Ionics

, Volume 3, Issue 1–2, pp 110–116 | Cite as

Electrochemical promotion of ammonia decomposition over Fe catalyst films interfaced with K+- & H+- conductors

  • G. E. Pitselis
  • P. D. Petrolekas
  • C. G. Vayenas
Article

Abstract

The electrochemical promotion of the ammonia decomposition reaction over Fe catalyst films interfaced with K2YZr(PO4)3, a K+-conductor, and CaZr0.9In0.1O3−a, a H+-conductor, was investigated at temperatures 500–600 °C. At the higher temperatures, the catalytic rate was found to decrease significantly and reversibly upon decreasing the catalyst potential, VWR, i.e., upon pumping K+ or H+ to the Fe surface. The effect of potassium was more pronounced than that of protons leading to almost complete poisoning of the reaction. At the lower temperatures, it was found that electrochemical supply of moderate amounts of potassium causes an enhancement in the catalytic rate while higher amounts poison the reaction.

The study reports, for the first time, electrochemical promotion over a Fe catalyst and shows that K+-conductors can also be used to induce the effect of Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA). The effect of backspillover potassium ions and protons on the catalytic activity is discussed in terms of the theory of electrochemical promotion by considering the effect of varying catalyst work function on the coverages and chemisorptive bond strengths of NH3, N and H. The results show the possibility of using electrically promoted catalyst pellets to alter the performance of industrial reactions.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. [1]
    C.G. Vayenas, S. Bebelis and S. Neophytides, J.Phys. Chem.92, 5083 (1988).CrossRefGoogle Scholar
  2. [2]
    C.G. Vayenas, S. Bebelis, I.V. Yentekakis and H.-G. Lintz, Catal. Today11, 303 (1992) and references therein.CrossRefGoogle Scholar
  3. [3]
    C.G. Vayenas, M.M. Jaksic, S. Bebelis and S. Neophytides, in: Modern Aspects of Electrochemistry,No 29, (J.O 'M. Bockris, B.E. Conway and R.E. White, Eds) Plenum Press, New York, 1996) pp. 57–202 and references therein.Google Scholar
  4. [4]
    J.O. 'M Bockris and Z. S. Minevski, Electrochimica Acta39, 1471 (1994).CrossRefGoogle Scholar
  5. [5]
    J. Pritchard, Nature343, 592 (1990).CrossRefGoogle Scholar
  6. [6]
    B. Crzybowska-Swierkosz and J. Haber in Annual Reports on the Progress of Chemistry, Vol.91 (The Royal Society of Chemistry, Cambridge, U.K., 1994) pp. 395–439Google Scholar
  7. [7]
    I.R. Harkness and R.M. Lambert, J. Catal.152, 211 (1995).CrossRefGoogle Scholar
  8. [8]
    S. Bebelis and C.G. Vayenas, J. Catal.118, 125 (1989).CrossRefGoogle Scholar
  9. [9]
    I.V. Yentekakis, G. Moggridge, C.G. Vayenas and R.M. Lambert, J. Catal.146, 292 (1994).CrossRefGoogle Scholar
  10. [10]
    P.D. Petrolekas, S. Brosda and C.G. Vayenas, J. Electrochem. Soc., in press.Google Scholar
  11. [11]
    M. Makri, A. Buekenhoudt, J. Luyten and C.G. Vayenas, Ionics2, 282 (1996).Google Scholar
  12. [12]
    S. Neophytides, D. Tsiplakides, O. Enea, M.M. Jaksic and C.G. Vayenas, J. Electrochem. Soc. (in press).Google Scholar
  13. [13]
    I.V. Yentekakis and C.G. Vayenas, J. Catal.149, 238 (1994).CrossRefGoogle Scholar
  14. [14]
    C. Pliangos, I.V. Yentekakis, S. Ladas, and C.G. Vayenas, J. Catal.159, 189 (1996).CrossRefGoogle Scholar
  15. [15]
    P.D. Petrolekas, S. Balomenou and C.G. Vayenas, J. Electrochem. Soc., submitted.Google Scholar
  16. [16]
    S. Neophytides, D. Tsiplakides, P. Stonehart, M.M. Jaksic and C.G. Vayenas, Nature (London)370, 45 (1994).CrossRefGoogle Scholar
  17. [17]
    S. Neophytides and C.G. Vayenas, J. Phys. Chem.99, 17063 (1995).CrossRefGoogle Scholar
  18. [18]
    S. Ladas, S. Kennou, S. Bebelis and C.G. Vayenas, J. Phys. Chem.97, 8845 (1993).CrossRefGoogle Scholar
  19. [19]
    C.G. Vayenas, S. Bebelis, and S. Ladas, Nature (London)343, 625 (1990).CrossRefGoogle Scholar
  20. [20]
    M. Makri, C.G. Vayenas, S. Bebelis, K.H. Besocke, and C. Cavalca, Surface Science369, 351 (1996).CrossRefGoogle Scholar
  21. [21]
    U. Guth, B. Löscher, P. Schmidt, H. Wulff and H.-H. Möbius, Solid State Ionics51, 183 (1992).CrossRefGoogle Scholar
  22. [22]
    U. Guth, S. Brosda, B. Loescher, A. Simmich, P. Schmidt, H.-H. Möbius, Material Science Forum76, 137 (1991).Google Scholar
  23. [23]
    Ch. Karavasilis, S. Bebelis, and C.G. Vayenas, J. Catal.160, 205 (1996).Google Scholar
  24. [24]
    I.R. Harkness, C. Hardacre, R.M. Lambert, I.V. Yentekakis and C.G. Vayenas, J. Catal.160, 19 (1996).CrossRefGoogle Scholar
  25. [25]
    W. Zipprich, H.-D. Wiemhöfer, K. Vohrer, and, W. Göpel, Ber. Bunsenges. Phys. Chem.99, 1406 (1995).Google Scholar
  26. [26]
    S. B. Lee, M. Weiss and G. Ertl, Surface Science108, 357 (1981)CrossRefGoogle Scholar
  27. [27]
    Z. Kowalcyk, J. Sentek, S. Jodzis, M. Muhler and O. Hinrichsen, J. Catal.169, 407 (1997) and references therein.Google Scholar

Copyright information

© IfI - Institute for Ionics 1997

Authors and Affiliations

  • G. E. Pitselis
    • 1
  • P. D. Petrolekas
    • 1
  • C. G. Vayenas
    • 1
  1. 1.Department of Chemical EngineeringUniversity of PatrasPatrasGreece

Personalised recommendations