Large Au islands were deposited on TiO2 single crystal electrodes by sputtering, photoredn. and electrodeposition. The photoelectrochem. behavior of Au coated semiconductor electrodes and pure Au electrodes was measured in H2SO4 and in an acid solution containing Fe3+/Fe2+. As the result of anal. of these polarization curves it was found that the contact between Au particles and the semiconductor surface is mainly ohmic in nature. The catalytic behavior of Au islands on the competitive photooxidn. of Ce3+ and H2O were studied by using rotating ring disk electrode with interchangeable disk. Au particles in the form of large islands could only catalyze dark (electrochem.) reactions, but not photoelectrochem. reactions.

Key words: PHOTOCHEMICAL REACTION, GOLD, PHOTOOXIDATION, SULFURIC ACID, METAL ELECTRODE, TITANIUM OXIDE, SINGLE CRYSTALS, PHOTOELECTROCHEMICAL EFFECT, ELECTRIC POTENTIAL, ELECTROCHEMICAL REACTION