Synthesis and characterization of αFe2−xMxO3 (M = Co, Ni, Cu or Zn) photocatalysts for the degradation of the indigo carmine dye in water

If suitably prepared, hematite (αFe2O3)-based materials may be effective photocatalysts under visible light. Doping hematite with cations is assumed to improve the chemical photocatalyst performance of hematite. To check for these effects, the catalytic efficiency under visible radiation of the pure, Co-, Ni-, Cu-, or Zn-doped nanosized hematite samples was tested on the degradation of the indigo carmine dye, as a model molecule to simulate a generic organic substrate. These semiconductors with photocatalyst activity were first characterized by powder X-ray diffractometry, Mössbauer spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometer, diffuse reflectance spectroscopy and by energy dispersive X-ray fluorescence. The most efficient photocalysts for the indigo carmine dye degradation were the Cu- and Zn-doped hematite samples. The relatively higher photocatalytic activity of these two samples are interpreted as being due to their relatively higher ability, among the tested semiconductors, to absorb the visible light, efficient charge separation and e−-transference.