Highly Effective Proton-Conduction Matrix-Mixed Membrane Derived from an -SO 3 H Functionalized Polyamide.

Developing a low-cost and effective proton-conductive electrolyte to meet the requirements of the large-scale manufacturing of proton exchange membrane (PEM) fuel cells is of great significance in progressing towards the upcoming "hydrogen economy" society. Herein, utilizing the one-pot acylation polymeric combination of acyl chloride and amine precursors, a polyamide with in-built -SO 3 H moieties ( PA-PhSO 3 H ) was facilely synthesized. Characterization shows that it possesses a porous feature and a high stability at the practical operating conditions of PEM fuel cells. Investigations of electrochemical impedance spectroscopy (EIS) measurements revealed that the fabricated PA-PhSO 3 H displays a proton conductivity of up to 8.85 × 10 -2 S·cm -1 at 353 K under 98% relative humidity (RH), which is more than two orders of magnitude higher than that of its -SO 3 H-free analogue, PA-Ph (6.30 × 10 -4 S·cm -1 ), under the same conditions. Therefore, matrix-mixed membranes were fabricated by mixing with polyacrylonitrile (PAN) in different ratios, and the EIS analyses revealed that its proton conductivity can reach up to 4.90 × 10 -2 S·cm -1 at 353 K and a 98% relative humidity (RH) when the weight ratio of PA-PhSO 3 H :PAN is 3:1 (labeled as PA-PhSO 3 H-PAN (3:1) ), the value of which is even comparable with those of commercial-available electrolytes being used in PEM fuel cells. Additionally, continuous tests showed that PA-PhSO 3 H-PAN (3:1) possesses a long-life reusability. This work demonstrates, using the simple acylation reaction with the sulfonated module as precursor, that low-cost and highly effective proton-conductive electrolytes for PEM fuel cells can be facilely achieved.