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.

Automated summary

In this study, FL-SPES was investigated as a cathodic binder to improve fuel cell performance by increasing oxygen diffusion in the cathode. The gas permeability of FL-SPES was approximately three times higher than that of BP-SPES, leading to improved gas transfer and ultimately enhanced fuel cell performance.