PHOTOGENERATION OF HYDROGEN USING VISIBLE-LIGHT WITH UNDOPED DOPED ALPHA-FE2O3 IN THE PRESENCE OF METHYL VIOLOGEN

The visible light-induced hydrogen production by water splitting react ions was studied by using undoped or Rh(III)/Cu(II)-doped, with or wit hout RuO2 loaded alpha-Fe2O3 at different pH values in the presence of methyl viologen (MV2+) as an electron relay. Loading with Rh(III) and Cu(II) ions enhances the hydrogen production efficiency of the photoc atalyst. Rh(III) is more efficient than Cu(II) in increasing the photo catalytic activity of alpha-Fe2O3. This increased activity is explaine d on the basis of the role of the metal ions loaded in photogenerated electron-hole separation. Simultaneous loading of RuO2 and Rh(III)/Cu( II) ions further enhances the efficiency. The dark recombination react ion of the evolved hydrogen and oxygen gases has also been investigate d and alpha-Fe2O3 is found to be a good catalyst for both formation (o n illumination) and recombination (in the dark) of the two gases. A re action mechanism involving all these observations has been proposed to explain the photocatalytic cleavage of water.