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 reactions was studied by using undoped or Rh(III)/Cu(II)-doped, with or without 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 photocatalyst. Rh(III) is more efficient than Cu(II) in increasing the photocatalytic activity of alpha-Fe2O3. This increased activity is explained 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 reaction of the evolved hydrogen and oxygen gases has also been investigated and alpha-Fe2O3 is found to be a good catalyst for both formation (on illumination) and recombination (in the dark) of the two gases. A reaction mechanism involving all these observations has been proposed to explain the photocatalytic cleavage of water.