The assembly of polyoxometalate-graphene oxide composites for photocatalytic removal of organic dye in water

The catalyst is prepared by combining modified graphene oxide with phosphotungstic acid by electrostatic adsorption, which exhibits excellent photocatalytic performances for the degradationof methylene blue. The free radical trapping experiments show that the holes and hydroxyl groups play a major role in the photocatalytic degradation process. [Display omitted] •Phosphotungstic acid (HPW) and graphene oxide modified with triethylenetetramine were self-assembled via electrostatic interaction to form polyoxometalate-graphene composites.•Under Xe lamp irradiation as a simulated sunlight source, the AGO-HPW-10 composite shows the effective photocatalytic activity in the degradation of MB solution.•The free radical trapping experiments showed that hydroxyl radicals and holes are the main active species during photocatalytic reaction process.•The energy band structure of the AGO-HPW-10 indicates that the introduction of AGO is favorable for the spatial separation of electrons and holes. Phosphotungstic acid (HPW) and graphene oxide modified with triethylenetetramine (AGO) were self-assembled via electrostatic interaction to form polyoxometalate-graphene composites. The structure and morphology of the photocatalyst were investigated by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM), which revealed that HPW nanoparticles are anchored on the AGO sheets. Methylene blue (MB) solution (100 mL 20 mg/L) was used as a model to investigate the catalytic activity and mechanism of this photocatalyst under 300 W Xenon lamp as simulated sunlight source. The results showed that AGO-HPW-10 exhibited excellent photocatalytic activity (25 mg catalyst, the removal rate of MB is 84.02% within 150 min). The free radical trapping experiments showed that hydroxyl radicals and holes are the main active species during photocatalytic reaction process. Mulliken electronegativity principle, ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) and electrochemical voltammetry linear sweep (LSV) technique indicated that the energy band structure of the photocatalyst is favorable for the spatial separation of electrons and holes.