ELECTROCHEMICAL PROPERTIES OF SILICON-CARBIDE

The electrochemical properties of single-crystalline n- and p-type ele ctrodes of two different modifications of SiC in aqueous solutions wer e investigated in the dark and under illumination. The main emphasis w as laid on investigations of the problem of water splitting in photoel ectrolysis cells. No oxygen was detected at SiC electrodes. Instead an odic oxidation of SiC was found leading to the formation of CO2, CO, a nd silicon oxides. Since the oxide film is very porous, the anodic cor rosion current remained on a high level. In the presence of concentrat ed hydrofluoric acid, a different surface layer was formed, possibly d ue to disproportionation processes and the formation of amorphous SiC. Flatband potentials at different pH values were measured and the char ge-transfer processes with various redox systems were examined. A quan titative analysis was very difficult or even impossible, probably due to the complicated surface chemistry and layer formation.