One-step fabrication and characterization of reinforced microcomposite membranes for polymer electrolyte membrane fuel cells

Novel Side-Chain Type Sulfonated Poly(phenylquinoxaline) Proton Exchange Membranes for Direct Methanol Fuel Cells

Side-chain type sulfonated poly(phenylquinoxaline) (SPPQ)-based proton exchange membranes (PEMs) with different ionic exchange capacity (IEC) were successfully synthesized by copolymerization from 4,4'-bis (2-diphenyletherethylenedione) diphenyl ether, 4,4'-bis (2-phenylethylenedione) diphenyl ether and 3,3',4,4'-tetraaminobiphenyl, and post-sulfonation process. The sulfonic acid groups were precisely grafted onto the p-position of phenoxy groups in the side chain of PPQ after the convenient condition of the post-sulfonation process, which was confirmed by ¹H NMR spectra and FTIR. The sulfonic acid groups of side-chain type SPPQ degraded at around 325 °C, and their maximum stress was higher than 47 MPa, indicating great thermal and mechanical stability. The water uptake increased with the increasing IEC and temperature. The size change in their plane direction was shown to be lower than 6%, indicating the stability of membrane electrode assembly. The SPPQ PEMs displayed higher proton conductivity than that of main chain. In the single cell test, the maximum power density of side-chain type SPPQ-5 was 63.8 mW cm^-2 at 20 wt% methanol solution and O₂ at 60 °C, which is largely higher than 18.4 mW cm^-2 of NR212 under the same conditions. The SPPQ PEMs showed high performance (62.8 mW cm^-2) even when the methanol concentration was as high as 30 wt%.

Fuel cell performance improvement via the steric effect of a hydrocarbon-based binder for cathode in proton exchange membrane fuel cells

In this study, a sulfonated poly(ether sulfone) having cardo-type fluorenyl groups (FL-SPES) was investigated as a cathodic binder to improve fuel cell performance via increased the oxygen diffusion in the cathode. The maximum power density achieved by using the membrane electrode assembly (MEA) prepared with FL-SPES with a low ion exchange capacity (IEC) of 1.31 meq g^-1 was 520 mW cm^-2, which is more than twice as high as that of BP-SPES (210 mW cm^-2) having typical biphenyl groups with a similar IEC. At high IEC of 1.55 meq g^-1, the power density obtained by using BP-SPES was improved to 454 mW cm^-2 but remained lower than that of FL-SPES. In addition, although the IEC, swelling degree, and specific resistance were similar to each other, the gas permeability of FL-SPES was improved by approximately three times compared to that of BP-SPES. The steric structure of cardo-type FL-SPES increased the free volume between the polymer backbones, leading to an increase in gas transfer. Consequently, oxygen diffusion was promoted at the cathode, resulting in improved fuel cell performance.

Waterproof-breathable PTFE nano- and Microfiber Membrane as High Efficiency PM2.5 Filter

This study shows the feasibility of using electrospinning technique to prepare polytetrafluoroethylene/poly (vinyl alcohol) (PTFE/PVA) nanofibers on PTFE microfiber membrane as substrate. Then, PVA in the fiber membrane was removed by thermal treatment at about 350 °C. Compared to PTFE microfiber substrates, the composite PTFE fiber membranes (CPFMs) have improved filtration efficiency by 70% and water contact angle by 23°. Experimental test data showed that the water contact angle of the sample increased from about 107° to 130°, the filtration efficiency of PM2.5 increased from 44.778% to 98.905%, and the filtration efficiency of PM7.25 increased from 66.655% to 100% due to the electrospun PTFE nanofiber layer. This work demonstrates the potential of CPFMs as a filter for the production of indoor or outdoor dust removal and industrially relevant gas filtration.