Photocatalysis

About: Photocatalysis is a research topic. Over the lifetime, 67088 publications have been published within this topic receiving 2145233 citations. The topic is also known as: photocatalyst.

Self-Assembling TiO2 Nanorods on Large Graphene Oxide Sheets at a Two-Phase Interface and Their Anti-Recombination in Photocatalytic Applications

Abstract: TiO 2 nanorods are self-assembled on the graphene oxide (GO) sheets at the water/toluene interface. The self-assembled GO–TiO 2 nanorod composites (GO–TiO 2 NRCs) can be dispersed in water. The effective anchoring of TiO 2 nanorods on the whole GO sheets is confi rmed by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), and thermogravimetric analysis (TGA). The signifi cant increase of photocatalytic activity is confi rmed by the degradation of methylene blue (MB) under UV light irridiation. The large enhancement of photocatalytic activity is caused by the effective charge anti-recombination and the effective absorption of MB on GO. The effective charge transfer from TiO 2 to GO sheets is confi rmed by the signifi cant photoluminescence quenching of TiO 2 nanorods, which can effectively prevent the charge recombination during photocatalytic process. The effective absorption of MB on GO is confi rmed by the UV-vis spectra. The degradation rate of MB in the second cycle is faster than that in the fi rst cycle because of the reduction of GO under UV light irradiation.

Reduction of aryl halides by consecutive visible light-induced electron transfer processes

Abstract: Biological photosynthesis uses the energy of several visible light photons for the challenging oxidation of water, whereas chemical photocatalysis typically involves only single-photon excitation. Perylene bisimide is reduced by visible light photoinduced electron transfer (PET) to its stable and colored radical anion. We report here that subsequent excitation of the radical anion accumulates sufficient energy for the reduction of stable aryl chlorides giving aryl radicals, which were trapped by hydrogen atom donors or used in carbon-carbon bond formation. This consecutive PET (conPET) overcomes the current energetic limitation of visible light photoredox catalysis and allows the photocatalytic conversion of less reactive chemical bonds in organic synthesis.

Enhanced photocatalytic H₂-production activity of graphene-modified titania nanosheets.

Abstract: Graphene-modified TiO2 nanosheets with exposed (001) facets (graphene/TiO2) were prepared by microwave-hydrothermal treatment of graphene oxide (GO) and hydrothermally synthesized TiO2 nanosheets with exposed (001) facets in an ethanol–water solvent. These nanocomposite samples showed high photocatalytic H2-production activity in aqueous solutions containing methanol, as sacrificial reagent, even without Pt co-catalyst. The optimal graphene content was found to be ∼1.0 wt%, giving a H2-production rate of 736 μmol h−1 g−1 with a quantum efficiency (QE) of 3.1%, which exceeded the rate observed on pure TiO2 nanosheets by more than 41 times. This high photocatalytic H2-production activity is due to the deposition of TiO2 nanosheets on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers. The observed enhancement in the photocatalytic activity is due to the lower absolute potential of graphene/graphene˙− (−0.08 V vs. SHE, pH = 0) in comparison to the conduction band (−0.24 V) of anatase TiO2, meanwhile the aforementioned absolute value is higher than the reduction potential of H+ (0 V), which favors the electron transfer from the conduction band (CB) of TiO2 to graphene sheets and the reduction of H+, thus enhancing photocatalytic H2-production activity. The proposed mechanism for the observed photocatalytic performance of TiO2 nanosheets, modified with a small amount of graphene, was further confirmed by photoluminescence spectroscopy and transient photocurrent response. This work not only shows a possibility for the utilization of low cost graphene sheets as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also for the first time shows a significant enhancement in the H2-production activity by using metal-free carbon material as an effective co-catalyst.

Improving carbon nitride photocatalysis by supramolecular preorganization of monomers.

Abstract: Here we report a new and simple synthetic pathway to form ordered, hollow carbon nitride structures, using a cyanuric acid–melamine (CM) complex in ethanol as a starting product. A detailed analysis of the optical and photocatalytic properties shows that optimum hollow carbon nitride structures are formed after 8 h of condensation. For this condensation time, we find a significantly reduced fluorescence intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes. Enhanced charge transfer is seen as well from a drastic increase of the photocatalytic activity in the degradation of rhodamine B dye, which is shown to proceed via photoinduced hole transfer. Moreover, we show that various CM morphologies can be obtained using different solvents, which leads to diverse ordered carbon nitride architectures. In all cases, the CM-C3N4 structures exhibited superior photocatalytic activity compared to the bulk material. The utilization of C...

Graphite Oxide as a Photocatalyst for Hydrogen Production from Water

Abstract: A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4–4.3 eV is synthesized by a modified Hummers' procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42 nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20 vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination.