Synthesis of mesoporous titania–graphite composite templated by hypocrellins for visible-light photocatalytic degradation of acetaldehyde

A photoactive compound extracted from a fungus (Hypocrella bambuase), named hypocrellins, was used as template to synthesize thermally stable mesoporous materials. The synthesized mesoporous titania samples were characterized using a combination of various physicochemical techniques, such as N2 adsorption/desorption measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The results of physicochemical characterizations showed that the as-synthesized sample was a composite of highly crystalline mesoporous anatase titania and graphitic carbon (gc–MTiO2), which implies the dual function of hypocrellins as template and “dopant”. The in situ doped graphitic carbon significantly increased the visible-light absorbance of TiO2. The gc–MTiO2 exhibited efficient photocatalytic activity under visible-light for photodegradation of acetaldehyde, a common indoor air pollutant. The photophysics and electron dynamics in this photocatalytic process were studied by time-resolved FT-IR spectra, in particular on the nano- to milli-second time scale. It is observed that electrons were injected into the conduction band of gc–MTiO2 and they were decayed to deep traps caused by graphitic carbon. The reported strategies could open up new uses for mesoporous titania self-doped with carbon in applications such as solar cells, photocatalysts, photoelectrical devices, and photo-induced sensors.