Photocatalytic H₂ generation from spinels ZnFe₂O₄, ZnFeGaO₄ and ZnGa₂O₄

The three spinels ZnFe2O4, ZnFeGaO4 and ZnGa2O4 were synthesised by conventional solid state reaction method. ZnFeGaO4 has unit cell parameter between the parent spinels and shows appreciable absorption in visible light range with a band gap similar to 1.9 eV. Photocatalytic experiments show that ZnFeGaO4 has a reasonable hydrogen production rate (similar to 9 mu mol h(-1)/g catalyst) under visible light irradiation (lambda >= 420 nm) but exhibits an improved performance ( hydrogen production rate similar to 971 mu mol h(-1)/g catalyst) compared with parent ZnFe2O4 compound (hydrogen production rate similar to 861 mu mol h(-1)/g catalyst) under full range irradiation (lambda >= 250 nm). The photo-electrodes prepared by electrophoretic deposition of spinel powders onto the fluorine doped tin oxide glass showed a clear impedance response under irradiation. Introducing Ga into the ZnFe2O4 structure seems to enhance the light absorbance in the UV region and modify the electronic structure which accounts for the improved photocatalytic activity. (c) 2012 Elsevier B.V. All rights reserved.