The effect of electrochemical current pumping on the work function of solid electrolyte supported catalysts

Oxygen-ion current pumping experiments were performed on a platinum electrode catalyst in a solid electrolyte electrochemical cell in the temperature range 688-723 K. The electrode overpotential and extraction potential in the presence of air were both monitored during the experiments. The transient behaviour of the catalyst work function was found to be complex and was explained in terms of the both the adsorption of spillover oxygen onto, and the absorption of spillover oxygen into, the Pt surface. Electrochemical oxygen supply appears to be more selective for absorbed oxygen formation than gas phase oxygen supply. At steady state the Pt catalysts failed to exhibit the direct equality between the extraction potential and applied overpotential previously obtained by Vayenas et al. [Catal. Today 11 (1992) 303] and it was necessary to use the more general relationship that applied overpotential is equal to the change in extraction potential plus the change in outer potential. (C) 1998 Elsevier Science B.V. All rights reserved.