Interesting and partly new aspects for future work would, e.g., be the experimental verification of approaches aiming at breaking the scaling relations, using model surfaces with well-defined structural elements . Possible candidates would, e.g., be structures where the adsorption energies of reactants and intermediates does not follow a linear scaling law , but also reaction mechanisms involving different reaction sites in a sequence of elementary reaction steps. Another fundamental problem refers to possible effects imposed by the surrounding adlayer. In the examples described above, the total rate was calculated as a sum of the rates obtained on different, separated and thus independent adsorption sites. Therefore, microkinetic models including also adlayer mediated interactions between different neighboring active sites would be highly interesting. In electrocatalysis, the consideration of the electrolyte on an inhomogeneous electrode surface on an atomistic level would be highly desirable . On the way to a more realistic reaction picture the inclusion of mesoscopic transport effects on inhomogeneous surfaces on the reaction characteristics would be a consequent next step to extend the current idealized understanding of catalytic reactions. In all cases, however, and for others as well, the reproducible generation of structurally well-defined surfaces and the quantitative determination of the different structural elements of interest are a time-consuming pre-condition for mapping out unambiguous structure-reactivity correlations.