M-substituted (M = Co, Ni and Cu) zinc ferrite photo-catalysts for hydrogen production by water photo-reduction

A(0.2)Zn(0.8)Fe(2)O(4) ferrites with A = Co, Ni and Cu were successfully prepared by co-precipitation followed by annealing at 650 degrees C. They were characterized by using XRD, EDX, BET, FTIR, RDS, electrical conductivity, Current-Potential, Mott-Schottky and Nyquist techniques and their photo-catalytic properties were evaluated in hydrogen production through water photo-reduction. XRD revealed the formation of cubic ferrospinel structures with particle sizes in the nano-range. BET surface areas of the ternary spinels were higher than that of the binary ZnFe2O4. The electrical conductivities of A(0.2)Zn(0.8)Fe(2)O(4) were found to obey the Arrhenius law with activation energies of conduction between 0.17 and 0.31 eV. They were found to be n-type semiconductors with narrow band gap. The photo-catalytic results for hydrogen production indicated that the Co substitution dramatically enhances the catalytic activity of ZnFe2O4. This substituted zinc ferrite shows the highest photo catalytic activity under visible light irradiation, which varies as follows: Co0.2Zn0.8Fe2O4 >> Ni0.2Zn0.8Fe2O4 > ZnFe2O4 > Cu0.2Zn0.8Fe2O4. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.