Enriched photocatalytic degradation of methylene blue by reduced graphene oxide supported gold titania nanocomposite

A facile co-precipitation method was employed for the synthesis of reduced graphene oxide-supported gold -doped titania nanocomposite. The surface morphology (SEM) confirms the uniform distribution of nanoparticles on the reduced graphene oxide support and crystallinity study (XRD) verified the anatase phase of TiO2. The UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence (PL) experiments confirmed the decrease in ideal band gap energy of TiO2 towards red shift. The red shift of band gap energy from bare TiO2 catalyst (2.72 eV) to Au-TiO2 catalyst (1.9 eV) and further to reduced graphene supported Au-TiO2 catalyst (1.76 eV) demonstrates a pronounced greater absorption aptitude of the reduced graphene supported Au-TiO2 catalyst over an extensive range of the visible spectrum. Further, reduced graphene oxide supported Au-TiO2 catalyst exhibited superior photocatalytic degradation (90%) toward methylene blue (MB) than Au-TiO2 catalyst (65%) and bare TiO2 catalyst (35%) within 90 minutes. This excellent enhanced red shift photocatalytic activity may be attributed to the introduction of new energy levels, surface plasmon resonance (SPR) effect of gold nanoparticles and Schottky junction formation relationship between the gold and titania interface. Methylene blue is degraded to nontoxic molecules by the effects of hydroxide (OH−) and superoxide (O2−) active radicals. Again, reduced graphene supported Au-TiO2 composites possess better reusability stability than other two photo-catalysts.