A flexible all-inorganic fuel cell membrane with conductivity above Nafion, and durable operation at 150°C

The search for fuel cell membranes has focused on carbon backbone polymers, among which Nafion seems to best survive the most severe of the degradation mechanisms - attack by peroxide radicals. Less attention has been given to inorganic membranes because of their generally inflexible nature and lower conductivity, though some SiO2-Nafion composites have shown improved properties. Nation dominates, despite needing hydration, which then restricts operation to below 100 degrees C (so CO poisoning problems persist). Described herein is a low cost, flexible, and all-inorganic fiberglass reinforced gel membrane with conductivity exceeding that of Nafion at any temperature above 60 degrees C. Using Teflon fuel cells, maximum currents > 1 Acm(-2) and OCV of 1.03 V at 150 degrees C are demonstrated. No detectable loss of cell potential was observed over 24 h during 50 mAcm(-2) constant current operation at 120 degrees C while, at 150 degrees C and maximum power, the degradation rate is intermediate among other high conductivity H3PO4-PBI type membranes. The structure of the membrane is deduced, mainly from Si-29 solid state-NMR. The -115 ppm resonance, which is extreme for Q(4) Si(O) structures, identifies a zeolite-like SiO2 network, which is floppy. P-31 and H-1 NMR establish nano-permeating H3PO4 as the source of the exceptional conductivity. (C) 2015 Elsevier B.V. All rights reserved.