Investigation of gas-phase coupling in the CO oxidation reaction on polycrystalline Pt

Introduction The oxidation of CO on Pt catalysts has been shown to exhibit complex, non-linear behavior, such as reaction rate oscillations and spatio-temporal pattern formation over a wide range of reaction conditions [1]. At pressures above 1x10 Torr, individual regions of the catalyst surface are primarily coupled through thermal fluctuations within the catalyst itself or by variations in reactant pressure in the gas phase above the surface. At lower pressures, where the system is isothermal, coupling through the gas-phase [2] and by surface diffusion of adsorbates results in spatial synchronization. For the gas-phase coupling mode in particular, little is known about the spatial limits in which different surface regions may communicate through the gas phase. This is primarily due to experimental difficulties associated with locating and imaging dynamic behavior on the surface while simultaneously detecting local changes in the gas phase above the surface. In this study, we employ real time surface imaging combined with scanning mass spectrometry to analyze the gas phase above a polycrystalline Pt foil during CO oxidation to investigate gas-phase coupling behavior.