Cataldo Simari

Cationic and anionic azo-dye removal from water by sulfonated graphene oxide nanosheets in Nafion membranes

Graphene oxide flakes functionalized with 3-amino-1-propanesulfonic acid (denoted as GOSULF) as a powder or incorporated into an ionomer membrane such as Nafion (DuPont) were studied for water purification applications. The adsorption and the photocatalytic activity of the GOSULF powder itself or confined as a nano-additive in the membrane (Nafion–GOSULF) were investigated by measuring the degradation of a cationic dye, methylene blue (MB), in the dark and under UV/Visible light illumination. The results were compared with the ability of these systems to degrade an anionic dye, methyl orange (MO), in order to evaluate the role of the polymer–dye interaction. The degradation of the azo dyes depends on the mutual interaction between GOSULF flakes, the polymeric matrix and the dye: Nafion–GOSULF strongly reduces MB both under dark and illumination conditions in the same way as the GOSULF powder, while, for MO degradation, the composite membrane is more efficient than GOSULF alone. Finally, the possibility of reusing the same photocatalytic material several times, which is the main advantage of embedding active nanomaterials in a polymer matrix, is demonstrated by the effective regeneration of the nanocomposite membranes.

Composite Gel Polymer Electrolytes Based on Organo-Modified Nanoclays: Investigation on Lithium-Ion Transport and Mechanical Properties

Composite gel polymer electrolytes (GPEs) based on organo-modified montmorillonite clays have been prepared and investigated. The organo-clay was prepared by intercalation of CTAB molecules in the interlamellar space of sodium smectite clay (SWy) through a cation-exchange reaction. This was used as nanoadditive in polyacrylonitrile/polyethylene-oxide blend polymer, lithium trifluoromethanesulphonate (LiTr) as salt and a mixture of ethylene carbonate/propylene carbonate as plasticizer. GPEs were widely characterized by DSC, SEM, and DMA, while the ion transport properties were investigated by AC impedance spectroscopy and multinuclear NMR spectroscopy. In particular, 7Li and 19F self-diffusion coefficients were measured by the pulse field gradient (PFG) method, and the spin-lattice relaxation times (T1) by the inversion recovery sequence. A complete description of the ions dynamics in so complex systems was achieved, as well as the ion transport number and ionicity index were estimated, proving that the smectite clay surfaces are able to “solvatate” both lithium and triflate ions and to create a preferential pathway for ion conduction.

A facile approach to fabricating organosilica layered material with sulfonic groups as an efficient filler for polymer electrolyte nanocomposites

We report the one-pot synthesis of a siliceous layered material bearing sulfonic group functionalities through the simple sol–gel process of 3-(trihydroxy silyl) propyl-1-propane-sulfonic acid. This easy-fabricated layered nanomaterial can possess a high number of organo-sulfonic groups, rendering it an attractive, multifunctional filler for polymer electrolyte nanocomposites for energy applications such as lithium batteries and fuel cells. X-ray diffraction and photoelectron spectroscopy confirm the layered structure and the presence of sulfonic groups, respectively. In the present work, the silica nanomaterial was tested as a nanofiller for the development of innovative Nafion nanocomposite membranes for proton exchange membrane fuel cells (PEMFCs). Pristine functional material and nanocomposites were characterized by a combination of analytical techniques. The dynamic mechanical analysis showed that composite membranes are much stiffer and can withstand higher temperatures than recast Nafion membrane. Proton transport properties and water management were investigated by 1H pulsed field gradient (PFG) NMR spectroscopy, by measuring the water self-diffusion coefficients in a wide temperature range (20–130 °C). The data showed a remarkable high water retention capacity of composite membranes and high proton diffusion in the temperature region above 100 °C, representing a significant advance in the current state-of-the-art technology of PEMFCs.