Novel functionalized carbon nanotubes as cross-links reinforced vinyl ester/nanocomposite bipolar plates for polymer electrolyte membrane fuel cells

In this study, the novel functionalized multi-walled carbon nanotubes (MWCNTs) are used as cross-links between MWCNTs–vinyl ester interfaces to achieve homogeneous dispersion and strong interfacial bonding for developing fully integrated MWCNTs–vinyl ester nanocomposite bipolar plates. POAMA (i.e. poly(oxyalkylene)-amines (POA) bearing maleic anhydride (MA)) are grafted onto the MWCNTs by amidization reaction, forming MWCNTs-POAMA. In the MWCNTs-POAMA/vinyl ester nanocomposites, MWCNT-POAMAs react with vinyl ester and become part of the cross-linked structure, rather than just a separate component. It is found that the MWCNTs-POAMA exhibited better dispersion in the vinyl ester matrix than those of pristine MWCNTs. Moreover, the results demonstrate that the mechanical and electrical properties of the vinyl ester nanocomposite bipolar plate are improved dramatically. The ultimate flexural strength, unnotched impact strength, in-plane electrical conductivity and contact resistance of the MWCNTs-POAMA/vinyl ester nanocomposite bipolar plate are increased by 45%, 90%, 315% and 28%, respectively. In addition, the maximum current and power densities of the single fuel cell test using the MWCNTs-POAMA/vinyl ester nanocomposite bipolar plates is enhanced from 1.03 to 1.23 A cm−2 and from 0.366 to 0.518 W cm−2, respectively, which suggested that a higher electron transfer ability for polymer electrolyte membrane fuel cell applications can be achieved.