Enhanced proton conductivity of Nafion-azolebisphosphonate membranes for PEM fuel cells

• Published in: New journal of chemistry 2019-09, Vol.43 (38), p.15249-15257
• Main Authors: Teixeira, Fátima C, de Sá, Ana I, Teixeira, António P. S, Rangel, C. M
• Format: Article
• Language: English
• Subjects: Alternative energy sources; Alternative fuels; Conductivity; Electrochemical impedance spectroscopy; Energy technology; Fuel cells; Membranes; Phosphonic acids; Proton conduction; Proton exchange membrane fuel cells; Relative humidity
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c9nj03405f

Fuel cells are among the cleaner alternatives of sustainable energy technologies, where their proton exchange membranes continue to be a key component with many challenges and opportunities ahead. In this study, different indazole- and benzotriazolebisphosphonic acids were prepared and incorporated into new Nafion-doped membranes up to a 5 wt% loading. The new membranes were characterised, and their proton conductivities were evaluated using electrochemical impedance spectroscopy. Membranes with a 1 wt% loading showed better proton conductivities than Nafion N-115 at all temperature and under relative humidity conditions studied. In these conditions, the best value was observed for the membrane doped with [hydroxy(1 H -indazol-3-yl)methanediyl]bis(phosphonic acid) (BP2), with a proton conductivity of 98 mS cm −1 . Activation energy ( E a ) values suggests that both Grotthuss and vehicular mechanisms are involved in the proton conduction across the membrane. Azolebisphosphonates were prepared and used as dopants to obtain new Nafion doped membranes, which exhibited higher proton conductivities than that of Nafion.