Effect of heat-treatment of the oxidizability of smooth platinum anodes

The effect of heat-treatment on the electrochemical oxidizability of a smooth platinum electrode that had previously been oxidized and then reduced was investigated.

The growth rate of the multilayer oxide film by the anodic oxidation at 2·18 V(nhe) decreased with increase of the pre-annealing temperature and time. On the well-annealed electrode surface, only a monolayer oxide film was formed and the multilayer oxide was not developed.

The variation of the oxidizability by the heat-treatment was interpreted in term of the change in surface structure of the electrode. By the oxidation and reduction pre-treatment, the superficial platinum layer may be disordered. The activation energy for the rearrangement of platinum atoms in the disordered layer to the stable lattice position was estimated to be 11 ± 1 kcal/mol on the assumption that the oxidizability is proportional to the coverage of the disordered atoms. This result is in harmony with values calculated on the basis of both the vacancy migration mechanism and the adatom migration mechanism.