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

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.

Automated summary

Phosphotungstic acid and triethylenetetramine-modified graphene oxide self-assembled to form polyoxometalate-graphene composites via electrostatic interaction. The structure and morphology of the photocatalyst were analyzed using various techniques, indicating that HPW nanoparticles are anchored on the AGO sheets. The composite exhibited excellent photocatalytic activity, with hydroxyl radicals and holes as the main active species.