Sulfonated poly(arylene ether nitrile)-based composite membranes enhanced with Ca2+ bridged carbon nanotube-graphene oxide networks

As the core component of proton exchange membrane fuel cell, proton exchange membranes (PEM) have attracted much attention of researchers. To trade-off the proton conduction, dimensional stability and anti-oxidation ability, graphene oxide (GO) and acidized multi-walled carbon nanotubes (MWCNT) using calcium ion as coordination bridge (GO-Ca2+-MWCNT) was synthesized, and then incorporating into sulfonated poly(arylene ether nitrile) (SPEN) to fabricate SPEN/GO-Ca2+-MWCNT organic-inorganic composite membranes by solution-casting method and explore the influence of varying loading on performances as PEM. It was found that the proton conductivity of the composite membranes was higher than that of SPEN, while maintaining better dimensional stability, excellent anti-oxidation ability and good mechanical properties. All of these were attributed to the formation of three-dimensional structure between GO and MWCNT bridged by Ca2+. Particularly, the SPEN/GO-Ca2+-MWCNT-1 composite membrane exhibited excellent tensile strength of 71.45 MPa, better thermal stability as well as high proton conductivity (0.054 S/cm at 30 ℃, and 0.193 S/cm at 90 ℃), above 10-2 S/cm, satisfying the requirement of fuel cells. All in all, the results indicate that the filler with three-dimensional network structure can effectively improve the performances of SPEN, and the prepared composite membranes show potential applications in many fields.

Characterization of a Sulfonated Poly(Ionic Liquid) Block Copolymer as an Ionomer for Proton Exchange Membrane Fuel Cells using Rotating Disk Electrode

Ionic liquid (IL) additives to both traditional and advanced oxygen reduction reaction (ORR) electrocatalysts have yielded remarkable improvements in catalyst performance and durability. However, incorporating ILs or IL-modified catalysts into the electrodes of a proton exchange membrane fuel cell (PEMFC) membrane electrode assembly (MEA) has proven to be challenging. Sulfonated poly(ionic liquid) block copolymers (S-PILBCP) present an opportunity to incorporate IL functionality directly into the ionomer, orthogonal to protonic conductivity. Here, we use a rotating disc electrode (RDE) to characterize the interface between a S-PILBCP and Pt catalyst in comparison to Nafion. Catalyst thin films prepared with S-PILBCP show an 80% improvement in the ORR activity over those containing Nafion. Thin films of S-PILBCP also show a significantly reduced degree of poisoning sulfonate adsorption on a Pt(111) surface in comparison to Nafion. These half-cell results provide useful insights that help to highlight the source of the impact of the S-PILBCP on PEMFC MEA performance.