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Journal of Materials Science

, Volume 42, Issue 15, pp 6469–6476 | Cite as

The physical and photo electrochemical characterization of the crednerite CuMnO2

  • Yassine Bessekhouad
  • Yamina Gabes
  • Aissa Bouguelia
  • Mohamed Trari
Article

Abstract

CuMnO2 is prepared via Cu+ → Li+ exchange in molten copper (I) chloride. It crystallizes in a monoclinic structure (SG C2/m) where the MnO6 octahedra elongation is ascribed to the Yahn–Teller (Y–T) effect of Mn3+ ions. From chemical analysis, the oxide is more accurately formulated as CuMnO2.01. Above 250 °C, it undergoes a reversible transition to spinel CuxMn3−xO4 and beyond 940 °C it converts back to Cu1.1Mn0.9O2. Extrapolation of high-temperature magnetic data indicates T-intercept θp of −450 K and an effective moment of 5.22 μB, consistent with strong antiferromagnetism in the basal plans and high spin (HS) configuration Mn3+. This value is slightly larger than that of the spin only moment, a behavior ascribed to Cu2+ originating from oxygen insertion. As prepared, CuMnO2 displays p-type conductivity with an activation energy of 0.16 eV. Most holes generated upon band gap excitation are trapped on Cu+ ions and the conduction occurs by small polarons hopping between neighboring sites. The linear increase of thermopower for Cu1.05Mn0.95O2 with temperature indicates a hole mobility μ300 K (3.5 × 10-6 cm2 V−1 s−1) thermally activated. CuMnO2 is made p- and n-type and the difference in the carriers mobilities is attributed to different oxygen polyhedra. The title oxide, characterized photo electrochemically, exhibits a pH-insensitive flat band potential (+0.13 VSCE). The valence band, located at 5.3 eV below vacuum, is made up of Cu 3d orbital. As application, the powder showed a good performance for the H2-photo evolution.

Keywords

Small Polaron MnO6 Octahedra Oxygen Insertion Antiferromagnetic Lattice Zero Zeta Potential 

Notes

Acknowledgements

This work was financially supported by the Faculty of Chemistry (Algiers) under the contact No. E1602/07/04. The authors would like to thank B. Biri for his technical assistance and helpful discussions.

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Yassine Bessekhouad
    • 1
  • Yamina Gabes
    • 1
  • Aissa Bouguelia
    • 1
  • Mohamed Trari
    • 1
  1. 1.Laboratoire de Stockage et de Valorisation des Energies RenouvelablesUSTHBAlgiersAlgeria

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