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Abstract

The dynamics of the microscopic elementary processes underlying heterogeneous catalysis may deviate considerably from the simple concepts originating from Langmuir and still forming the basis for modeling reactions under technical conditions. This is demonstrated by several examples applying scanning tunneling microscopy and including the transient formation of non-thermalized surface species as well as the identification of ´active` sites. Experiments with field ion microscopy demonstrated that less active sites may be triggered by concentration waves propagating from active zones due to nonlinear coupling of reaction and diffusion. Related studies with extended single crystal surfaces revealed a wealth of phenomena of spatio-temporal pattern formation on mesoscopic (i.e. μm scale) which may be affected by structuring the surfaces by applying techniques of microlithography.