  We assess heat and mass transfer limitations in in situ studies of model
catalysts with a first-principles based multiscale modeling approach that
integrates a detailed description of the surface reaction chemistry and the
macro-scale flow structures. Using the CO oxidation at RuO2(110) as a
prototypical example we demonstrate that factors like a suppressed heat
conduction at the backside of the thin single-crystal, and the build-up of a
product boundary layer above the flat-faced surface play a significant role.
