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

Abstract

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. N₂ 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-trapping photoluminescence spectra.