Physical and Photo-electrochemical Characterization of Hybrid Material Synthetized by Hydrothermal Route for Photo-Degradation of Methyl Violet Dye

The hybrid material AlCo2P3O4·1/2H2O: DIMPPZ (AlCoP-DIMPPZ; 1, 4-Dimethyl piperazine: DIMPPZ) was synthesized hydrothermally at 453 K and characterized by X-ray diffraction (XRD), FT-IR and diffuse reflectance spectroscopies, SEM / EDX analysis. The crystal symmetry is rhombohedral and the XRD pattern is consistent with a single phase (S.G. R3-)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R\stackrel{-}{3})$$\end{document} isotypic to ACP-CHA9 (C4) AlCo2P3O4·1/2H2O with cell parameters in the hexagonal description: a = 13.5494 Å and c = 15.2795 Å. The optical study revealed a direct electronic transition at 1.82 eV, assigned to lift of degeneracy of CoII in a low spin configuration tetrahedrally bonded. The SEM image showed a more or less homogeneous morphology with similar grain sizes ranging from 3.5 to 6 μm whereas the FT-IR spectrum exhibits characteristic peaks of (PO4)3− units and C=C bonds. To our knowledge, no photo-electrochemistry has been reported to date and the low exchange current density (~ 2 mA cm−2) is consistent with the electrochemical stability in Na2SO4 (0.1 M) solution. The dependence of the interfacial capacitance (C−2) on the potential (E) is typical of n-type behaviour with an electron density (ND) of 2.14 × 1018 cm−3 and a flat band potential (Efb) of 0.59 VSCE. The valence band with an energy of 7.10 eV /vacuum (2.35 VSCE) derives from 3d wave function originating from Co2+ ion. The semicircle at high frequencies in the electrochemical spectroscopy with an impedance of 910 Ω cm2 is due to the intrinsic property, which decreases to 750 Ω cm2 under visible light, corroborating the semi conductivity of the material. As application, the hybrid material was tested for the first time for the oxidation of Methyl Violet (MV), with an abatement of 65% under visible light (15 mW cm−2) for 420 min while the adsorption of 33%. Based on the energy diagram, the title compound will be used as O2 photo electrode.