A facile synthesis method for fabrication of LaFeO3/g-C3N4 nanocomposite as efficient visible-light-driven photocatalyst for photodegradation of RhB and 4-CP

The objective of this paper was to prepare, characterize and evaluate the degradation efficiency of organic pollutants on a perovskite-type LaFeO3-coupled graphitic carbon nitride (g-C3N4) photocatalyst under visible light irradiation. The photocatalyst was synthesized by a simple calcination method. The physical and photophysical properties of the LaFeO3/g-C3N4 composite photocatalyst with various weight ratios of LaFeO3 were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), N-2 adsorption-desorption isotherm measurement, UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and electrochemical measurements. According to the flat band potential estimated by the Mott-Schottky plot and the optical band gap measurements, both semiconductors (LaFeO3 and g-C3N4) can absorb visible light and have band edge positions that allow the transfer of photoelectrons from g-C3N4 to LaFeO3. As compared to g-C3N4, the C 1s and N 1s peaks of the LaFeO3/g-C3N4 composite showed an obvious shift to lower binding energy, implying the existence of a synergistic effect between g-C3N4 and LaFeO3. Furthermore, photocurrent measurement and electrochemical impedance spectroscopy revealed the higher photo-induced charge carrier separation efficiency of the LaFeO3/g-C3N4 composite. The results show that the visible light activity of the composite photocatalyst LaFeO3/g-C3N4 for the degradation of Rhodamine B (RhB) and 4-chlorophenol (4-CP) is higher than that of pure LaFeO3 and g-C3N4, respectively. However, the main reason for the enhanced activity was attributed to the interfacial transfer of photogenerated electrons and holes between LaFeO3 and g-C3N4, leading to the effective charge separation in the composite, inhibited recombination of electron-hole pairs and, finally, enhanced photocatalytic performance of the composite. It was found that the holes, hydroxyl radicals ((OH)-O-center dot) and superoxide radical ions (O-2(-)) are the main reactive species in the degradation reaction of RhB and 4-CP over the LaFeO3/g-C3N4 composite photocatalyst. More importantly, on the basis of the estimated conduction band (CB) from the Mott-Schottky plots, LaFeO3 and the composite show no activity toward hydrogen production under visible light. This work can be applied for the production of other visible-light-responsive photocatalysts based on g-C3N4 that have potential in environmental purification applications.