One-step functionalization of carbon nanotubes by free-radical modification for the preparation of nanocomposite bipolar plates in polymer electrolyte membrane fuel cells

This study presents a novel one-step preparation of functionalized multi-walled carbon nanotubes (MWCNTs) by free-radical modification. MA-POA, i.e. maleic anhydride ( MA) grafted on molecular weight 400 and 2000 poly(oxyalkylene)amines (POA400 and POA2000), was attached onto the MWCNTs, forming MWCNTs/MA-POA400 and MWCNTs/MA-POA2000. The functionalized MWCNTs, especially MWCNTs/MA-POA2000, exhibited higher solubility than the pristine MWCNTs in organic solvents and were well dispersion in a vinyl ester matrix. Furthermore, this study also investigated mechanical, electrical and single fuel cell properties of functionalized MWCNT nanocomposite bipolar plates for use in polymer electrolyte membrane fuel cells (PEMFCs). The flexural strength of the nanocomposite bipolar plates containing 2 wt% MWCNTs/MA-POA2000 was increased from 28 MPa to 48.33MPa. In addition, the in-plane and through-plane electrical conductivities and half-cell resistance of the nanocomposite bipolar plates were 780%, 168% and 253%, respectivel,y higher than those of the original composite bipolar plates with the addition of only a small quantity ( 1 wt%) of MWCNTs/MA-POA2000. The maximum current density and power density of the single cell tests of the nanocomposite bipolar plate with 1 wt% MWCNTs/MA-POA2000 were enhanced from 1.03 to 1.32 A cm(-2) and from 0.392 to 0.580 W cm(-2), respectively. The overall performance confirms the MWCNTs/MA-POA2000 nanocomposite bipolar plates prepared in this study are suitable for PEMFC application.