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<p>NiFe<sub>0.4</sub>Mn<sub>1.6</sub>O<sub>4</sub> synthetized by sol–gel route is successfully exploited for the Hydrogen Evolution Reaction (HER) under visible light illumination. The oxide crystallizes in a spinel structure with a crystallite size of 51&#xa0;nm, smaller than that observed by transmission electron microscopy (TEM, 460&#xa0;nm), indicating an agglomeration process. <i>p</i>-type conduction is indicating by the positive thermoelectric power (S<sub>300K</sub> =  + 130&#xa0;µV&#xa0;K<sup>−1</sup>), with an activation energy of 290&#xa0;meV. The direct band gap (E<sub>g</sub> = 1.04&#xa0;eV), comes from the lifting of degeneracy of the <i>3d</i> orbital of (Fe, MnO<sub>6</sub>) octahedra is obtained from the diffuse reflectance, ideal for the exploitation of the solar spectrum. The “<i>Capacitance –Potentiel</i>” characteristic yields a hole concentration (N<sub>A</sub>) of 0.28 × 10<sup>16</sup>&#xa0;cm<sup>−3</sup> and a flat band potential (E<sub>fb</sub>) of −&#xa0;0.04 V<sub><i>SCE</i></sub>. The correlation between physical and electrochemical properties predict the feasibility of NiFe<sub>0.4</sub>Mn<sub>1.6</sub>O<sub>4</sub> for HER from an energy diagram. The conduction band (−&#xa0;0.79 VSCE) is cathodically positioned relative to the H<sub>2</sub>O/H<sub>2</sub> couple (~ −&#xa0;0.46 VSCE), thus allowing HER under visible irradiation. The optimization of NiFe<sub>0.4</sub>Mn<sub>1.6</sub>O<sub>4</sub> dose, pH and S<sub>2</sub>O<sub>3</sub><sup>2−</sup> concentration has been undertaken, giving a maximal H<sub>2</sub> volume of 70&#xa0;µmol and an evolution rate of 7.9&#xa0;µmol&#xa0;g<sup>−1</sup>&#xa0;min<sup>−1</sup>.</p>

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Water reduction on the spinel NiFe0.4Mn1.6O4 upon visible light illumination

  • 期刊论文

  • 发表日期：

    2025年12月5日

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  • M. Trari,
  • G. Rekhila,
  • K. Cherifi

摘要

NiFe0.4Mn1.6O4 synthetized by sol–gel route is successfully exploited for the Hydrogen Evolution Reaction (HER) under visible light illumination. The oxide crystallizes in a spinel structure with a crystallite size of 51 nm, smaller than that observed by transmission electron microscopy (TEM, 460 nm), indicating an agglomeration process. p-type conduction is indicating by the positive thermoelectric power (S300K =  + 130 µV K−1), with an activation energy of 290 meV. The direct band gap (Eg = 1.04 eV), comes from the lifting of degeneracy of the 3d orbital of (Fe, MnO6) octahedra is obtained from the diffuse reflectance, ideal for the exploitation of the solar spectrum. The “Capacitance –Potentiel” characteristic yields a hole concentration (NA) of 0.28 × 1016 cm−3 and a flat band potential (Efb) of − 0.04 VSCE. The correlation between physical and electrochemical properties predict the feasibility of NiFe0.4Mn1.6O4 for HER from an energy diagram. The conduction band (− 0.79 VSCE) is cathodically positioned relative to the H2O/H2 couple (~ − 0.46 VSCE), thus allowing HER under visible irradiation. The optimization of NiFe0.4Mn1.6O4 dose, pH and S2O32− concentration has been undertaken, giving a maximal H2 volume of 70 µmol and an evolution rate of 7.9 µmol g−1 min−1.