Enhanced visible photocatalytic activity of nanocrystalline alpha-Fe2O3 by coupling phosphate-functionalized graphene

In this work, it is clearly demonstrated that the visible photocatalytic activity for degrading colorless gas-phase acetaldehyde and liquid-phase phenol of nanocrystalline alpha-Fe2O3, which is synthesized by a phase-separated hydrolysis-solvothermal method, is greatly enhanced by coupling with an appropriate amount of unfunctionalized and phosphate-functionalized graphene, especially the latter. It is suggested that the enhanced activity can be attributed to the obviously increased amount of adsorbed O-2 so as to promote photogenerated charge separation, as verified mainly by means of atmosphere-controlled surface photovoltage spectra, transient state surface photovoltage responses, O-2 electrochemical reduction measurements, and O-2 temperature-programmed desorption curves. The coupled graphene is favorable for photogenerated electrons to transfer and then separate in space. This work provides a feasible route to improve photocatalytic activity for degrading pollutants using composites of nanostructured carbon and oxides.