Abstract
Polymer membranes, having improved conductivity with enhanced thermal and chemical stability, are desirable for proton exchange membranes fuel cell application. Hence, poly(benzophenone)s membranes (SI-PBP) containing super gas-phase acidic sulfonyl imide groups have been prepared from 2,5-dichlorobenzophenone (DCBP) monomer by C-C coupling polymerization using Ni (0) catalyst. The entirely aromatic C-C coupled polymer backbones of the SI-PBP membranes provide exceptional dimensional stability with rational ion exchange capacity (IEC) from 1.85 to 2.30 mS/cm. The as-synthesized SI-PBP membranes provide enhanced proton conductivity (107.07 mS/cm) compared to Nafion 211® (104.5 mS/cm). The notable thermal and chemical stability of the SI-PBP membranes have been assessed by the thermogravimetric analysis (TGA) and Fenton’s test, respectively. The well distinct surface morphology of the SI-PBP membranes has been confirmed by the atomic force microscopy (AFM). These results of SI-PBP membranes comply with all the requirements for fuel cell applications.
Highlights
Eco-friendly proton exchange membranes fuel cells (PEMFC) are regarded as an effective substitute for fossil fuels [1–6]
The 2,5-dichlorobenzophenone (DCBP) monomer was synthesized from 2,5-dichlorotoluene followed by Friedel-Craft acylation with benzene (Scheme S1). 1 H-NMR (Nuclear Magnetic Resonance) was used to confirm the structure of the DCBP monomer (Figure S1)
The polymer membranes based on sulfonamide poly(benzophenone)s (SI-Poly(Benzophenone) Polymers (PBP)) were synthesized by Ni (0) catalyzed C-C coupling polymerization of 2,5-dichloro-benzophenone
Summary
Eco-friendly proton exchange membranes fuel cells (PEMFC) are regarded as an effective substitute for fossil fuels [1–6]. The pre-sulfonation process (i.e., using sulfonated monomers) is found to be more convenient than post-sulfonation of the membranes but sometimes it can be very difficult to achieve the high molecular weight polymers from primarily sulfonated monomers [12–16]. Most of these sulfonated polymers show oxidative and hydrolytic stabilities either for their ether linkage-based polymer backbones nor for the attachment of sulfonic acid groups directly to the main polymer chain as they are susceptible to nucleophilic attacks [17,18]. The lower acidity of the sulfonic acid groups is accountable for the poor conductivity in the fuel cells
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