The preparation and properties of a g-C3N4/AgBr nanocomposite photocatalyst based on protonation pretreatment

A novel method was proposed to fabricate a g-C3N4/AgBr nanocomposite photocatalyst by loading AgBr nanoparticles onto the g-C3N4 matrix, which was protonated under hydrothermal conditions in the presence of sulfuric acid. X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), UV-vis diffuse reflectance spectra (DRS), electrochemical impedance spectroscopy (EIS), electron paramagnetic resonance (EPR), photoluminescence (PL) and reactive species trapping measurement were adopted to analyze the structure and properties of the g-C3N4/AgBr nanocomposite photocatalyst. The photocatalytic activities of the as-prepared samples were also evaluated by decomposing methyl orange (MO) in aqueous solution under visible light illumination. The results show that the protonation pretreatment of a g-C3N4 matrix can not only provide growth sites for AgBr grains, but also increase the porosity of the g-C3N4 matrix. Therefore, the AgBr nanoparticles can be uniformly loaded onto the surface of the g-C3N4 matrix, and the specific surface area of the composite can be increased obviously. As a result, the best photodegradation rate of MO over g-C3N4/AgBr nanocomposite photocatalyst is 33.8 and 2.1 times higher than that over pure g-C3N4 and AgBr samples, respectively. Combining the results of EIS Nyquist plots, EPR spectroscopy, reactive species trapping measurement and (OH)-O-center dot trapping PL spectra, a Z-scheme charge transfer mechanism is proposed.