Enhancing the photocatalytic activity of TiO2 co-doping of graphene–Fe3+ ions for formaldehyde removal

•We successfully synthesize graphene–TiO2 and graphene/Fe3+–TiO2 at relatively low temperature (100 °C).•The photocatalytic activity of graphene–TiO2 and graphene/Fe3+–TiO2 is studied under UV and visible light irradiation.•The effect of graphene and Fe3+ dopant on TiO2 photocatalyst is discussed.•Graphene/Fe3+–TiO2 photocatalyst exhibits greater photocatalytic activity than that of graphene–TiO2 and TiO2.

In the present work, graphene and Fe3+ ions were doped to enhance the photocatalytic activity of a TiO2 photocatalyst with the expectation of synergistic effects on the specific surface area and electronic conductivity due to the formation of Ti–O–C bonds preventing charge recombination contributed by graphene and band gap energy narrowing by doping with Fe3+ ions. GR/Fe3+–TiO2 was successfully synthesized by the refluxed peroxo titanic acid (PTA) method and was tested for gaseous formaldehyde removal. The results show that graphene contributed to formaldehyde adsorption since the equilibrium adsorption capacity increased with an increasing weight ratio of graphene. The GR/Fe3+–TiO2 photocatalyst with a weight ratio of graphene to TiO2 (PTA) of 1:50 and the Fe3+ dopant at 0.12 wt% was optimal. An equilibrium formaldehyde adsorption capacity of 10.2 mg(HCHO) g−1catalyst and photodegradation efficiency of about 50.3% and 25.5% under UV and visible light irradiation for 90 min, respectively, were obtained. It was observed that the adsorption property of the catalyst was increased by adding graphene and the extendable absorption edge of light to longer wavelengths was attributed to the synergistic effect of graphene and Fe3+ dopants on the band gap energy of the catalyst. The greater photocatalytic activity of GR/Fe3+–TiO2 compared to GR–TiO2 resulted from more hydroxyl (OH) and superoxide (−O2)(O2−) radicals produced via redox reactions with Fe ions.