Poly(vinylidene fluoride) (PVdF) and polyaniline (PAni) were partially sulfonated, using chlorosulfonic acid (CSA) as the sulfonating agent. The prepared partially sulfonated PVdF (SPVdF), having a degree of sulfonation ~22%, and the partially sulfonated PAni (SPAni), having a degree of sulfonation ~29%, were blended at constituent wt% ratios of SPVdF:SPAni = 95:5, 90:10, 85:15 and 80:20 in order to fabricate different blend membranes. These blend membranes exhibited extremely low methanol uptake and methanol permeability, as well as, high membrane selectivity ratios (especially at high methanol concentrations) The blend membranes also exhibited superior water uptake capacity, water swellability, ion-exchange capacity and proton conductivity, compared to the pristine PVdF and SPVdF membranes. The SPVdF:SPAni (80:20) blend membrane was found to produce the best results in terms of exhibiting the lowest methanol permeability values of 1.50×10-9 cm2s-1 (at 2 M methanol) and 6.30×10-9 cm2s-1 (at 8 M methanol), and the highest membrane selectivity values of 3.27×106 Sscm-3 (at 2 M methanol) and 7.78×105 Sscm-3 (at 8 M methanol). On the other hand, introduction of Nafion within the SPVdF/SPAni blend membrane, to form a ternary blend membrane (i.e. SPVdF:Nafion:SPAni = 50:30:20), resulted in much improved ion-exchange capacity and proton conductivity.

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Fulltext

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Polymer Journal

Severe crisis of energy that our planet is going to face in the near future demands rapid development of alternative energy harnessing and storing devices. Various alternative energy devices have been developed so far, including solar cells, batteries and fuel cells, in order to compete and replace the traditionally used fossil fuel based energy technologies. A very recent addition to the list of such devices is the unitized regenerative fuel cell (URFC), which can function as a dual, i.e., electrolyzer-cum-fuel cell, device. In remote areas, where utilization of conventionally used energy sources results in high expense, URFC can serve as the best energy option, due to its relatively low cost, high efficiency and light weight. URFC utilizes bifunctional electrodes, which function in a dual mode of water electrolysis and fuel cell. The prime focus of URFC research has been to develop various low cost and highly efficient catalysts and catalyst supports towards the fabrication of alternative bifunctional electrodes and to fabricate strong and efficient bipolar plates. The aim of this review is to highlight the main outcomes of these aspects of research on URFCs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Fuel Cells

Unitized Regenerative Fuel Cells: A Review on Developed Catalyst Systems and Bipolar Plates

Search for new catalyst (in place of traditionally used high cost Pt-Ru metal alloy) and catalyst supporting matrix (in place of conventionally used low efficient Vulcan carbon) for oxidation of methanol and application as anode catalyst system in direct methanol fuel cells (DMFCs) has been an active area of research for last several years. This work demonstrates utilization of comparatively less expensive and more abundant Ni metal catalyst, supported on polypyrrole (PPy) and partially sulfonated PPy (SPPy), as potential catalyst systems in place of the commercially used Pt-Ru/C catalyst system for oxidation of methanol. SPPy emerged as the best matrix for the Ni catalyst nanoparticles, in terms of catalyst deposition, dispersion, distribution and utilization. This combination generated a peak current density of 359 μAcm-2 at +0.579 V, as well as, a higher IF/IB ratio compared to the commercial Pt-Ru/C catalyst. In addition, Ni/SPPy produced a current density of 144.5 mAcm-2 (at +0.2 V potential) and a maximum power density of 28.9 mWcm-2 at 60 °C when utilized as an anode catalyst system in DMFC. The results, thus obtained, were far better than that exhibited by the commercial Pt-Ru/C, as well as, the Ni/PPy catalyst systems. © 2016 Elsevier B.V.

Materials Chemistry and Physics

Sulfonated polypyrrole matrix induced enhanced efficiency of Ni nanocatalyst for application as an anode material for DMFCs

Sulfonated poly(vinylidene fluoride-co-hexafluoro propylene) (SPVdF-co-HFP) and polyaniline (PAni) have shown promise as polymer electrolyte membrane (PEM) materials, especially in direct methanol fuel cells, by virtue of their significantly high ion-exchange capacity (IEC) and membrane selectivity ratio. It was intuited that utilization of PAni nanostructures, with high surface areas, in PEMs can result in further improvement of these attributes. With this objective, positively-charged PAni nanofibers (NFs) were synthesized. Interestingly, when these NFs were exposed to a negatively-charged amphiphile solution for different time extents and followed by washing with an organic solvent, PAni nanowhiskers (NWs) having lengths between 40-120 nm and diameters between 10-40 nm were formed. BET surface area exhibited an increase upon decrease in the aspect ratio of the NFs. Membranes were fabricated using SPVdF-co-HFP as the continuous phase and PAni granules, NFs or NWs as the dispersed phase. SPVdF-co-HFP/PAni NWs and SPVdF-co-HFP/PAni NFs membranes exhibited enhanced IECs, proton conductivities and selectivities compared to SPVdF-co-HFP/PAni granules membrane. However, comparisons between SPVdF-co-HFP/PAni NFs and SPVdF-co-HFP/PAni NWs membranes revealed that the extended conjugation available for the former versus the higher surface area of the latter played a crucial role in determining the uptake and transport properties of the membranes. © The Royal Society of Chemistry.

RSC Advances

Polyaniline nanowhiskers induced low methanol permeability and high membrane selectivity in partially sulfonated PVdF-co-HFP membranes

The development of potential anode catalysts and catalyst supporting matrices for application in direct methanol fuel cells (DMFCs) has been an active area of research for the last couple of decades. The conventionally used Pt catalyst suffers from (a) high cost, (b) limited abundance and (c) the catalyst poisoning effect induced by the in situ generated carbon monoxide. In this work, a comparatively less expensive and more abundant Ni metal catalyst [supported on Vulcan carbon, polyaniline (PAni) and partially sulfonated PAni (SPAni)] has been utilized as a potential alternative to the Pt metal catalyst for the oxidation of methanol. SPAni emerged as the best matrix for the deposited Ni catalyst nanoparticles. This combination generated a peak current density of 306 μA cm-2 at +0.57 V. In addition, the Ni/SPAni catalyst produced a higher I<inf>F</inf>/I<inf>B</inf> ratio compared to the commercial Pt-Ru/C catalyst. Furthermore, a current density of 135 mA cm-2 (at +0.2 V potential) and a maximum power density of 27 mW cm-2 were obtained at 60 °C upon utilizing Ni/SPAni as the anode catalyst for DMFCs. The results, thus obtained, were better than those obtained for the commercial Pt-Ru/C, as well as, the Ni/C and Ni/PAni catalysts. © The Royal Society of Chemistry 2015.

Journal of Materials Chemistry A

Nickel nanocatalysts supported on sulfonated polyaniline: Potential toward methanol oxidation and as anode materials for DMFCs

Partially sulfonated poly(vinylidene fluoride) (SPVdF) has been prepared by incorporation of sulfonic acid groups within poly(vinylidene fluoride), using chlorosulfonic acid as the sulfonating agent. The degree of sulfonation (DS) has been varied by modulating the duration of the sulfonation reaction. Blending of SPVdF (having DS = 36.78%) with Nafion at a constituent wt.% ratio of SPVdF:Nafion = 70:30 has resulted in the fabrication of polymer electrolyte membrane with superior properties compared to pristine Nafion-117 membrane. This particular blend composition exhibited a proton conductivity value of 3.6 × 10-2 S cm-1 (i.e. ∼12.5% increase over Nafion-117), a methanol permeability value of 6.81 × 10-7 cm2 s-1 at 6M methanol concentration (i.e. ∼99.31% decrease from Nafion-117) and a corresponding membrane selectivity value of 5.29 × 104 Ss cm-3 (i.e. an increase of approximately two-orders of magnitude over Nafion-117) at 20 °C. In addition, this blend composition has also exhibited (a) better heat stability at temperatures as high as 160 °C by virtue of it possessing higher glass transition temperature, (b) higher storage modulus, (c) higher stress relaxation at high angular frequency and (d) superior DMFC performance at high methanol feed concentration in presence of humidified, as well as, non-humidified air as the catholyte, compared to Nafion-117 membrane. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Partially Sulfonated Poly(vinylidene fluoride) Induced Enhancements of Properties and DMFC Performance of Nafion Electrolyte Membrane

The surface of Nafion 117 membrane was modified by dip-coating of a blend of polybenzimidazole (PBI) and partially sulfonated polyvinylidinefluoride-co-hfp (SPVDF-co-HFP) polymer without any significant change in the thickness of the membrane. The dip-coated membranes were characterized by FTIR spectroscopy, thermogravimetry and rheology; ion exchange capacity (IEC), proton conductivity and methanol permeability were also measured to find the suitability of these membranes in the direct methanol fuel cell (DMFC), especially keeping in view with a reduced methanol crossover and improved electrical efficiency. The IEC and proton conductivity of the membranes were observed to be lower than pristine Nafion 117 membrane. On the other hand, the methanol permeability of coated membranes was found to be very less than the pristine Nafion 117 membrane. Although, a very thin coat of the blends of PBI and SPVdF-co-HFP was applied on Nafion 117, the dynamic rheological studies indicated that the glass transition temperature of Nafion 117 shifted to a higher temperature, leading to higher stability of coated membranes at higher temperature in comparison to the stability of Nafion. The high thermal stability of the coated membranes compared to Nafion was also corroborated from the thermogravimetric analysis. All these results indicated that the coated Nafion 117 membrane could be electrically efficient at high temperature for DMFC applications. From the DMFC performance test, it was observed that the Nafion 117 membrane coated with 70:30 PBI and SPVDF-co-HFP showed the best electrical performance (39mW/cm2 at 0.2V) at the temperature of 90°C, whereas for pristine Nafion 117 membrane, the maximum electrical performance of the DMFC was observed to be 36mW/cm2 at the same voltage and at 60°C. © 2014 Elsevier B.V.

Journal of Membrane Science

Reduction of methanol crossover and improved electrical efficiency in direct methanol fuel cell by the formation of a thin layer on Nafion 117 membrane: Effect of dip-coating of a blend of sulphonated PVdF-co-HFP and PBI

pi-conjugated aromatic polymers (pi-CPs) are a class of high performance materials used in fabrication of a number of devices. Their use in direct methanol fuel cells (DMFCs) has resulted in improving the performance of this prospective alternative energy harnessing device. This review focuses on these aspects of pi-CPs, from fabrication techniques to structure-property relationships and finally performance evaluation and comparison with other potential candidates. Along with an overview of the step-by-step progress that has been made in the last two decades, this review consists of a separate section dedicated to the advancements made in the last five years. This period has seen considerable progress in terms of preparation techniques, such as fabrication of layer-by-layer assembly and core-shell assembly; materials used, such as variety of dopants for pi-CPs and sulfonated polymers in case of PEMs and pi-CP composites with carbon nanotubes and graphenes in case of catalyst supporting matrices; and surface morphology, such as use of nanofibers, nanotubes, and nanowires. In addition, different polymerization strategies and solubility aspects of pi-CPs have also been discussed. All these modifications have resulted in yielding high power and current densities, mass specific activity, stability, durability, and judicious utilization of costly materials, like Pt and Nafion.

Polymer Reviews

Synthesis, Preparation, and Performance of Blends and Composites of pi-Conjugated Polymers and their Copolymers in DMFCs

Fuel cells (FCs) have evolved as a potential alternative energy harnessing device, with direct methanol fuel cell (DMFC) as one of the front-runners. Although it has achieved significant progress, and is currently getting available in the commercial market; however, from a broader perspective, DMFCs, like most other devices, suffer from certain critical drawbacks. This, in turn, demands considerable progress to be made in order to realize ultimate commercialization, i.e., cheap, reliable, durable, and portable DMFCs with easily accessible fuel. In this respect, one important area of real concern is the DMFC electrodes, consisting of catalysts and catalyst-supporting matrices. Sluggish reaction rates and use of highly expensive and scarce catalysts are two critical drawbacks. Conducting polymers (CPs) have found extensive use in the fabrication of these matrices and have resulted in better dispersion, distribution and anchoring of catalysts, which is important to enhance their reaction efficiencies. This review attempts to summarize the potential contributions of CPs, their critical roles, and possible future trends toward fabricating catalyst-supporting matrices in DMFCs.

Journal	Polymer Journal
Publisher	Nature Publishing Group
ISSN	0032-3896