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<p>In this work, MnAl<sub>2</sub>O<sub>4</sub> spinel is introduced for the first time as an efficient visible-light photocatalyst for the degradation of Rhodamine B (RhB). The material was synthesized by a controlled co-precipitation route and extensively examined to unveil its structural, optical, dielectric, and electronic characteristics. MnAl<sub>2</sub>O<sub>4</sub> exhibits a direct optical band gap of 2.05&#xa0;eV and weak photoluminescence intensity, indicating suppressed electron–hole recombination and enhanced charge-carrier separation. The refractive index, extinction coefficient, dielectric permittivity, relaxation time, and conductivity profiles reveal strong light–matter interaction, defect-mediated transitions, and favorable dielectric stability, all of which contribute to efficient visible-light activation. XPS valence band analysis places the valence band maximum at 1.87&#xa0;eV, allowing determination of the conduction band minimum at −&#xa0;0.18&#xa0;eV, confirming the material’s ability to generate both ⋅O<sub>2</sub>⁻ and ⋅OH radicals under illumination. Photocatalytic experiments demonstrate that MnAl<sub>2</sub>O<sub>4</sub> achieves 58.5% degradation of RhB within 90&#xa0;min, far outperforming photolysis alone. The reaction follows pseudo-first-order kinetics and the catalyst maintains 42% activity after six cycles, indicating good durability. A mechanistic pathway is proposed based on the experimentally determined band structure and dielectric response. These findings establish MnAl<sub>2</sub>O<sub>4</sub> as a promising, previously unexplored photocatalyst and provide new insights into the role of spinel aluminates in visible-light-driven environmental remediation.</p>

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MnAl2O4 spinel as a new photocatalyst for Rhodamine B removal: linking band structure, optical response, and dielectric dynamics

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Khaled Derkaoui,
  • Ismail Bencherifa,
  • Amal Elfiad,
  • Khadidja Boukhouidem,
  • Mohamed Kechouane,
  • Yamina Mebdoua,
  • Toufik Hadjersi

摘要

In this work, MnAl2O4 spinel is introduced for the first time as an efficient visible-light photocatalyst for the degradation of Rhodamine B (RhB). The material was synthesized by a controlled co-precipitation route and extensively examined to unveil its structural, optical, dielectric, and electronic characteristics. MnAl2O4 exhibits a direct optical band gap of 2.05 eV and weak photoluminescence intensity, indicating suppressed electron–hole recombination and enhanced charge-carrier separation. The refractive index, extinction coefficient, dielectric permittivity, relaxation time, and conductivity profiles reveal strong light–matter interaction, defect-mediated transitions, and favorable dielectric stability, all of which contribute to efficient visible-light activation. XPS valence band analysis places the valence band maximum at 1.87 eV, allowing determination of the conduction band minimum at − 0.18 eV, confirming the material’s ability to generate both ⋅O2⁻ and ⋅OH radicals under illumination. Photocatalytic experiments demonstrate that MnAl2O4 achieves 58.5% degradation of RhB within 90 min, far outperforming photolysis alone. The reaction follows pseudo-first-order kinetics and the catalyst maintains 42% activity after six cycles, indicating good durability. A mechanistic pathway is proposed based on the experimentally determined band structure and dielectric response. These findings establish MnAl2O4 as a promising, previously unexplored photocatalyst and provide new insights into the role of spinel aluminates in visible-light-driven environmental remediation.