The locally-resolved reaction kinetics of CO oxidation on individual (100)-type grains of a polycrystalline Pt foil was monitored in situ using photoemission electron microscopy (PEEM). Reaction-induced surface morphology changes were studied by optical differential interference contrast microscopy and atomic force microscopy (AFM). Regions of high catalytic activity, low activity and bistability in a (p,T)-parameter space were determined, allowing to establish a local kinetic phase diagram for CO oxidation on (100) facets of Pt foil. PEEM observations of the reaction front propagation on Pt(100) domains reveal a high degree of propagation anisotropy both for oxygen and CO fronts on the apparently isotropic Pt(100) surface. The anisotropy vanishes for oxygen fronts at temperatures above 465 K, but is maintained for CO fronts at all temperatures studied, i.e. in the range of 417 to 513 K. A change in the front propagation mechanism is proposed to explain the observed effects.
► Kinetics of the CO oxidation on (100)-type grains of a polycrystalline Pt foil was studied in situ. ► Photoemission electron microscopy was used to study the local reaction kinetics on a mm-scale. ► Local kinetic phase diagrams for individual Pt(100) grains were obtained. ► Anisotropy of propagating reaction fronts on the apparently isotropic Pt(100) surface is explained.