Synthesis and Solid-State NMR Studies of Proton-Conducting Mesoporous Niobium Oxide Polymer Composites with Nafion-Like Thermal Durability

Proton conductivity and thermal durability studies were performed on a series of mesoporous Nb2O5 composites with naphthalene sulfonate formaldehyde resin polymerized within the pores. The proximity of the sulfonate groups of the polymer to the walls of the oxide mesostructure was deliberately tailored to ensure superior dehydration resistance crucial to proton conductivity. Initially characterized by nitrogen adsorption, XRD, TGA and STEM, subsequent study using impedance spectroscopy over a temperature range of 20–150 °C established their proton conductivity performance. The most promising sample displayed a conductivity of 21.77 mS cm−1 at 80 °C surpassing the literature value for Nafion 117 (8 mS cm−1) as measured in our labs using the same setup. Subsequent thermal durability tests demonstrated that this composite maintains superior conductivity to Nafion 117 at 80 °C for the length of the study (24 h). These observations were rationalized by in depth solid-state NMR studies.