Electrochemical promotion of catalyst surfaces deposited on ionic and mixed conductors
- 37 Downloads
The effect of non-Faradaic electrochemical modification of catalytic activity (NEMCA) or electrochemical promotion (EP) was investigated on Pt films deposited on Y2O3-stabilized-ZrO2 (YSZ), an O2− conductor, TiO2, a mixed conductor, and Nafion 117 solid polymer electrolyte (SPE), a H+ conductor and also on Pd films deposited on YSZ and β″-Al2O3 a Na+ conductor. Four catalytic systems were investigated, i.e. C2H6 oxidation on Pt/YSZ, C2H4 oxidation on Pd/YSZ and Pd/β″-Al2O3, C2H4 oxidation on Pt/TiO2 and H2 oxidation on Pt/Nafion 117 in contact with 0.1 M aqueous KOH solution.
In all cases pronounced and reversible non-Faradaic electrochemical modification of catalytic rates was observed with catalytic rate enhancement up to 2000% and Faradaic efficiency values up to 5000.
All reactions investigated exhibit a pronounced electrophobic behaviour which is due to the weakening of chemisorptive oxygen bond at high catalyst potentials. Ethane oxidation, however, also exhibits electrophilic behaviour at low potentials due to weakened binding of carbonaceous species on the surface.
The general features of the phenomenon are similar for all four cases presented here showing that the NEMCA effect is a general, electrochemically induced, promoting catalytic phenomenon not depending on the reaction and the type of supporting electrolyte.
KeywordsTiO2 C2H4 Oxidation Solid Polymer Electrolyte Catalytic Rate Chemisorptive Oxygen
Unable to display preview. Download preview PDF.
- C.G. Vayenas, S. Bebelis, I.V. Yentekakis and H.G. Lintz, Catalysis Today, Elsevier, Amsterdam,11(3), 303–442 (1992).Google Scholar
- I.V. Yentekakis and C.G. Vayenas, J. Catal.111, 170 (1988).Google Scholar
- C.G. Vayenas, S. Bebelis, S. Neophytides and I.V. Yentekakis, Appl. Phys.A49, 95 (1989).Google Scholar
- C.G. Vayenas, S. Bebelis, I.V. Yentekakis, P. Tsiakaras and H. Karasali, Platinum Metals Rev.34 (3), 122 (1990).Google Scholar
- C.G. Vayenas, S. Bebelis and C. Kyriazis, Chemtech21, 500 (1991).Google Scholar
- C.G. Vayenas, S. Bebelis, I.V. Yentekakis and S. Neophytides, Solid State Ionics53–56, 97 (1992).Google Scholar
- S. Bebelis and C.G. Vayenas, J. Catal.138, 570, (1992);138, 588 (1992).Google Scholar
- H. Alqahtany, P. Chiang, D. Eng and M. Stoukides, Catal. Letters13, 289 (1992).Google Scholar
- T.I. Politova, V.A. Sobyanin and V.D. Belyaev, React. Kinet. Lett.41, 321 (1990).Google Scholar
- U. Vöhrer, Ph.D. Thesis, Universität Tübingen, 1992.Google Scholar
- Y. Jiang, A. Kaloyannis and C.G. Vayenas, Electrochimica Acta38, 17, 2533–2539 (1993).Google Scholar
- H. Takenaka and E. Torikai, Kokai Tokkyo Koho (Japan Patent), 55-38934 (1980).Google Scholar
- J.O.'M. Bockris and A.K.N. Reddy in “Modern Electrochemistry”, Vol. 2, Plenum Press, New York (1970).Google Scholar
- B.E. Conway, in Electrodes of Coductive Metallic Oxides (ed. Trasatti, S.) Ch. 9 (Elsevier, Amsterdam 1981).Google Scholar
- J.O.M'. Bockris and A.K.N. Reddy, in Modern Electrochemistry (Plenum, New York, 1973).Google Scholar
- J.O.M'. Bockris and S.U.M. Khan, in Surface Electrochemistry, a Molecular Level Approach Ch. 3 (Plenum, New York, 1993).Google Scholar
- B.E. Conway and B.V. Tilak, Adv. Catal.38, 1–123 (1992).Google Scholar
- C. Pliangos, I.V. Yentekakis, S. Ladas and C.G. Vayenas, J. Catalysis, in press (1995)Google Scholar