Direct Methanol Fuel Cell Performance of Disulfonated Poly(arylene ether benzonitrile) Copolymers

Abstract

This paper reports the performance of direct methanol fuel cells ͑DMFCs͒ using novel disulfonated poly͑arylene ether benzoni-trile͒ copolymers derived from hexafluoro-isopropylidene diphenol ͑6F͒, 2,6-dichlorobenzonitrile, and 3,3Ј-disulfonated 4,4Ј-dichloro diphenyl sulfone ͑SDCDPS͒. The membrane electrode assembly ͑MEA͒ which employed the sulfonated copolymer with 35 mol % of disulfonated comonomer as the proton exchange membrane had approximately 2-fold lower methanol crossover and slightly higher ͑about 10%͒ cell resistance than the MEA using the perfluorosulfonic acid Nafion membrane, resulting in an approximately 50% improvement in selectivity, regardless of membrane thickness. Accordingly, this MEA outperformed the Nafion MEA control in a DMFC single-cell test. For example, 200 mA/cm 2 was obtained ͑compared with 150 mA/cm 2 for the Nafion MEA͒ at 0.5 V at a temperature of 80°C and ambient air pressure. Similar experiments performed with nonfluorinecontaining biphenol-based sulfonated poly͑arylene ether sulfone͒ copolymers ͑BPSH͒ indicated that the compatibility of the polymer electrolyte with the electrodes likely has a critical role in initial DMFC performance.

Surface orientation of hydrophilic groups in sulfonated poly(ether ether ketone) membranes

“…Similar to our finding, Kim et al investigated surface fluorine enrichment in the 6FCN-35 membranes [52], i.e., disulfonated poly(arylene ether benzonitrile) copolymers containing hexafluoroisopropylidene diphenol, whose molar ratio of unsulfonated benzonitrile to the disulfonated sulfone monomer was 65:35. They also found that surface fluorine, lower surface energy group, was enriched on the air-contacting surface to about 38%, doubling the 17% of fluorine content of the bulk membrane.…”

“…The glass-contact surface was found to have close to unchanged fluorine content about 15%. The differences of fluorine atomic concentration on different sides of a membrane were attributed to the low surface free energy of the hexafluoroisopropylidene moiety, which provided a thermodynamic driving force for the selfassembly at the air-polymer interface, leading to fluorine hydrophobic groups enrichment, on the air-contacting membrane surface [52]. In this study the information about the membrane surface within less than 1 µm was investigated using ATR-FTIR (Fig.…”

Interpretation of direct methanol fuel cell electrolyte properties using non-traditional length-scale parameters

“…Although this is outside the scope of this paper, there are a few references in this regard [60,61]. Improved DMFC performance is then anticipated with a well-designed DMFC PEMs [62,63].…”

Preparation and DMFC performance of a sulfophenylated poly(arylene ether ketone) polymer electrolyte membrane

“…DMFC MEA fabrication and fuel cell operating conditions were conducted according to a reported procedure [3,5]. The anode ink composition was 86 wt% 1:1 platinum-ruthenium (Johnson Matthey) and 14 wt% Nafion ® , and the cathode ink composition was 90 wt% platinum black (Johnson Matthey) and 10 wt% Nafion ® .…”

“…Known for their outstanding chemical, mechanical and oxidative stability and high proton conductivity, perfluorinated sulfonic acid polymers (such as Nafion ® ) exhibit excellent electrochemical performance as polymer electrolyte membranes (PEMs). To date, only a few PEMs have been reported to possess improved single cell performance over commercial Nafion ® -type PEMs [3][4][5][6][7]. As an example, the PEMs based on stretched recast Nafion ® were claimed to have better performance than commercial Nafion ® in DMFCs [6,7].…”