Synthesis of Sulfonic Acid-Containing Polybenzoxazine for Proton Exchange Membrane in Direct Methanol Fuel Cells

Abstract

A novel sulfonic acid-containing benzoxazine monomer, 3-[4-(4-(6-sulfo-3,4-dihydro-2H-1,3-benzoxazine-3yl)benzyl)phenyl]-3,4-dihydro-2H-1,3-benzoxazine-6-sulfonic acid (abbreviated as SHS-ddm), was synthesized via Mannich reaction and acidizing reaction using sodium 4-hydroxybenzenesulfonate, 4,4′-diaminodiphenylmethane, and paraformaldehyde as raw materials. The structure of SHS-ddm was characterized by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance ( 1 H NMR) spectroscopy, and electrospray ionization mass spectrometry (ESI−MS). The crosslinked sulfonic acid-containing polybenzoxazine [poly(SHS-ddm)] membrane was prepared through high temperature solutioncasting method. Membrane properties including proton conductivity, methanol permeability, mechanical property, hydrolytic and oxidative stabilities were evaluated in detail. Our results showed that poly(SHS-ddm) membrane exhibited a high proton conductivity of 0.154 S cm −1 at 80 °C and a very low methanol permeability of 5.8 × 10 −8 cm 2 s −1 . The calculated selectivity parameter was 2.655 × 10 6 S s cm −3 , which was much higher than that of Nafion 117 (8.081 × 10 4 S s cm −3 ). Employing this membrane in the membrane-electrode assembly (MEA), high methanol concentration up to 7 M was used. The cell exhibited a stable open circuit voltage (V OC ) of 0.76 V and a maximum power density of 66.5 mW cm −2 . Accordingly, only relatively low voltage drop of 1.415 mV h −1 was observed after a continuous operation for 12 h. Overall, this novel polybenzoxazine exhibited special potential for proton exchange membrane with low methanol permeability and low cost in direct methanol fuel cells.

Preparation and characterization of sulfonated poly(aryl ether ketone)s containing 3,5-diphenyl phthalazinone moieties for proton exchange membrane

“…However, there remain signicant limitations to current commercial materials, such as high methanol crossover rate and low operational temperature (methanol fuel cell, <80 C). [5][6][7] To overcome these problems, more novel sulfonated aromatic polymers have been synthesized and evaluated as alternatives to Naon. [8][9][10][11][12] Based on previous reports, these substituted aromatic polymers can be roughly classied into two major categories.…”

Poly(arlyene ether sulfone) based semi-interpenetrating polymer network membranes containing cross-linked poly(vinyl phosphonic acid) chains for fuel cell applications at high temperature and low humidity conditions

“…Although the initial cell voltages in the low current density region of the MEA from B15 are smaller than those from the recastNafion ® membrane, larger cell voltage values in the ohmic resistance and high current density regions, in the range of about 100e550 mA cm À2 , were observed from the MEA from B15 membrane. The initial voltage drop of polarization curves has been ascribed to the retardation of the oxygen reduction reaction (in the electrochemical activation process) at the cathode [2,67,68]. Since the same electrodes were used for the cell performance measurements of the two MEAs from B15 and recast-Nafion ® membranes, the initial cell voltage drops should be attributed to the difference of the interfacial resistance at the membrane-electrode interfaces of the two MEAs [69].…”

Fabrication and characterization of sulfonated polybenzimidazole/sulfonated imidized graphene oxide hybrid membranes for high temperature proton exchange membrane fuel cells

“…5 Operating fuel cells at high temperature (120-200 C) is advantageous because of their high carbon monoxide tolerance, high amount of reusable heat energy, low dependencies on cooling systems and high feasibility in hydrogen feeding systems 6 and faster oxygen reduction rate. [9][10][11] These limitations in the commercial perfluorinated membranes started a scientific breakthrough to synthesize suitable candidates for polymer electrolyte membranes of high temperature applications in the last decades. 7,8 At present, Nafion (the commercial perfluorinated membrane) is readily recognized state-of-the-art standard for polymer electrolyte membranes of PEMFCs.…”