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The use of graphene-based materials as co-catalysts are explored in the production of active filter media for methanol gas-phase photo-oxidation. The present work is intended to show the relationship between the composition and the morphology of the photocatalytic systems with the performance of nanostructured mats. Three different graphene-based co-catalysts have been used (graphene oxide, reduced graphene oxide, and few-layer graphene) and the effect of the different degrees of oxidation has been explored. The comparison of the obtained results has revealed that the structure of the media united with the affinity of the graphene-based co-catalysts with the polymer matrix, strongly affect the photocatalytic efficiency. The reduced graphene oxide has given the best performance, in terms of a higher rate of gas-phase methanol degradation, thanks to the enhanced electron mobility ensured by its deep contact with the photocatalyst itself. [ABSTRACT FROM AUTHOR]

The abatement of organic pollutants by TiO2 photocatalysis has been established as one of the benchmark applications of advanced oxidation processes for both liquid and gas phase purification. Such solution is particularly suitable for indoor air pollution where volatile organic compounds (VOCs) represent a class of chemicals of high concern for their adverse effects on both environment and human health. However, different shortcomings still affects TiO2 photocatalytic performance in terms of weak adsorptivity and fast electron-hole recombination, limiting its applicability. As a result, different strategies have been investigated over the last years in order to promote a higher TiO2 photo-efficiency. In this study we used electrospun (PVDF) nanofibers as a support for the photo catalytic system obtained by coupling graphene based materials and TiO2 during solvothermal synthesis. The resultant nanostructured membranes have been tested for acetaldehyde and methanol degradation under UV light showing an increase in the photocatalytic activity compared to bare TiO2. Such results may be ascribed to the decrease of band-gap energy and to increased electron mobility in the photocatalytic nanocomposite. [ABSTRACT FROM AUTHOR]

In this study we evaluated the effect of microwave vacuum plasma for the surface functionalization of graphitic fillers (graphite and graphene); we also showed the effect of the functionalization on the mechanical and electrical properties of epoxy composites. Optimized conditions of plasma treatment were defined to obtain high plasma density and increased surface hydrophilicity of the fillers, with high stability of functionalization over time and temperature. However, the extent of such treatments proved to be limited by the high temperatures involved in the curing process of the resin. The use of specific gas mixtures (He/O2) during functionalization and the use of a high surface filler (graphene) can partially limit these negative effects thanks to the higher thermal stability of the induced functionalization. As a consequence, mechanical tests on graphene filled epoxies showed limited improvements in flexural properties while electrical resistivity is slightly increased with a shift of the percolation threshold towards higher filler concentration. [ABSTRACT FROM AUTHOR]

The present work examines the influence of different carbon-based fillers on the performance of electrically conductive polymer blend composites. More specifically, we examined and compared the effects of graphene (GR), carbon nanotubes (CNTs) and carbon black (CB) on a PC/ABS matrix by morphological investigation, electrical and physic-mechanical characterization. Electrical analyses showed volume resistivity decreased when the CNTs and CB content were increased, although the use of melt-mixed GR did not really influence this property. For the latter, solution blending was found to be more suitable to obtain better GR dispersion, and it obtained electrical percolation with a graphene content ranging from 0.5% to 1% by weight, depending on the solvent removal method that was applied. There was a gradual improvement in all of the composites' dielectric properties, in terms of loss factor, with temperature and the concentration of the filler. As expected, the use of rigid fillers increased the composite stiffness, which is reflected in a continuous increment in the composites' modulus of elasticity. The improvements in tensile strength and modulus were coupled with a reduction in impact strength, indicating a decrease in polymer toughness and flexibility. TEM micrographs allowed us to confirm previous results from studies on filler dispersion. According to this study and the comparison of the three carbon-based fillers, CNTs are the best filler choice in terms of electrical and mechanical performance. [ABSTRACT FROM AUTHOR]

Abstract The presence of volatile organic compounds released at significantly high concentration levels from livelihood sources entails more and more the development of effective active filter media for their control and abatement within indoor environments. Nanostructured nonwoven mats, obtained by combination of electrodynamic technologies (electrospinning and electrospraying), were produced and characterized by SEM and TGA methods. TiO 2 was the main photocatalyst, whereas Graphene and cyclodextrins were used as co-catalyst and sorption components, respectively. The photocatalytic activities of all the samples were tested in the gas-phase photocatalytic oxidation (PCO) reaction of acetaldehyde, methanol and n-hexane in a static reactor by the FT-IR in situ method. The influence of the production approach, the chemical structure of the pollutants and the testing unit layouts, were evaluated. Filtering media produced by performing alternatively electrospinning of polymeric support and electrospraying of photocatalyst nanoparticles, led a 96% acetaldehyde (C 0 = 133 ppm) abatement after 30 min. with a half time of 9 min. with the PAN + TiO 2. Further reduction of the half-time was achieved with a particular corrugated sheets configuration, wherein the testing unit was able to treat 6.4 m3/h of air. The proposed system showed good versatility in terms of photodegradation of different pollutants (methanol and n-hexane) both pure and in mixture. [ABSTRACT FROM AUTHOR]