The Photoresponse and Donor Concentration of Plasma Sprayed TiO₂ and TiO₂-ZnO Electrodes

The photoelectrochemical characteristics of plasma sprayed porous TiO₂, TiO₂-5%ZnO and TiO₂-10%ZnO electrodes in 0.1N NaOH solution were studied through a three-electrode cell system. The microstructure, morphology and composition of the electrodes were analyzed using electron probe surface roughness analyzer (ERA-8800FE), scanning electron microscope (SEM) and X-ray diffraction. The results showed that the sprayed electrodes had a porous microstructure, which was affected by the plasma spraying parameters and composition of the powders. TiO₂-ZnO electrodes consisted of anatase TiO₂, rutile TiO₂ and Zn₂Ti₃O₈ phase. The photoresponse characteristics of the plasma sprayed electrodes were comparable to that of single crystal TiO₂, but the breakdown voltage was approximate to 0.5V (vs. SCE). The short-circuit photocurrent density increased with a decrease of donor concentration, which was calculated according to Garner-Bulter model. For the lowest donor concentration of a TiO₂-5%ZnO electrode prepared under the arc current of 600A, the short-circuit photocurrent density was approximately 0.4mA/cm² higher than that of the TiO₂ electrodes under 30mW/cm² xenon light irradiation. The photocurrent density increased linearly with light intensity.