Correlation between surface properties and photocatalytic and photoelectrochemical activity of In2O3 nanocrystalline films and powders

Nanocrystalline In2O3 thin films and powders have been prepared by sol–gel procedure and characterized by various bulk and surface techniques (X-ray diffraction, X-ray photoelectron spectroscopy and photoelectrochemical spectroscopy). Photocatalytic reactivity for rhodamine 6G photodestruction and photoelectrochemical (PEC) properties have been studied for the In2O3 samples heated at different temperatures. The photocatalytic activity of the powder grows initially with increasing annealing temperature from 200 to 300°C and then drops sharply with further increase in temperature. A strikingly large difference in photocurrent onset potentials and photocurrent quantum yields has been revealed for the films heated at 200 and 400°C. The susceptibility of the oxide surface to hydroxylation appears to be a key factor responsible for the sharp change in photoreactivity and PEC properties.