Comparative study of metal nanoparticles anchored TiO2 using polyoxometalate intermediate in photodegradation of azo dye pollutant in aquatic environments

Abstract

Herein, metal nanoparticles (Au, Ag, and Pt) are locally deposited on TiO2 with an UV-switchable polyoxometalate intermediate to achieve highly active photocatalyst nanohybrids. The successful preparation of these nanohybrids was confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Zeta potential (ZP), and UV–visible spectroscopy. TEM images showed the anchoring of metal nanoparticles of an average size of 20 nm on the TiO2 surface. A comparative study revealed that the bandgap energy was reduced in the order of Pt@PW-TiO2 (2.90 eV) > Ag@PW-TiO2 (2.95 eV) > Au@PW-TiO2 (3.05 eV). Likewise, the photocatalytic efficiency of fabricated nanohybrids was investigated in the degradation of reactive blue 19 (RB19), an azo dye model, under UV–visible light illumination and different experimental conditions. Optimal photodegradation occurred at pH = 3.8 with 0.33 gL−1 of photocatalyst exposed to light for 60 min. Under optimal conditions, the maximum and minimum photodegradation abilities were observed using Pt and Au deposited hybrids. A kinetic study of RB19 photodegradation was also conducted, resulting in pseudo-first order reaction rate constants of 0.0203, 0.025, and 0.0808 min−1, respectively, for the Au@PW-TiO2, Ag@PW-TiO2, and Pt@PW-TiO2 nanohybrids. Finally, the most probable mechanism for RB19 degradation using prepared photocatalysts is presented.