Abstract
Photoelectrochemical technique was applied to characterize the dispersion state of TiO2 particles in Ni-TiO2 composite films. Ni-TiO2 composite films were prepared by dispersion plating under various conditions, and when they were used as the photoelectrode in sulfuric acid solution, the differences in the dispersion of the TiO2 particles in the films modified the photocurrent-potential curve. The photocurrent obtained showed one peak (A) in the region of less noble potential and an ordinal increase (B) in the noble potential region. The increased exposure of TiO2 particles on the surface as a result of chemical etching caused an increase in photocurrent (B), and the thicker the film grew, the smaller its photocurrent (B) became. This is due to the fact that the TiO2 particles in the film acted as an electrical resistance. When composite films were formed under high plating current density, codeposition of TiO2 particles was suppressed and the corresponding photocurrent (A) was relatively small. The condensation of TiO2 particles in the film reduced the photocurrent park (A), but increased photocurrent (B). This behavior suggests that the first photocurrent peak (A) located in the less noble potential region corresponds to the photoelectrochemical dissolution of the nickel matrix, and that the second increase (B) located in the noble potential region corresponds to the photoelectrochemical oxidation (probably O2 evolution) on the TiO2 particles.
