Electrocatalysts Are Not Smooth Plates

There are books on physical electrochemistry, which present electrocatalysis with one of the main influential features left out. I refer to surface heterogeneity. Thus, when a surface is viewed under an electron microscope one can see that the apparently smooth electrode surface is in fact not smooth at all. Because the structure of electrode surfaces is, in fact, very much a part of the interpretation of electrocatalysis, I will give a brief sketch of some of the features of a metal surface that may affect surface reactions. 

There are places where these irregular deformities meet and indeed the meeting place of two steps is a particularly active site on the surface where atoms of reactants may become more strongly adsorbed because the absorbed atoms can become bonded in several directions. 

FIGURE 1.11 The structure of the face of a defect-containing single crystal surface with a face-centered cubic system. The spheres indicate the ions in solution, the cubes the metallic adatoms, and the rest the metal adsorbed ensembles. 

We have seen, then, that even if we stick to a tiny area of a single crystal, there are on each of these irregularities not only different planes but also dislocations and new planes. In a real surface, there is a jumble of differently oriented crystals that justify the term polycrystal. 

Why do I go to some length to exemplify the different types of structure on the surface You see, catalysis occurs by different degrees of bindings of different adsorbed atoms on the surface, weaker here, stronger there. 

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