Enhanced photodegradation activity of methyl orange over Z-scheme type MoO3-g-C3N4 composite under visible light irradiation

Novel Z-scheme type MoO3-g-C3N4 composites photocatalysts were prepared with a simple mixing-calcination method, and evaluated for their photodegradation activities of methyl orange (MO). The optimized MoO3-g-C3N4 photocatalyst shows a good activity with a kinetic constant of 0.0177 min(-1), 10.4 times higher than that of g-C3N4. Controlling various factors (MoO3-g-C3N4 amount, initial MO concentration, and pH value of MO solution) can lead to the enhancement of the photocatalytic activity of the composite. Only MoO3 and g-C3N4 are detected with X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectra. N-2 adsorption and UV-vis diffuse reflectance spectroscopy (DRS) results suggest that the addition of MoO3 slightly affects the specific surface area and the photoabsorption performance. The transmission electron microscopy (TEM) image of MoO3-g-C3N4 indicates a close contact between MoO3 and g-C3N4, which is beneficial to interparticle electron transfer. The high photocatalytic activity of MoO3-g-C3N4 is mainly attributed to the synergetic effect of MoO3 and g-C3N4 in electron-hole pair separation via the charge migration between the two semiconductors. The charge transfer follows direct Z-scheme mechanism, which is proven by the reactive species trapping experiment and the (OH)-O-center dot-trapping photoluminescence spectra.