Photo-electrochemical and physical characterizations of a new single crystal POM-based material. Application in photocatalysis

• A new single crystal POM-based hybrid compound was synthesized by hydrothermal route.
• [(H2pip)3][α-PW12O40]2·4H2O exhibits n-type conduction and two optical transitions.
• The valence and conduction bands are made from O2−:2p; W6+:5d orbitals respectively.
• The energy band positions of the compound lead to dye photo-degradation.

A new inorganic-organic hybrid material [(H2pip)3][α-PW12O40]2·4H2O, prepared by hydrothermal method, was structurally characterized by single-crystal X-ray diffraction. The compound based on a Keggin-type polyoxotungstate and piperazine (pip) displays a hybrid framework built from two (α-Keggin)3− polyoxoanions and three (H2pip)2+ hydrogen-bonded fragments, forming 3-D supramolecular architecture. The diffuse reflectance spectrum shows two optical transitions directly (3.27 eV) and indirectly (3.12 eV) allowed. The electrical conductivity follows an exponential law, indicating a semiconducting comportment with activation energy of 14 meV. The Mott-Schottky characteristic, plotted in Na2SO4 (0.5 M) solution indicates n-type conduction with a flat band potential of −0.084 VSCE and electrons density of 4.24 × 1018 cm−3. As application, the photo-degradation of methylene blue (MB) upon UV irradiation was successfully achieved by OH
• radicals. The improved activity is attributed to the potentials closeness of the valence and conduction bands with the radical levels.

Photocatalytic degradation of methylene blue on [(H2pip)3][α-PW12O40]2·4H2O supramolecular material.Figure optionsDownload as PowerPoint slide