Physical and photoelectrochemical properties of the spinel LiMn2O4 and its application in photocatalysis

• Published in: The Journal of physics and chemistry of solids 2018-07, Vol.118, p.62-67
• Main Authors: Douafer, S., Lahmar, H., Benamira, M., Rekhila, G., Trari, M.
• Format: Article
• Language: English
• Subjects: LiMn2O4; Photocatalyst; Sol-gel method; Solar irradiation
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2018.02.053

Nanocrystalline lithium manganese oxide (LiMn2O4), synthesized by the sol-gel method, crystallizes in the spinel structure. The physical, electrical, and photoelectrochemical properties were studied for the photocatalytic degradation of methyl orange, a toxic compound, under solar irradiation. The diffuse reflectance spectrum allowed the direct band gap (1.99 eV) to be calculated. The Fourier transform IR spectrum contained all the characteristic peaks of the spinel LiMn2O4, which exhibited n-type behavior. The thermal evolution of the electrical conductivity exhibited an Arrhenius-type behavior with an activation energy of 0.27 eV. The Mott-Schottky curve allowed the determination of the flat band potential (−0.24 V vs. the saturated calomel electrode) as well as the carrier density (1.78 × 1021 cm−3). The detoxification of water containing methyl orange with LiMn2O4 as a photocatalyst was successfully completed. Total degradation for an initial concentration of 10−4 M methyl orange at pH ∼3 and 25 °C was obtained in less than 5 h under solar irradiation. No adsorption was obtained in the dark in the presence of LiMn2O4. [Display omitted] •The physical, optical, and photoelectrochemical properties of LiMn2O4 prepared by the sol-gel method were studied.•The photocatalytic activity of LiMn2O4 under sunlight was tested for the first time for the degradation of methyl orange.•The energy diagram of LiMn2O4 was established regarding the different characterizations performed.•The photocurrent is characteristic of an n-type semiconductor. The flat band potential was determined from the Mott-Schottky curve.•In less than 2 h and at pH∼ 3, 50% degradation of methyl orange was obtained.