Effect of electrode material on the oxidation of H2 at the metal-Sr0.995Ce0.95Y0.05O2.970 interface

The effect of electrode material on the electrode kinetics of a metal-proton conductor interface has been investigated in a quasi point-contact configuration for four metals: Ni, Ag, Au and Pt. The current-voltage behaviour depends on the nature of the electrode, the hydrogen partial pressure and on temperature. For all systems studied, the anodic part of the polarisation curves displayed limiting current behaviour. For Pt at low anodic polarisation, an additional process determines the overall reaction rate. The apparent reaction order (q(app)) is found to be strongly dependent on electrode type, suggesting that the reaction mechanism is decisively determined by the electrode, rather than by electrolyte surface. The electrocatalytic activity of the metal tested has been classified according to the limiting current density in a humidified atmosphere of N-2-1% H-2. The highest i(lim) has been detected for Ni, followed by Pt, An and Ag. (C) 2000 Elsevier Science B.V. All rights reserved.