Synthesis and characterization of the spinel ZnFe2O4, application to the chromate reduction under visible light

Rekhila, G.; Bessekhouad, Y.; Trari, M.

Synthesis and characterization of the spinel ZnFe2O4, application to the chromate reduction under visible light

2016

Rekhila, G. | Bessekhouad, Y. | Trari, M.

The spinel ZnFe2O4 prepared from nitrate precursors is used for the reduction of chromate under visible light using TiO2 as mediator. A gap of 1.97 eV is obtained for ZnFe2O4 from the diffuse reflectance and the crystallite size (70–130 nm) is determined from TEM measurement. The current–potential characteristic indicates a good electrochemical stability. The photo electrochemical properties permit the construction of the energy diagram of the hetero-system ZnFe2O4/TiO2/HCrO4⁻ solution. The conduction band of the spinel (−1.47 VSCE) favors the physical separation of the electron/hole pairs and the electrons injection into TiO2. The best composition ZnFe2O4 (75%)/TiO2 (25%) is used to catalyze the reaction (2 HCrO4⁻+ 3 C2H4O4+ 1.5 O2+ 8 H⁺→ 2 Cr³⁺+ 6 CO2+ 11 H2O). 60% of Cr(VI) are reduced after 3 h of visible light irradiation and the activity obeys a first order kinetic with a half-life of 70 min. The photocurrent–photovoltage characteristic of the spinel gives an optical-to-electrical energy efficiency of 0.28% and a fill factor of 0.49.

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