The properties and photocatalytic performance comparison of Fe3+-doped g-C3N4 and Fe2O3/g-C3N4 composite catalysts

Fe3+-doped g-C3N4 and Fe2O3/g-C3N4 composite catalysts were prepared by a simple method using melamine and ferric nitrate as precursors. X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectra, scanning electron microscopy, photoluminescence, X-ray photoelectron spectroscopy and photocurrent measurements were used to characterize the prepared catalysts. The results indicated that Fe3+ was inserted at an interstitial position of g-C3N4 by coordinating to N atoms, which exist in a form completely different from those in the Fe2O3/g-C3N4 composite. The different form of Fe species caused the difference in optical properties, energy band structure and electrons–holes separation rate. The activities of Fe3+-doped g-C3N4 and Fe2O3/g-C3N4 composite catalysts were tested by the photocatalytic degradation of Rhodamine B (RhB) under visible light. The rate constant of Fe3+-doped g-C3N4 was 2.5 and 1.8 times higher than that of the g-C3N4 and Fe2O3/g-C3N4 composite. The possible mechanism is proposed.