Mapping the local reaction kinetics by PEEM: CO oxidation on individual (100)-type grains of Pt foil

► 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.