The surface characteristics of polycrystalline cobalt electrooxidised in sulfuric acid solutions

The oxidation of cobalt electrodes has been carried out by means of cyclic voltammetry and coulometry under controlled potential in sulfuric acid solu tions of different concentrations. The electrochemical scanning tunneling m icroscope/scanning tunneling microscope (ECSTM/STM) systems constructed by the authors and scanning electron microscopy (SEM) with the SEM-EDX system of surface analysis of the elements have been used. The procedure applied i n this work made it possible to observe the fragments of the same surface b y means of SEM and ECSTM/STM. The most typical images for a polycrystalline Co electrode with a +/-10% accuracy at the scales of 4800 nm x 4800 nm and 100 nm x 100 nm are presented and the results are discussed. In a diluted electrolyte (0.1 M), irregular forms of a stable cobalt oxide with Co:O rat io similar to 1:1 appear, Unreproducible results have been obtained in a 1. 0 M H2SO4 solution. Compact and relatively regular layers of cobalt oxide o f the same ratio have been obtained in 0.1 M H2SO4, as well as in 10.0 M su lfuric acid solution, under controlled oxidation potential at the passivati on range.