TiO₂−Graphene Nanocomposites for Gas-Phase Photocatalytic Degradation of Volatile Aromatic Pollutant: Is TiO₂−Graphene Truly Different from Other TiO₂−Carbon Composite Materials?

Abstract

The nanocomposites of TiO(2)-graphene (TiO(2)-GR) have been prepared via a facile hydrothermal reaction of graphene oxide and TiO(2) in an ethanol-water solvent. We show that such a TiO(2)-GR nanocomposite exhibits much higher photocatalytic activity and stability than bare TiO(2) toward the gas-phase degradation of benzene, a volatile aromatic pollutant in air. By investigating the effect of different addition ratios of graphene on the photocatalytic activity of TiO(2)-GR systematically, we find that the higher weight ratio in TiO(2)-GR will decrease the photocatalytic activity. Analogous phenomenon is also observed for the liquid-phase degradation of dyes over TiO(2)-GR. In addition, the key features for TiO(2)-GR including enhancement of adsorptivity of pollutants, light absorption intensity, electron-hole pairs lifetime, and extended light absorption range have also been found in the composite of TiO(2) and carbon nanotubes (TiO(2)-CNT). These strongly manifest that TiO(2)-GR is in essence the same as other TiO(2)-carbon (carbon nanotubes, fullerenes, and activated carbon) composite materials on enhancement of photocatalytic activity of TiO(2), although graphene by itself has unique structural and electronic properties. Notably, this key fundamental question remains completely unaddressed in a recent report ( ACS Nano 2010 , 4 , 380 ) regarding liquid-phase degradation of dyes over the TiO(2)-GR photocatalyst. Thus, we propose that TiO(2)-GR cannot provide truly new insights into the fabrication of TiO(2)-carbon composite as high-performance photocatalysts. It is hoped that our work could avert the misleading message to the readership, hence offering a valuable source of reference on fabricating TiO(2)-carbon composites for their application as a photocatalyst in the environment cleanup.

Graphene based metal and metal oxide nanocomposites: synthesis, properties and their applications

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Origin and Perspectives of the Photochemical Activity of Nanoporous Carbons

“…This effect is mainly explained by the graphene phase providing electrical conductivity, separating charge carrier, and delaying their recombination. However, the beneficial effect of the use of graphene for photocatalytic purposes is still quite controversial, and has been recently argued that its enhancing role in the photocatalytic activity of TiO 2 /graphene composites is in essence the same as that of any other carbon material 25. Here, it is important to mention that in fact the addition of an amorphous carbon phase to semiconductor for increasing the photoactivity was initiated well before the graphene discovery 14, 26, 27…”

Metal–Organic Frameworks as Promising Photosensitizers for Photoelectrochemical Water Splitting

“…Among the various studied materials, titanium dioxide (TiO 2 ) has attracted the greatest attention due to its nontoxicity, physical and chemical stability, and peculiar electronic and optical properties 2. However the wide band gap of TiO 2 limits its absorption of visible light, which restricts the solar energy conversion efficiency.…”