Unprecedented photocatalytic activity and durability of Pt/TiO2 for decomposing persistent organic pollutants (e.g. benzene) have been obtained by adding trace H2 into an O2-rich photooxidation system.

Sol-gel prepared mixtures of silica or zirconia with titania are shown to have significantly higher activities than pure titania for the complete photocatalytic oxidation of ethylene. These higher activities are only apparentwhen the respective catalysts are stabilized by sintering. The differences become even more pronounced when the catalysts are used in a tubular reactor. Optimum mixture concentrations are found to be 12 wt % zirconia and 16 wt % silica in titania. Both catalyst types exhibit activity maxima with respect to sintering temperature. It is hypothesized that the maxima arise from opposing effects of densification and phase transformation versus beneficial sintering. A comparison of our catalyst compositions with literature in this area suggests that the increase in activity due to the addition of silica or zirconia may be a result of higher surface acidity. However, isoelectric point measurements employing the unsintered and sintered catalysts show no conclusive increase in surface acidity. The effects of sintering temperature on the surface area, porosity, and crystal structure of the catalysts are also presented.

A porous β-Ga2O3 photocatalyst has been successfully prepared. The photocatalyst was characterized by XRD, N2 adsorption-desorption, TEM, UV/vis, and FTIR techniques. The photocatalytic activity of the sample was evaluated by the decomposition of benzene in air under UV light illumination and was compared with that of the commercial titania [Degussa P25] and Pt/P25. Results revealed that the synthesized Ga2O3 was porous β-Ga2O3 and was highly photoactive for mineralizing benzene and its derivatives [e.g., toluene and ethylbenzene] to CO2 under ambient conditions. The photocatalytic conversion of benzene over β-Ga2O3 was about 1 order of magnitude higher than that over P25, and no obvious deactivation of β-Ga2O3 was observed during the prolonged operation of 80 h. The high activity and long-term stability of the Ga2O3 have been ascribed to its stronger oxidative capability and higher specific surface area in comparison with P25.

Stable crystalline CdS nanoparticles were synthesized in Nafion ionomer membranes by using thioacetamide (TAA) as a nonionic precursor. Unlike the ionic precursors such as Na2S, TAA could diffuse into the cationic-exchangeable ionomer membranes much more uniformly. This led to the formation of homogeneously distributed CdS nanoparticles in the Nafion membranes, which was confirmed by elemental mapping with energy-dispersive X-ray (EDAX) analysis. Results from the characterizations on the physical properties, the chemical stability, and the photocatalytic properties of these CdS nanoparticles embedded in Nafion membranes are presented and discussed. The parallel data from the CdS nanoparticles in Nafion membranes prepared from the ionic Na2S precursor are also shown for comparison.

TiO2 fibers were fabricated through heat treatment of titanium alkoxide dissolved in a solvent (ethanol and toluene) under autogenous pressure, using activated carbon fibers as templates. For comparison, a supercritical CO2 process was also employed. The difference in the solvent’s affinity for water led to a large difference in the morphology of TiO2 fibers produced. Moreover, the fibers synthesized using toluene in our relatively mild conditions exhibited a similar pore size distribution and surface area to those made using supercritical CO2.