Constructing BiVO4/Graphene/TiO2 nanocomposite photoanode for photoelectrochemical conversion applications

• TiO2 photoanode modified by BiVO4/Graphene was synthesized on FTO.
• The photocurrent density of BiVO4/Graphene/TiO2 photoanode was 1.30 A/m2.
• The BiVO4/Graphene nanocomposite enhanced light absorption and charge separation.
• A charge transfer mechanism was proposed to understand the enhanced PEC activity.

BiVO4/Graphene/TiO2 as a novel nanocomposite photoanode was designed, synthesized and characterized for photoelectrochemical application. BiVO4/Graphene nanocomposite was initially synthesized by photocatalytic process and then, BiVO4/Graphene/TiO2 nanocomposite thin film was prepared by deposition of the BiVO4/Graphene solution onto the surface of sol–gel derived TiO2 thin film. Morphology, crystal structure, surface chemical composition and optical properties of the synthesized BiVO4/Graphene/TiO2 nanocomposite thin film were characterized and compared with the BiVO4/Graphene and pure TiO2 samples. Observations of scanning electron microscopy (SEM) images revealed that the surface of the TiO2 thin film was modified by the BiVO4/Graphene with high surface area. According to X-ray diffraction (XRD) analysis, formation of anatase and monoclinic phase was confirmed for crystalline structure of TiO2 and BiVO4, respectively. UV–visible absorption spectra of the samples showed that the absorption edge and intensity of the BiVO4/Graphene/TiO2 nanocomposite film were increased with respect to the TiO2 film. The BiVO4/Graphene/TiO2 nanocomposite photoanode yielded a photocurrent density of ∼ 1.30 A/m2 as compared to 0.27 A/m2 for the TiO2 at 0.8 V vs Ag/AgCl under UV–visible irradiation in similar condition. The improved photoelectrochemical activity is believed due to the enhanced light absorption and higher surface area of BiVO4/Graphene as well as better charge transfer of the photogenerated carriers at the BiVO4/Graphene/TiO2 interfaces via Graphene.