Heterostructured g-C3N4-TiO2 nanocomposites applied to p-toluic acid degradation under solar light-induced photocatalytic process

Abstract

In this work, heterostructured photocatalysts were prepared with TiO2-P25 nanocrystals dispersed on two-dimensional layers of g-C3N4. Different g-C3N4:TiO2 ratios (25 %, 50 % and 75 %) were prepared using a wet method under ultrasonic exfoliation and thermal treatment under an oxidizing atmosphere. The heterojunctions were confirmed by X-ray diffraction, and electron microscopy, showing TiO2 nanocrystals anchored onto the surface of the g-C3N4 structure. The obtained heterojunctions increased light absorption from the ultraviolet to the visible spectrum and reduced the recombination of photoinduced charge carriers confirmed by photoluminescence and band gap energy (Eg) measurements. The photocatalytic performance was evaluated in the degradation of p-toluic acid (p-TA) (20 mg L–1) under UVA LED at 365 nm, a polychromatic lamp (UVA-UVB-visible) and solar radiation. The g-C3N4:TiO2 ratio of 25 % showed the best performance, reaching 95 % degradation after 180 min under solar radiation. The reuse tests showed that the mineralization capacity determined by total organic carbon (TOC) remained stable for 6 cycles, achieving 80.8 % TOC degradation. The heterojunction induced a significant alteration in the rheological behavior of the suspension, which made the g-C3N4-TiO2 easily recoverable, unlike the pure TiO2. The radical scavengers study indicated that the superoxide anion radical (O2•–) is the main oxidative species in p-TA photodegradation on g-C3N4-TiO2 photocatalyst. The greatest advantage of the g-C3N4 in the composite was the absorption of light in the visible range and facile catalyst recovery for reuse while presenting photocatalytic activity similar to TiO2.