Enhancement of photocatalytic degradation of MB by recyclable Li/Mn3O4 thin films

Thin films of physical mixture of Hausmannite Mn3O4 and lithium (Li) are synthesized by spray pyrolysis technique. Structural, morphological, optical, electrical, wettability, and photocatalytic properties have been investigated. X-ray diffraction (XRD) and Raman spectra, Scanning electron microscope (SEM) images, and electrical measurements show that Li nanoparticles are formed both on top surface of the film and inside grain boundaries. Bandgap and Urbach energies and optical relaxation time have been determined from transmittance T and reflectance R spectra. Impedance spectroscopy shows that charge separation increases with Li content, which improves photocatalytic efficiency of the film. The best photocatalytic efficiency is obtained for Li/Mn ratio of 15%. Indeed, the degradation of methylene blue (MB) under ultraviolet (UV) and visible light exposure, is improved by a factor of 5.7 and 2.4, respectively, when compared to undoped Mn3O4. In addition, this film exhibits a high photostability (10 cycles consecutively) under solar light. On the other hand, hydrophobicity reveals the hydrophilic character of the films.