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Solid electrolyte aided study of the mechanism of CO oxidation on polycrystalline platinum

Gentekakis Ioannis, Neophytides, S. G, Vayenas, Costas G

Πλήρης Εγγραφή

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Περίληψη

The mechanism of CO oxidation on polycrystalline Pt at atmospheric pressure has been investigated by combining kinetic and simultaneous potentiometric studies in a gradientless reactor containing one or two polycrystalline Pt films supported on stabilized zirconia. The initial oxidation state of the catalyst was found to have an important effect both on the steady-state behavior and on the waveform of rate and emf oscillations. A simple kinetic model where both oxygen adsorption and surface reaction are rate limiting is found to describe semiquantitatively the steady-state kinetic and potentiometric results both on preoxidized and on prereduced surfaces. The oscillatory behavior of the system was studied in detail by simultaneous mass spectroscopic monitoring of the concentrations of O2 and CO2. The kinetic and potentiometric results suggest strongly that the oscillations are caused by periodic formation and consumption of surface PtO2. The formation of PtO2 is verified by a series of surface COO2 titration experiments. The experiments with two polycrystalline films show that oscillation synchronization occurs via the gas phase as the two films exposed to the same gaseous environment exhibit synchronous oscillations in the surface oxygen activity.

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