Modified-Bio-Polymeric-Mixed-Matrix-Membrane Electrolytes for Direct Methanol Fuel Cells

J Solid State Electrochem

et al. 2011

Self Cite

Hybrid dual-network membranes comprising chitosan (CS)-polyvinyl alcohol (PVA) networks crosslinked with sulfosuccinic acid (SSA) and glutaraldehyde (GA) and modified with stabilized silicotungstic acid (SWA) are reported for their application in direct methanol fuel cells (DMFCs). Physico-chemical properties of these membranes are evaluated using thermo-gravimetric analysis and scanning electron microscopy in conjunction with their mechanical properties. Based on water sorption and proton conductivity measurements for the membranes, the optimum content of 10 wt.% SWA in the membrane is established. The methanol crossover for these membranes are studied by measuring the mass balance of methanol using density meter and are found to be lower compared to Nafion-117 membrane. The membrane-electrode assembly with 10 wt.% stabilized SWA-CS-PVA hybrid membrane with SSA and GA as crosslinking agent delivers a peak power density of 156 mW cm −2 at a load current density of 400 mA cm −2 and 88 mW cm −2 at a load current density of 300 mA cm −2 , respectively, in DMFC at 70°C.

Section: Proton Conductivity For the Membranesmentioning

confidence: 75%

Section: Sorption For the Membranesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Natural and synthetic solid polymer hybrid dual network membranes as electrolytes for direct methanol fuel cells

Meenakshi

J Solid State Electrochem

et al. 2011

Self Cite

“…Determination of methanol crossover using the density measurement method has already been reported elsewhere. 18,19 The permeated methanol from anode to cathode was measured by determining the methanol concentration based on the mass balance between the methanol supplied into the cell, methanol utilized for the electrochemical reaction, and unutilized methanol during the DMFC operation. The approach follows Faraday's concept, 38 where concentration of methanol varies with the load current-density with one mole of methanol being equivalent to 96,490 Coulombs.…”

Section: Methodsmentioning

confidence: 99%

“…[16][17][18] Biopolymeric mixed-matrix membrane electrolytes based on CS and gelatin have also been found to restrict the methanol crossover in DMFCs. 19 However, long-term stability of these membranes in relation to a commercially available Nafion-117 membrane is still a concern for their use in DMFCs. Membranes obtained by direct sulfonation of aromatic hydrocarbon polymers, such as poly ether ether ketone, polysulfone, or polyethersulfone, polybenzimidazoles, and polyphenylene oxide, have also been reported as alternative polymer-membrane-electrolytes for DMFCs.…”

mentioning

confidence: 99%

Modified-Pore-Filled-PVDF-Membrane Electrolytes for Direct Methanol Fuel Cells

Alwin

et al. 2011

J. Electrochem. Soc.

Self Cite

The polyvinylidene fluoride ͑PVDF͒ membrane is modified by the chemical etchant-route employing a sodium naphthalene charge-transfer complex followed by impregnation with Nafion ionomer or polyvinyl alcohol ͑PVA͒-polystyrene sulfonic acid ͑PSSA͒ polymeric blend solutions by a dip-coating technique to form pore-filled-membrane electrolytes for application in direct methanol fuel cells ͑DMFCs͒. The number of coatings on the surface-modified PVDF membrane is varied between 5 and 15 and is found to be optimum at 10 layers both for Nafion and PVA-PSSA impregnations for effective DMFC performance. Hydrophilicity of the modified-membrane electrolytes is studied by determining average contact angle and surface-wetting energy. Morphology of the membranes is analyzed by a cross-sectional scanning electron microscope. The modified PVDF membrane electrolytes are characterized for their water-methanol sorption in conjunction with their mechanical properties, proton conductivity, and DMFC performance. Air permeability for the modified membranes is studied by a capillary-flow porometer. Methanol crossover flux across modified-PVDF-membrane electrolytes is studied by measuring the mass balance of methanol using a density meter. DMFCs employing membrane electrode assemblies with the modified PVDF membranes exhibit a peak powerdensity of 83 mW/cm 2 with Nafion impregnation and 59 mW/cm 2 for PVA-PSSA impregnation, respectively. Among the membranes studied here, stabilities of modified-pore-filled PVDF-Nafion and PVDF-PVA-PSSA membranes with 10-layers coat are promising for application in DMFCs.Direct methanol fuel cells ͑DMFCs͒ have advanced substantially and are now almost universally referred to as the sixth-fuel-cell type. DMFCs are attracting commercial interest particularly because methanol has higher volumetric energy-density than hydrogen. 1,2 Besides, the promise of DMFCs to complement/substitute the existing batteries is being realized along with their potential as the future technology for mobile and portable-power applications. 3,4 Currently, perfluoro sulfonic acid membranes trade marked as Nafion are being used as polymer electrolyte in DMFCs. Nafion membranes have excellent ionic conductivity, long-term durability, and good mechanical stability. 5,6 However, Nafion membranes are expensive and suffer from high methanol crossover that not only results in wastage of the fuel but also vitiates the platinum catalyst on the cathode. 7 Accordingly, efforts are being expended to fabricate cost-effective alternative membranes to help reduce methanol crossover in DMFCs. 8,9 Polymer electrolyte blend membranes of polyvinyl alcohol ͑PVA͒ with different proton conducting agents, namely sulfosuccinic acid ͑SSA͒, polystyrene sulfonic acid ͑PSSA͒, and poly ͑sty-rene sulfonic acid-co-maleic anhyride͒, have been successfully employed in DMFCs. 10-12 Composite membranes with phosphotungstic acid-doped PVA, mordenite-incorporated PVA-PSSA, and heteropolyacid ͑HPA͒-incorporated chitosan ͑CS͒ are also found to restrict methanol crossover ...

Chitosan‐polyvinyl alcohol‐sulfonated polyethersulfone mixed‐matrix membranes as methanol‐barrier electrolytes for DMFCs

Meenakshi

J of Applied Polymer Sci

et al. 2011

Self Cite

Chitosan (CS)-polyvinyl alcohol (PVA) cross-linked with sulfosuccinic acid (SSA) and modified with sulfonated polyethersulfone (SPES) mixed-matrix membranes are reported for their application in direct methanol fuel cells (DMFCs). Polyethersulfone (PES) is sulfonated by chlorosulfonic acid and factors affecting the sulfonation reaction, such as time and temperature, are studied. The ion-exchange capacity, degree of sulfonation, sorption, and proton conductivity for the mixed-matrix membranes are investigated. The mixed-matrix membranes are also characterised for their mechanical and thermal properties. The methanol-crossover flux across the mixed-matrix membranes is studied by measuring the mass balance of methanol using the density meter. The methanol cross-over for these membranes is found to be about 33% lower in relation to Nafion-117 membrane. The DMFC employing CS-PVA-SPES mixed-matrix membrane with an optimum content of 25 wt % SPES delivers a peak power-density of 5.5 mW cm À2 at a load currentdensity of 25 mA cm À2 while operating at 70