CNT sheet as a cathodic functional interlayer in polymer electrolyte membrane fuel cells

Carbon nanotube (CNT) sheet was sandwiched between the cathodic GDBL and a bipolar plate of polymer electrolyte membrane fuel cells (PEMFCs). The CNT sheets were synthesized through the direct spinning method and investigated their morphological characteristics. The electrochemical performances of MEA with CNT interlayer were measured via polarizations, iR-free, and electrochemical impedance spectra (EIS) compared to the conventional MEA under elevating backpressure. The performance of the MEA with CNT interlayer at 1.0 barg was enhanced by 91.8% (364 mW cm−2 at 0.7 V), which was higher than the peak power density improvement of 13.0% (850 mW cm−2 at 0.48 V). We also identified that corresponding ohmic and charge-transfer resistances were reduced. Especially, the ohmic resistance was decreased by up to 42.2% with increasing operating pressure compared to the conventional MEA due to better hydration and interfacial contact. Notwithstanding that the performance was ameliorated with increased pressure, we found that the mass transport loss tends to become more sensitive at the high current density region, and thus optimum operating conditions were proposed. We concluded that the CNT sheet as a functional interlayer would be advantageous in improving the performance of commercialized PEMFCs. [Display omitted] •CNT sheet was sandwiched between cathodic GDBL and bipolar plate in PEMFCs.•CNT sheets were synthesized through the direct spinning method.•Power density at typical operating voltage enhanced 91.8% (364 mW cm−2 at 0.7 V).•Ohmic resistance was reduced by up to 42.2% with increasing operating pressure.