Silver decorated TiO2/g-C3N4 bifunctional nanocomposites for photocatalytic elimination of water pollutants under UV and artificial solar light

Abstract

Ternary TiO2/g-C3N4@Ag nanocomposites with controlled composition were synthesized and used as highly effective bifunctional photocatalysts. TiO2 nanoparticles were initially prepared via a sol-gel method and afterwards combined with optimum amounts of graphitic carbon nitride (g-C3N4) by a hydrothermal procedure to finally produce TiO2/g-C3N4 heterostructures. TiO2/g-C3N4 was impregnated with a silver nitrate aqueous solution containing sodium citrate as a reducing agent resulting in elemental silver nanoparticle (Ag0 NP) integration, as confirmed by x-ray photoelectron spectroscopy (XPS). Following crystallographic, electron-microscopy and spectroscopic characterization, the prepared nanocomposites presented high photocatalytic activity for both oxidation and reduction reactions. The photodegradation of model organic pollutants: methylene blue (MB) and rhodamine B (RhB) dyes and oxytetracycline (OTC) pharmaceutical, together with decomposition of 4-nitrophenol (4-NP) and Cr(VI), was investigated and the reaction constants were determined. An optimum component ratio was determined, which leads to the effective elimination of pollutants under UV light, with degradation percentages up to 95% for MB and 89% for RhB and 90% removal efficiency of the OTC pharmaceutical. The degradation of both dyes was also confirmed under artificial solar light. Furthermore, the ternary TiO2/g-C3N4@Ag NCs were highly effective for the photocatalytic reduction of 4-NP to aminophenol (>95%) and Cr(VI) to Cr(III) (80%), under UV illumination.

Keywords

• Bifunctional photocatalysts
• Oxidation and reduction reactions
• Industrial pollutants degradation
• UV and Artificial solar light