1 Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, SDU2 Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU3 NanoMaterials Group, Department of Applied Physics, School of Science, Aalto University, Puumiehenkuja 2, 02150 Espoo, Finland4 New Materials Department, IK4-CIDETEC, Paseo Miramón 196, E-20009 Donostia-San Sebastián, Spain5 Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, SDU6 Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU
The interaction between high surface area nano-carbon catalyst supports for proton exchange membrane fuel cells (PEMFCs) and perfluorinated sulfonic acid (Nafion®) ionomer was studied 19 fluorine nuclear magnetic resonance spectroscopy (19F-NMR). The method was developed and improved for more efficient, user-friendly and systematic studies based on our earlier experience. In this work, multi-walled carbon nanotubes (MWCNTs) from Showa Denko® and the corresponding acid modified products were explored. The adsorption at low concentration was found to follow a Langmuir isotherm. Adsorption equilibrium constant (Keq.) and maximum surface coverage (Γmax) were determined based on the model. In general, the ionomer showed stronger adsorption for MWCNTs (Keq. = 21 − 377 depending on treatment) comparing to Vulcan (Keq. = 18), and slightly lower monolayer coverage. The interaction was found to be strongly affected by surface composition, morphology, porosity and oxygen containing functional groups, which are varied with purification and functionalization treatments. The modification of the surface properties was also studied with HR-TEM, BET, porosity measurement, EDXS, XPS, Raman and TG. The results will contribute to optimize electrode preparation with novel nano-carbon catalyst supports and durable catalyst for low temperature (LT) PEMFCs.