Visible light induced hydrogen evolution on new hetero-system ZnFe2O4/SrTiO3

The physical properties and photoelectrochemical characterization of the spinel ZnFe2O4, elaborated by chemical route, have been investigated for the hydrogen production under visible light. The forbidden band is found to be 1.92 eV and the transition is indirectly allowed. The electrical conduction occurs by small polaron hopping with activation energy of 0.20 eV. p-type conductivity is evidenced from positive thermopower and cathodic photocurrent. The flat band potential (0.18 V-SCE) determined from the capacitance measurements is suitably positioned with respect to H2O/H-2 level (-0.85 V-SCE). Hence, ZnFe2O4 is found to be an efficient photocatalyst for hydrogen generation under visible light. The photo-activity increases significantly when the spinel is combined with a wide band gap semiconductor. The best performance with a hydrogen rate evolution of 9.2 cm(3)h(-1) (mg catalyst)(-1) occurs over the new hetero-system ZnFe2O4/SrTiO3 in Na2S2O3 (0.025 M) solution. (C) 2009 Elsevier Ltd. All rights reserved.