R. I. Masel, Surf. Sci.155, 653 (1985).CrossRefGoogle Scholar
- [6]D'Arcy Lorimer and A. T. Bell, J. Catal.59, 223 (1979).CrossRefGoogle Scholar
- [7]B. A. Banse, D. T. Wickham and B. E. Koel, J. Catal.119, 238 (1989).CrossRefGoogle Scholar
- [8]R. L. Klein, S. Schwartz and L. D. Schimdt, J. Phys. Chem.89, 4908 (1985).CrossRefGoogle Scholar
- [9]D. N. Belton and S. J. Scmieg J. Catal138, 70 (1992).CrossRefGoogle Scholar
- [10]D. N. Belton and S. J. Scmieg J. Catal.144, 9 (1993).Google Scholar
- [11]S. E. Oh., G. B. Fischer, J. E. Carpenter and D. W. Goodman J. Catal.100, 360 (1986).CrossRefGoogle Scholar
- [12]A. Obuchi, A. Ohi, M. Nakamura, A. Ogata, K. Mizuno and H. Ohuchi, Appl.Catal.B, Environmental,2, 71 (1993).CrossRefGoogle Scholar
- [13]J.R. Hardee and J.W. Hightower, J.Catal.86, 137 (1984).CrossRefGoogle Scholar
- [14]S. Naito and M. Tanimoto, Chem. Lett.1935 (1993).Google Scholar
- [15]R. Burch, P.J. Millington, A.P. Walker Appl. Catal. B: Environmental.4, 65. (1994)CrossRefGoogle Scholar
- [16]T. Miyadera and K. Yoshida, Chem. Lett. (1993) p.1483.Google Scholar
- [17]H. Hamada, Y. Kintaichi, M. Sasaki, T. Ito, M. Tabata, Appl. Catal.75, L1 (1991).Google Scholar
- [18]C.G. Vayenas, S. Bebelis, S. Neophytides and I.V. Yentekakis, Appl. Phys.A49, 95 (1989).Google Scholar
- [19]I.V. Yentekakis, S. Neophytides and C.G. Vayenas, J. Catal.111, 152 (1988).Google Scholar
- [20]I.V. Yentekakis and S. Bebelis, J. Catal.137, 278 (1992)CrossRefGoogle Scholar
- [21]C.G. Vayenas, S. Bebelis and M. Despotopoulou, J. Catal. 128, 415 (1991).CrossRefGoogle Scholar
- [22]I.V. Yentekakis, G.D. Moggridge, G.D. Moggridge, C.G. Vayenas and R.M. Lambert, J. Catal.146 (1994) 292.CrossRefGoogle Scholar
- [23]N.D. Lang, S. Holloway and J.K. Norskov, Surface Science150, 24 (1985).CrossRefGoogle Scholar
- [24]I. R. Harkness and R.M. Lambert,in preparation.Google Scholar
- [25]G. Pirug and H.P. Bonzel, J. Catal.50, 64 (1977).CrossRefGoogle Scholar
- [26]I. R. Harkness and R.M. Lambert, J. Catal.152, 211 (1995).CrossRefGoogle Scholar
- [27]N.R. Avery, N.S. Sheppard, Proc. Roy. Soc. Lond.A405, 1 (1986).Google Scholar
- [28]R.J. Koestner, J.C. Frost, P.C. Stair, M.A. VanHove, G.A. Somorjai, Surf. Sci.116, 85 (1982).CrossRefGoogle Scholar
- [29]M. Salmeron, G.A. Somorjai, J. Phys. Chem.86, 341 (1982).CrossRefGoogle Scholar