Pt-TiO2/graphene photocatalysts for degradation of AO7 dye under visible light

Abstract

In this work, the hydrothermal method was used for synthesizing Pt-TiO2/graphene nanocomposites. Obtained Pt-TiO2/graphene photocatalysts were characterized by Raman spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, photoluminescence spectroscopy, and UV–vis spectroscopy. The photocatalytic activity of the Pt-TiO2/graphene nanocomposite catalyst was assessed by examining the degradation of acid orange 7 (AO7) dye from aqueous solutions as a probe reaction under solar light irradiations. X-ray photoelectron spectroscopy analyses showed that the Pt ions substituted in the TiO2 lattice were present mainly in the Pt(II) state. Pt-TiO2/graphene exhibited higher photocatalytic activities than TiO2/graphene under visible light irradiation. The visible light activity of Pt-TiO2/graphene was strongly affected by the calcination temperature and the amounts of H2PtCl6, which were optimal at 500°C and 10% H2PtCl6, respectively. The degradation efficiency of the Pt-TiO2/graphene nanocomposite was 99% after 6h of visible light irradiation. The enhanced photodegradation activity might be mainly attributed to the role of Pt-TiO2 as a charge generating center and graphene played as electron acceptor and transporter in the nanocomposite, which effectively suppressed the charge recombination and promoted the charge transfer within the composite.