Catalytic CO oxidation has been investigated under low pressure conditions (p B 10~6 mbar) employing porous Pt Ðlms on a solid state electrolyte (yttrium stabilized as catalyst. The samples were ZrO 2 \ YSZ) characterized by impedance spectroscopy and linear sweep voltammetry before rate measurements were conducted in an UHV chamber with a di †erentially pumped mass spectrometer, a Kelvin probe for integral and a photoelectron emission microscope (PEEM) for spatially resolved measurements of the work function (WF). Di †erent types of samples prepared by di †erent groups were investigated. An electrocatalytic e †ect was found for all samples but within the experimental uncertainty (up to a factor of two) the e †ect was Faradaic. Surprisingly, despite nearly identical electrochemical characteristics the electrocatalytic behavior of the catalysts with the porous Pt Ðlms varied drastically depending on the preparation. Whereas on the samples provided from a di †erent group the WF of the porous Pt Ðlms followed more or less the variation in the electric potential the samples prepared here exhibited no detectable WF change at all upon variation of (V WR), Within the spatial resolution of PEEM (*x B 1 lm) the observed WF changes occurred spatially V WR . homogeneous.

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In our Letter we employed reaction-diffusion models of a composite (Pt͞Rh) catalytic medium to interpret experimental data reporting chemical wave initiation at the material interface [1]. Our models, a scalar caricature as well as a mechanistic model of NO reduction, accounted for diffusive coupling between domains catalyzing a nonlinear reaction. The boundary conditions at the interface demanded the continuity of species flux and coverage. It was pointed out by Dr. V. Zhdanov that one of the boundary conditions used in our mechanistic model of NO reduction is incorrect. Instead of continuity of surface coverages one should impose the continuity of chemical potentials [2].We have tested the robustness of the main findings reported in our previous work by analyzing the effects of this change in the boundary condition on bifurcations and dynamics of the single species, two-domain model of NO reduction:NO 1 Z $ NO ads ,

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