The nature of oxidized platinum electrodes

It has been known for many years [44, 45] that Pt electrodes subjected to a positive potential form some kind of oxide film which is limited to about one or two monolayers before oxygen evolution occurs. This can be seen clearly in the voltammogram of a Pt electrode in acid solution (see Fig. 10). When the solution and the electrode surface are clean, the charge for the adsorption of this film is exactly equal to that for its desorption, but this charge cannot be ascribed unambiguously to the formation and removal of particular chemical species, using electrochemical measurements alone. An excellent summary of the problems is given by Woods [46]. 

The first attempt to use ex-situ measurements of the oxidation state of Pt and O in these thin films was made by Kim et al. [3] who used XPS. They were able to study oxide films from the beginning of oxidation about +1.0V (RHE) up to + 2.5 V using simple insertion into the UHV system after washing the electrode. They interpreted their results in terms of three Pt 

This type of information has, so far, eluded those using purely electro- 

---