Abstract
Hematite (α-Fe2O3)/graphitic carbon nitride (g-C3N4) nanofilm catalysts were synthesized on fluorine-doped tin oxide glass by hydrothermal and chemical vapor deposition. Scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses of the synthesized catalyst showed that the nanoparticles of g-C3N4 were successfully deposited on α-Fe2O3 nanofilm. The methylene blue degradation efficiency of the α-Fe2O3/g-C3N4 composite catalyst was 2.6 times greater than that of the α-Fe2O3 single catalyst under ultraviolet (UV) irradiation. The methylene blue degradation rate by the α-Fe2O3/g-C3N4 catalyst increased by 6.5 times after 1 mM of hydrogen peroxide (H2O2) was added. The photo-Fenton reaction of the catalyst, UV, and H2O2 greatly increased the methylene blue degradation. The results from the scavenger experiment indicated that the main reactants in the methylene blue decomposition reaction are superoxide radicals photocatalytically generated by g-C3N4 and hydroxyl radicals generated by the photo-Fenton reaction. The α-Fe2O3/g-C3N4 nanofilm showed excellent reaction rate constants at pH 3 (Ka = 6.13 × 10−2 min−1), and still better efficiency at pH 7 (Ka = 3.67 × 10−2 min−1), compared to other methylene blue degradation catalysts. As an immobilized photo-Fenton catalyst without iron sludge formation, nanostructured α-Fe2O3/g-C3N4 are advantageous for process design compared to particle-type catalysts.
Highlights
Advanced oxidation processes (AOPs) include various methods of decomposing organics through the generation of reactive oxygen species (ROS), such as hydroxyl radicals (OH) or superoxide radicals (O2−) [1], which are intermediate reactants with strong oxidizing power
Nano-structured α-Fe2O3 was successfully synthesized on fluorine-doped tin oxide (FTO) glass
Nanoparticles of g-C3N4 were successfully deposited on the synthesized α-Fe2O3 films
Summary
Advanced oxidation processes (AOPs) include various methods of decomposing organics through the generation of reactive oxygen species (ROS), such as hydroxyl radicals (OH) or superoxide radicals (O2−) [1], which are intermediate reactants with strong oxidizing power. The energy levels in the valence and conduction bands where holes and electrons are present are important factors in photocatalytic activity They determine the oxidizable organics and the ROS that can be produced depending on the redox potential. Another important factor in the development of photocatalytic processes is the bandgap energy, which is the difference between energy levels of the valence and conduction bands. Existing hematite-based photocatalysts exhibit high hole–electron recombination due to the narrow bandgap and limited ROS production This is because of the low redox potential of the conduction band; as a result, it is not practical to apply to water treatment. A junction with g-C3N4 enables the use of more ROS species while improving the photoelectrochemical properties of the catalyst
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