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Abstract: Polyvinylalcohol–mordenite (PVA–MOR) mixed matrix membranes were synthesized for direct methanol fuel cell (DMFC) use. For the structural and the morphological characterization, Scanning Electron Microscopy and Thermal Gravimetric Analysis methods were used. Zeolite distribution within the polymer matrix was found to be homogeneous. An impedance spectroscope was used to measure the proton conductivity. In order to obtain information about methanol permeation characteristics, swelling tests and a series of pervaporation experiments were carried out. 60–40wt% PVA–MOR membranes were found to give the optimum transport properties. Proton conductivity of these membranes was found to be slightly lower than that of Nafion117™ whereas their methanol permeability was at least two orders of magnitude lower than Nafion117™. DMFC performance of the PVA–MOR membranes was also measured. The inferior DMFC performance of PVA–MOR membranes was linked to drying in the fuel cell medium and the consequent proton conductivity loss. Their performance was improved by adding a dilute solution of sulfuric acid into the feed methanol solution. Future studies on the improvement of the proton conductivity of PVA–MOR membranes, especially via sulfonation of the polymer matrix, can overcome the low-performance problem associated with insufficient proton conductivity. [Copyright &y& Elsevier]

Direct methanol fuel cells (DMFCs) suffer from performance reduction due to mass transport losses incurred at high current regions. In this work, we report the use of activated carbon (AC), prepared from factory waste-tea, as cathode microporous layer in the membrane electrode assembly (MEA) of a DMFC, alleviating this mass transport effect. This biomass based AC framework, when tested under fuel cell operating conditions provided 0.25 V @ 300 mA cm −2 , enhancing cell performance by 33% over standard electrodes at 70 °C. During uninterrupted durability testing, this electrode displayed exceptional stability in mass transport dominated region, with loss of 15 mV day −1 , compared to 25 mV day −1 loss for the standard. Sample and electrode characterization measurements reveal that pore size distribution/particle size characteristics coupled with hydrophobic nature of the synthesized activated carbon, contributed to the performance improvement. [ABSTRACT FROM AUTHOR]

Graphite intercalation compounds (GIC) can be used as adsorbents for the removal of dissolved organic contaminants in water, and can be rapidly regenerated by electrochemical treatment. After electrochemical regeneration, the adsorption capacity of the GIC is often observed to increase compared to fresh adsorbent. This increase has been attributed to roughening of the surface as well as changes in surface chemistry. Specific surface areas of fresh and electrochemically treated GICs have been measured, and show no significant variation. Consequently, the electrochemical anodic oxidation process used to regenerate the material has been investigated, and these changes, specifically the transformation of the oxygen containing functional groups which is believed to give the GIC its surface chemistry properties, has been measured and studied. Analytical techniques including Scanning Electron Microscopy, Attenuated Total Reflectance Fourier Transform Infra-red spectroscopy, X-ray Photoelectron spectroscopy, Energy Dispersive X-ray spectroscopy and Boehm titrations were used to detect and estimate the relative amounts of functionalities such as carboxylic, quinone and lactonic functional groups. Results showed that fresh GICs have acidic quinone and carboxyl groups on the surface. These functional groups increase upon regeneration, however sustained regeneration leads to the formation of basic lactones which offset the relative amounts of the acidic groups. Acidic functional groups have been reported to increase adsorption, and consequently, there is an initial increase in adsorption due to surface acidic functionalities. Subsequent regeneration leads to the formation of basic functional groups which limit this enhanced adsorption. [ABSTRACT FROM AUTHOR]