2017 Volume 57 Issue 9 Pages 1609-1616
Copper oxide (Cu-oxide) electrodes were produced by the vacuum deposition of pure copper on a stainless steel substrate, followed by oxidation in air between 150 and 550°C. The potentials and durability of the Cu-oxide electrodes under xenon light irradiation were evaluated, and the effects of the microstructure on the electrode performance were discussed. The photocatalytic effect of a p-type semiconductor in a Cu-oxide electrode was confirmed for all treatment temperatures. Electrodes oxidized at 150°C showed a very weak photocatalytic effect because the main phase of the thin film comprised amorphous Cu. The potentials of the electrodes oxidized at 450 and 550°C shifted to more than 230 mV (SCE) after light irradiation but they immediately decreased to 100 mV (SCE) due to the self-corrosion (photo-corrosion) of CuO. The electrodes oxidized at 250 and 350°C retained their photocatalytic activities at irradiation time of more than 24 h. The initial potentials of the electrodes oxidized at 250 and 350°C are 100 mV (SCE) and 280 mV (SCE), respectively. The potential of the electrode oxidized at 250°C increased with time because Cu2O, which was the initial main phase of the electrode, was oxidized to CuO by a surface reaction during irradiation. In the electrode oxidized at 350°C, the photo-excited electrons and the photo-generated holes hardly reacted with the electrode surface by the interactions between the Cu-oxide film and the passive film of stainless steel substrate. The electrode exhibited the best performance in terms of potential and durability during the light irradiation.
