Highly dispersed nanometer-sized alpha-Fe2O3 (hematite) and gamma-Fe2O3 (maghemite) iron oxide particles were synthesized by the combustion method. Ferric nitrate was used as a precursor. X-ray diffractometer study revealed the phase purity of alpha- and gamma-Fe2O3. Both the products were characterized using field emission scanning electron microscope and transmission electron microscope for particle size and morphology. Necked structure particle morphology was observed for the first time in both the iron oxides. The particle size was observed in the range of 25-55 nm. Photodecomposition of H2S for hydrogen generation was performed using alpha- and gamma-Fe2O3. Good photocatalytic activity was obtained using alpha- and gamma-Fe2O3 as photocatalysts under visible light irradiation.