Investigations into the ex situ methanol, ethanol and ethylene glycol permeabilities of alkaline polymer electrolyte membranes

摘要

Alkaline anion-exchange membranes (AAEMs) are being developed for metal-cation-free solid alkaline fuel cells. Reduced solvent uptakes were observed after immersion in methanol, ethanol and ethylene glycol relative to a Nafion~®-115 proton-exchange membrane (PEM); this translated directly into lower alcohol permeabilities. Alkaline polymer electrolytes showed lowered degrees of swelling (membrane thickness), when immersed in methanol and ethanol, relative to Naflon-115. The open circuit voltages, Vocv, of the corresponding direct alcohol fuel cells were superior to acid equivalents with membranes of identical fully hydrated thicknessess; this is indicative of a combination of reduced alcohol permeabilities and changed electrokinetics on PtRu anode catalysts at high pH. Vocv values for the AAEM-DAFCs were higher with ethanol than with methanol (consequent on lower permeability to ethanol), but were lower with ethylene glycol. Promisingly, and contrary to Nation equivalents, peak power densities were not reduced when C_2 alcohols (C-C bond containing) replaced methanol.