Hematite/Graphitic Carbon Nitride Nanofilm for Fenton and Photocatalytic Oxidation of Methylene Blue

Hematite (α-Fe 2 O 3 )/graphitic carbon nitride (g-C 3 N 4 ) 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-C 3 N 4 were successfully deposited on α-Fe 2 O 3 nanofilm. The methylene blue degradation efficiency of the α-Fe 2 O 3 /g-C 3 N 4 composite catalyst was 2.6 times greater than that of the α-Fe 2 O 3 single catalyst under ultraviolet (UV) irradiation. The methylene blue degradation rate by the α-Fe 2 O 3 /g-C 3 N 4 catalyst increased by 6.5 times after 1 mM of hydrogen peroxide (H 2 O 2 ) was added. The photo-Fenton reaction of the catalyst, UV, and H 2 O 2 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-C 3 N 4 and hydroxyl radicals generated by the photo-Fenton reaction. The α-Fe 2 O 3 /g-C 3 N 4 nanofilm showed excellent reaction rate constants at pH 3 (K a = 6.13 × 10 −2 min −1 ), and still better efficiency at pH 7 (K a = 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-Fe 2 O 3 /g-C 3 N 4 are advantageous for process design compared to particle-type catalysts.