Electrode kinetics of hydrogen oxidation on nickel/YSZ cermet anodes

The hydrogen oxidation reaction on nickel/zirconia cermet electrodes (Ni/YSZ cermet electrodes) was investigated as a function of potential and temperature at different partial pressures of the reactants. At 726 degrees C the apparent reaction order for hydrogen m(H) is close to 0.5 and is nearly independent of the electrode potential The activation energy amounts to 145 kJ/mol at rest potential. The apparent charge transfer coefficient in the temperature range from 726 degrees C to 845 degrees C is approximately 0.7, independent of temperature. This result was obtained from both the Arrhenius plots of the current density at constant overpotentials and from the Tafel analysis of the current-potential curves. Therefore it is concluded that a charge transfer reaction is limiting the reaction rate at these temperatures.