Abstract
Poor mechanical property is a critical problem for phosphoric acid-doped high-temperature proton exchange membranes (HT-PEMs). In order to address this concern, in this work, a 3D network structural poly (aryl ether ketone)-polybenzimidazole (PAEK-cr-PBI) polymer electrolyte membrane was successfully synthesized through crosslinking reaction between poly (aryl ether ketone) with the pendant carboxyl group (PAEK-COOH) and amino-terminated polybenzimidazole (PBI-4NH2). PAEK-COOH with a poly (aryl ether ketone) backbone endows superior thermal, mechanical, and chemical stability, while PBI-4NH2 serves as both a proton conductor and a crosslinker with basic imidazole groups to absorb phosphoric acid. Moreover, the composite membrane of PAEK-cr-PBI blended with linear PBI (PAEK-cr-PBI@PBI) was also prepared. Both membranes with a proper phosphoric acid (PA) uptake exhibit an excellent proton conductivity of around 50 mS cm-1 at 170°C, which is comparable to that of the well-documented PA-doped PBI membrane. Furthermore, the PA-doped PAEK-cr-PBI membrane shows superior mechanical properties of 17 MPa compared with common PA-doped PBI. Based upon these encouraging results, the as-synthesized PAEK-cr-PBI gives a highly practical promise for its application in high-temperature proton exchange membrane fuel cells (HT-PEMFCs).
Highlights
Proton exchange membrane fuel cells (PEMFCs) have drawn much attention as clean power generation devices due to their many attractive features, such as high efficiency, high power density, and environmental friendliness for potential application as power sources in stationary transportation and portable devices [1,2,3,4,5]
Among all the types of HT-Proton exchange membranes (PEMs), phosphoric aciddoped polybenzimidazole (PA-PBI) membranes have been considered to be the most promising candidates for a hightemperature proton exchange membrane owing to its good chemical and thermal stability and excellent proton conductivity under anhydrous conditions at high temperature [9,10,11,12]
The synthesis route of PAEK-cr-PBI is shown in Scheme 1(c), and the PAEK-cr-PBI membrane was fabricated by a solution casting method, as shown in Scheme 2
Summary
Proton exchange membrane fuel cells (PEMFCs) have drawn much attention as clean power generation devices due to their many attractive features, such as high efficiency, high power density, and environmental friendliness for potential application as power sources in stationary transportation and portable devices [1,2,3,4,5]. Other macromolecular crosslinkers such as poly (vinyl benzyl chloride) [30] and bromomethylated poly (aryl ether ketone) [31] have been adopted to prepare crosslinked PBI membranes Most of these methods are based on the sacrifice of N-H sites on the imidazole ring of the PBI main chain, which impedes the absorption of phosphoric acid and proton transport [32]. In order to better evaluate the performance of the assynthesized PAEK-cr-PBI and PAEK-cr-PBI@PBI membranes, we compared the well-documented PBI membrane with it The properties of these membranes, including their solubility in common solvent, morphology analysis, thermal stability, oxidative stability, proton conductivity, and mechanical strength, were studied and compared
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