Effect of amorphous alumina and α-alumina on optical, color, fluorescence properties and photocatalytic activity of the MnAl2O4 spinel oxides

A series of the alumina decorated MnAl2O4 photocatalysts were synthesized via a gamma-ray irradiation assisted polyacrylamide gel method and were evaluated for the photocatalytic degradation of congo red dye under simulated sunlight irradiation. The structural, infrared spectroscopy, X-ray photoelectron spectroscopy and color performance analysis found that the Al ion incomplete enter the host lattice of MnAl2O4 and the color properties of as-prepared samples strongly dependent on the sintering temperature. The optical, fluorescence and electrochemical characterization reveals that a small amounts of organic impurities and amorphous alumina can helps in increasing light absorption, reducing the Eg value, suppressing electron hole pair recombination and promoting charge transfer and separation. A small amounts of organic impurities and amorphous alumina decorated MnAl2O4 photocatalysts exhibits an excellent photocatalytic activity due to the synergistic effect of light absorption, organic impurity, the phase transition of alumina, Eg value, charge transportation and separation efficiency. The possible photocatalytic mechanism of the alumina decorated MnAl2O4 photocatalyst for degradation of congo red dye have been discussed on the basis of the characterization results.