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<p>Nickel cobaltite (NiCo<sub>2</sub>O<sub>4</sub>) was synthesized via a simple co-precipitation method followed by calcination at 900&#xa0;°C to investigate the relationship between its optical, dielectric, and photocatalytic properties. XRD and Raman analyses confirmed the formation of single-phase cubic spinel NiCo<sub>2</sub>O<sub>4</sub>, while SEM/EDX revealed dense agglomerated particles with homogeneous elemental distribution. UV-Vis diffuse reflectance spectroscopy showed a direct optical bandgap of 1.87 ± 0.03&#xa0;eV, indicating visible-light activation capability. Optical constants and dielectric parameters obtained from spectroscopic ellipsometry revealed a highly polarizable lattice with low optical losses. Impedance spectroscopy demonstrated the presence of conducting grains separated by resistive grain boundaries, suggesting Maxwell–Wagner interfacial polarization and charge-transport limitations. The photocatalytic activity was evaluated through the degradation of rhodamine B under visible-light irradiation, where NiCo<sub>2</sub>O<sub>4</sub> achieved 31.54% discoloration after 90&#xa0;min following pseudo-first-order kinetics. Radical-scavenger experiments indicated that photogenerated holes are the dominant reactive species. The results demonstrate that photocatalytic performance is primarily limited by interfacial charge recombination rather than light absorption, establishing a direct correlation between dielectric behavior and photocatalytic response in NiCo<sub>2</sub>O<sub>4</sub>.</p>

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Linking optical–dielectric response and photocatalytic activity: a correlative study of spinel NiCo2O4 for visible-light degradation of rhodamine B

  • 期刊论文

  • 发表日期：

    2026年8月1日

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

摘要

Nickel cobaltite (NiCo2O4) was synthesized via a simple co-precipitation method followed by calcination at 900 °C to investigate the relationship between its optical, dielectric, and photocatalytic properties. XRD and Raman analyses confirmed the formation of single-phase cubic spinel NiCo2O4, while SEM/EDX revealed dense agglomerated particles with homogeneous elemental distribution. UV-Vis diffuse reflectance spectroscopy showed a direct optical bandgap of 1.87 ± 0.03 eV, indicating visible-light activation capability. Optical constants and dielectric parameters obtained from spectroscopic ellipsometry revealed a highly polarizable lattice with low optical losses. Impedance spectroscopy demonstrated the presence of conducting grains separated by resistive grain boundaries, suggesting Maxwell–Wagner interfacial polarization and charge-transport limitations. The photocatalytic activity was evaluated through the degradation of rhodamine B under visible-light irradiation, where NiCo2O4 achieved 31.54% discoloration after 90 min following pseudo-first-order kinetics. Radical-scavenger experiments indicated that photogenerated holes are the dominant reactive species. The results demonstrate that photocatalytic performance is primarily limited by interfacial charge recombination rather than light absorption, establishing a direct correlation between dielectric behavior and photocatalytic response in NiCo2O4.