Surface Topography and Steps

Surface Topography and Steps.— Over the past ten years a multitude of new techniques has been developed to permit characterisation of catalyst surfaces on the atomic scale so says Somorjai in his excellent review. The essence of his views are worth repeating for he makes abundantly clear the philosophy of his approach. 

The opening sentence needs qualification, for XPS, LEED, and AES give information averaged over many atomic distances. Nor are the substances examined usually catalysts. They are generally single crystals of metals, studied quite properly in their own right as surface systems. Whether or not the results, attitudes of mind, and models which emerge are of importance to catalysis requires proof. 

It is therefore necessary to begin with the warning that one may not be looking at catalysis. Somorjai s approach to catalysis is to adopt the strategy of examining the building blocks and then to assemble them into a model for catalysis. The steps are made up of the study of (/) crystal surfaces and structures plus adsorbed gas, (/7) surface reactions at pressures 10 torr, Hi) reactions at 10 —10 torr, and (zt ) dispersed catalysts. 

The crystals used are spark-cut, polished, etched, annealed, Ar -ion bombarded, and flashed to 1500 K to remove O2, etc. Cutting can be arranged to vary terrace widths and the number of kinks in the steps. Single crystals of area 

Many high Miller index planes for Pt are stable  

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