Fabrication of g-C3N4/TiO2 composite photocatalyst with extended absorption wavelength range and enhanced photocatalytic performance

• The g-C3N4/TiO2 composite photocatalyst has been successfully fabricated by an acetic acid assisted sol–gel method combined with calcination process.
• The aggregation degree of TiO2 nanoparticles could be effectively alleviated due to the introduction of g-C3N4.
• The optical absorption edge of g-C3N4/TiO2 composite has an obvious red shift and the absorption wavelength range is extended after coupling TiO2 with g-C3N4.
• The photocatalytic performance is enhanced due to the formation of heterojunction.

Not only for utilizing both ultraviolet (UV) and visible light but also for enhancing photoinduced carriers separation capability, a composite photocatalyst composed of graphite-like carbon nitride (g-C3N4) and TiO2 has been successfully prepared by an acetic acid assisted sol–gel method combined with calcination process. The as-prepared g-C3N4/TiO2 composite photocatalyst was characterized by using XRD, SEM, TEM, XPS, FT-IR spectra, UV-DRS and TGA. Combined XRD results with SEM images, it indicated that the obtained anatase TiO2 nanoparticles dispersed well on the surface of g-C3N4 sheets and the aggregation degree of TiO2 nanoparticles could be effectively alleviated due to the introduction of g-C3N4. The results of UV-DRS further displayed that the optical absorption edge of g-C3N4/TiO2 composites had an obvious red shift to the longer wavelength in comparison with pure TiO2. Profiting from the above-mentioned advantages, g-C3N4/TiO2 composite showed excellent photocatalytic performance. Under visible light irradiation, all g-C3N4/TiO2 composite samples had more excellent photodegradation performance than pure g-C3N4 or TiO2, and the pseudo-first-order kinetic constant of methyl orange (MO) degradation on optimal g-C3N4/TiO2 composite was 2.80 times as great as that on pure g-C3N4. The photodegradation performance of optimal g-C3N4/TiO2 composite was also investigated under UV–vis light irradiation. Compared with the pure phase (TiO2 or g-C3N4), the composite photocatalytic capability was remarkably enhanced by coupling TiO2 with g-C3N4, which mainly benefited from the effective separation of photoinduced electron–hole pairs and the extended optical absorption range, both owing to the heterojunction built-in between g-C3N4 and TiO2.