The photooxidation of methanol, n-hexane and carbon monoxide using TiO 2nanotubes (TNTs) has been investigated by a new IR-operando technique. Following the photocatalytic reaction by time resolved IR spectroscopy coupled with mass spectrometry (MS) allowed a surface study of the photocatalyst with on line analysis of the products. The identification of the species adsorbed on the photocatalyst surface and those detected in the gas phase led to further clarify the photooxidation mechanisms. The characterization of the photocatalyst has been performed by IR, Raman, UV-visible, XRD, N 2 -sorption, SEM and TEM techniques. The activity and selectivity of the photocatalyst have been determined by quantitative studies using gas-IR and MS. For comparison, photooxidation reactions, using TiO 2 -P25 as reference, have been performed under the same conditions. The influence of different parameters such as temperature, VOC concentrations and UV irradiation intensities on the reactivity and selectivity of the photocatalytic reaction has been investigated. The 2 temperature effect has been shown by TPD measurements (from RT to 200°C). The TNTs material showed a higher reactivity and CO 2 -selectivity in comparison with TiO 2 -P25.

Anatase nanosheets with exposed {001} facets have gained increasing interest for photocatalytic applications. To fully understand the structure-to-activity relation, combined experimental and computational methods have been exploited. Anatase nanosheets were prepared under hydrothermal conditions in the presence of fluorine ions. High resolution scanning transmission electron microscopy was used to fully characterize the synthesized material, confirming the TiO 2 nanosheet morphology. Moreover, the surface structure and composition of a single nanosheet could be determined by annular bright-field scanning transmission electron microscopy (ABF-STEM) and STEM electron energy loss spectroscopy (STEM-EELS). The photocatalytic activity was tested for the decomposition of organic dyes rhodamine 6G and methyl orange and compared to a reference TiO 2 anatase sample. The anatase nanosheets with exposed {001} facets revealed a significantly lower photocatalytic activity compared to the reference. In order to understand the mechanism for the catalytic performance, and to investigate the role of the presence of F − , light-induced electron paramagnetic resonance (EPR) experiments were performed. The EPR results are in agreement with TEM, proving the presence of Ti 3+ species close to the surface of the sample and allowing the analysis of the photoinduced formation of paramagnetic species. Further, ab initio calculations of the anisotropic effective mass of electrons and electron holes in anatase show a very high effective mass of electrons in the [001] direction, having a negative impact on the mobility of electrons toward the {001} surface and thus the photocatalysis. Finally, motivated by the experimental results that indicate the presence of fluorine atoms at the surface, we performed ab initio calculations to determine the position of the band edges in anatase slabs with different terminations of the {001} surface. The presence of fluorine atoms near the surface is shown to strongly shift down the band edges, which indicates another reason why it can be expected that the prepared samples with a large amount of {001} surface, but with fluorine atoms near the surface, show only a low photocatalytic activity.

Analysis methods that require small volumes of aqueous samples can be of large benefit for applications when expensive chemicals are involved or available volumes are substantially small and concentrations are low. A new method is presented to allow microvolume liquid injections on TOC equipment using a special designed Shimadzu gas injection kit ® in combination with a high precision syringe and Chaney adapter. Next to details on the methodology of microvolume TOC injections, the technique is shown to be beneficial to evaluate the efficiency of photocatalytic dye degradation on titania materials in terms of CO 2 conversion simultaneously with classic UV-Vis analysis measurements within a lab scale photocatalytic test setup (volume <100 mL). The possibility to allow multiple microvolume samplings in short time intervals during several hours without a substantial decrease in volume/catalyst ratio is of particular value for the evaluation of photocatalysts. By combining both techniques at short time intervals, additional knowledge of the degradation process/mechanism, kinetics and the efficiency can be obtained in a direct way. Moreover, the developed μV-TOC analysis is specifically useful in those applications in which low sample volumes in combination with low concentrations are involved. For example, μV-TOC can similarly be put into service in a wide range of small volume setups, e.g., analytes from high-throughput screening, pharmaceutical applications and other advanced oxidation processes that formally could not be analyzed due to limited sample volumes and often low concentrations. OPEN ACCESSCatalysts 2013, 3 75

a b s t r a c tHighly ordered SBA-15-type ethane-bridged PMOs have been obtained by employing H 3 PO 4 as acid to tune the pH in the presence of copolymer surfactant P123. The effects of the acidity and the addition of inorganic salt on the formation of the mesostructure are investigated. It is found that, compared with HCl, the polyprotic weak acid H 3 PO 4 is preferable for the synthesis of highly ordered SBA-15-type ethane-bridged PMOs with larger pore size and surface areas under mild acidic conditions. Moreover, taking the advantages of the mild acidic condition, vanadium-containing SBA-15-type ethane-bridged PMOs were successfully prepared through a direct synthesis approach. The XRD, N 2 -sorption, UVeVis and CW-EPR studies of the V-PMO show that part of the vanadium species are present in polymeric (VeO eV) n clusters, while part of the vanadium centers are well-dispersed and immobilized on the inner surface of the mesopores.

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