Photoanodic properties of sol-gel-derived Fe2O3 thin films containing dispersed gold and silver particles

alpha-Fe2O3 films containing dispersed Au and Ag particles 5-20 nm in size were prepared on nesa silica glass substrates by the sol-gel method, using solutions of a mole ratio Fe(NO3)(3).9H(2)O: (HAuCl4.4H2O or AgNO3): CH3COCH2COCH3:CH3OCH2CH2OH = 1:0.06:2:20 as the coating solution. The anodic photocurrent-potential characteristics and the action spectra were investigated in a three-electrode cell employing the film electrode as the working electrode. When the film electrode was illuminated with intense white light, the embedded metal particles did not affect the photoanodic properties of the electrode significantly. When the film electrode was illuminated with weak white light or weak monochromatic light, the metal particles, especially Au particles, enhanced the anodic photocurrent; the Au particles embedded in the electrode enhanced the quantum efficiency, IPCE, by about 8 times at a wavelength of 400 nm. Deposition of An particles just on the surface of the Fe2O3 film also increased the photoanodic current, suggesting that the enhanced photocurrent is provided by the An particles on the electrode surface, which are supposed to catalytically promote the transfer of the hole in the conduction band of Fe2O3 to the electrolyte.