Visualizing the Gas Diffusion Induced Ignition of a Catalytic Reaction

Many surface science experiments within heterogeneous catalysis are now conducted in realistic conditions at higher pressures. At these pressures, localized gas conditions will form throughout the reactor. Understanding these gas conditions and their interaction with the catalyst surface at relevant time scales and with spatial resolution is important. To address this issue, we use a combination of techniques that can resolve the gas and surface composition with enough temporal and spatial resolution to show even very rapid gas-surface interactions. Planar laser-induced fluorescence is used to monitor the gas phase, thermography visualizes the surface temperature, and 2D-surface optical reflectance measurements show oxide growth. By combining these techniques in an operando experiment, we demonstrate that the spatial evolution of the catalytic ignition of CO oxidation over Pd(100) at higher pressures is driven by localized gas conditions, emphasizing the need for 2D gas-phase measurements when studying model catalysts in high-pressure conditions.