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The photocatalytic activity of two commercial titanium dioxide powders (Cristal Global, Millennium PC500 and Evonik, P25) is compared towards acetaldehyde degradation in the gas phase. In contrast to the extensive literature available, we found a higher activity for the PC500 than for the P25 coating. Here, we present a comprehensive characterization of the bulk and surface properties of both powders. Our comparison shows that the material properties that dominate the overall photocatalytic activity in gas phase differ from those required for the photodegradation of water-borne pollutants.

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We present a novel manufacture route for silica-titania photocatalysts using the diatom microalga Pinnularia sp. Diatoms self-assemble into porous silica cell walls, called frustules, with periodic micro-, meso- and macroscale features. This unique hierarchical porous structure of the diatom frustule is used as a biotemplate to incorporate titania by a sol-gel methodology. Important material characteristics of the modified diatom frustules under study are morphology, crystallinity, surface area, pore size and optical properties. The produced biosilica-titania material is evaluated towards photocatalytic activity for NOx abatement under UV radiation. This research is the first step to obtain sustainable, well-immobilised silica-titania photocatalysts using diatoms.

The concept of an all-gas-phase photoelectrochemical (PEC) cell producing hydrogen gas from volatile organic contaminated gas and light is presented. Without applying any external bias, organic contaminants are degraded and hydrogen gas is produced in separate electrode compartments. The system works most efficiently with organic pollutants in inert carrier gas. In the presence of oxygen, the cell performs less efficiently but still significant photocurrents are generated, showing the cell can be run on organic contaminated air. The purpose of this study is to demonstrate new application opportunities of PEC technology and to encourage further advancement toward PEC remediation of air pollution with the attractive feature of simultaneous energy recovery and pollution abatement.