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<p>The physical and electrochemical properties of the solid solution NiFe<sub>2 − x</sub>Mn<sub>x</sub>O<sub>4</sub> (x = 0; 0.4; 0.8; 1.2; 1.6; 2) synthesized by sol gel route were studied for the first time. The spinels are formed above 400&#xa0;°C, according to the thermal analysis. The spectrophotometry indicates optical transitions (1.00–1.56&#xa0;eV) assigned to (t<sub>2g</sub> - e<sub>g</sub>), directly permitted. The evolution of the conductivity with temperature is characteristic of a conduction mechanism by low polaron hopping (LPH): σ = σ<sub>o</sub>exp{-E<sub>a</sub>/kT}, with activation energy E<sub>a</sub> (0.12–0.33&#xa0;eV). The electrochemical study was undertaken in Na<sub>2</sub>SO<sub>4</sub> (0.1&#xa0;M) solution. Cyclic voltammetry upon visible light indicate <Emphasis Type="BoldItalic">p</Emphasis>-type comportment, corroborated by the chrono-amperometric profiles and capacitance– potential (C<sup>− 2</sup>– E) plots due to metal insertion in octahedral cavities with flat band potentials in the range (-0.04– -0.29 V<sub>SCE</sub>). The electrochemical stability against photo-dissolution is evidenced from the semi-logarithmic plots. Electrochemical impedance spectroscopy (EIS) allows data modeling and an equivalent electric circuit is proposed. The conduction bands of NiFe<sub>2 − x</sub>Mn<sub>x</sub>O<sub>4</sub> are mainly derived from <Emphasis Type="BoldItalic">3d</Emphasis> orbitals, which are independent of pH and can therefore be appropriately localized with respect to redox levels in solution. As application, the electrons in the conduction band (CB ~ -1.8 V<sub>SCE</sub>) permit the degradation of Eosin (15 mg L<sup>− 1</sup>) under visible light. The color removal is followed by UV-Visible spectrophotometry and obeys first-order oxidation kinetics with an abatement of 85% within 6&#xa0;h on NiFe<sub>0.8</sub>Mn<sub>1.2</sub>O<sub>4</sub>.</p>

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Photo-Electrochemical and Physical Properties of the Spinels NiFe2-xMnxO4 for Eosin Photo-Oxidation

  • 期刊论文

  • 发表日期：

    2025年5月16日

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  • G. Rekhila,
  • Z. Boukhemikhem,
  • H. Lahmar,
  • M. Benamira,
  • M. Trari

摘要

The physical and electrochemical properties of the solid solution NiFe2 − xMnxO4 (x = 0; 0.4; 0.8; 1.2; 1.6; 2) synthesized by sol gel route were studied for the first time. The spinels are formed above 400 °C, according to the thermal analysis. The spectrophotometry indicates optical transitions (1.00–1.56 eV) assigned to (t2g - eg), directly permitted. The evolution of the conductivity with temperature is characteristic of a conduction mechanism by low polaron hopping (LPH): σ = σoexp{-Ea/kT}, with activation energy Ea (0.12–0.33 eV). The electrochemical study was undertaken in Na2SO4 (0.1 M) solution. Cyclic voltammetry upon visible light indicate p-type comportment, corroborated by the chrono-amperometric profiles and capacitance– potential (C− 2– E) plots due to metal insertion in octahedral cavities with flat band potentials in the range (-0.04– -0.29 VSCE). The electrochemical stability against photo-dissolution is evidenced from the semi-logarithmic plots. Electrochemical impedance spectroscopy (EIS) allows data modeling and an equivalent electric circuit is proposed. The conduction bands of NiFe2 − xMnxO4 are mainly derived from 3d orbitals, which are independent of pH and can therefore be appropriately localized with respect to redox levels in solution. As application, the electrons in the conduction band (CB ~ -1.8 VSCE) permit the degradation of Eosin (15 mg L− 1) under visible light. The color removal is followed by UV-Visible spectrophotometry and obeys first-order oxidation kinetics with an abatement of 85% within 6 h on NiFe0.8Mn1.2O4.