Preparation and applications of Nafion-functionalized multiwalled carbon nanotubes for proton exchange membrane fuel cells

Nafion-functionalized multiwalled carbon nanotubes (MWCNT-Nafion) are prepared through an ozone-mediated process. The chemical structure of MWCNT-Nafion is characterized by Raman spectroscopy, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Nafion chains covering on the outer surfaces of MWCNTs in MWCNT-Nafion is observed in high-resolution transmission electron micrographs. The Nafion fraction of MWCNT-Nafion is about 12 wt%. MWCNT-Nafion is effective to prepare Nafion/MWCNT-Nafion composite membranes for proton exchange membrane fuel cells. Compared to the pristine Nafion membrane, the composite membrane with a MWCNT-Nafion loading of 0.05 wt% (N/MN-0.05) exhibits an 1.5-fold increase of mechanical strength and a five-fold increase of proton conductivity. In single cell tests, the current density at 0.6 V and the maximum power density measured with the N/MN-0.05 composite membrane are 1556 mA cm−2 and 650 mW cm−2, respectively. Both of the values are 1.5-times the values measured with a pristine Nafion membrane.