A 1H NMR pulse gradient spin-echo (PGSE) study of the mass transport of dimethyl oxalate and ethylene glycol: New fuels for the DOFC

S. Suarez, S. H. Chung, S. Greenbaum, S. Bajue, E. Peled, T. Duvdevani

Research output: Contribution to journalArticlepeer-review

Abstract

Direct oxidation fuel cell (DOFC) based on proton conducting membranes (PCM's) represents a promising energy technology, with the vast majority of efforts devoted to methanol as the fuel. The most commonly used PCM is Nafion. However, because of high production cost, high fuel crossover, and sensitivity to metal-ion impurities, alternative materials are being developed. Methanol presents several limitations including low boiling point (∼65 °C), and reduced cell efficiency due to fuel crossover. We present here a measure of the mass transport represented by the self-diffusion coefficients (D) of methanol, and two alternative fuels - ethylene glycol (EG) and dimethyl oxalate (DMO) in new low-cost nanoporous (NP) PCM's. The NP-PCM's are based on commercial poly(vinylidene fluoride), with variable pore size determined by the addition of nanoscale SiO2 or TiO2 particles. Proton NMR pulsed gradient spin-echo (PGSE) self-diffusion measurements were conducted on aqueous solutions of 2 M fuel in 3 M H2SO4 and also on five NP-PCM equilibrated in the aqueous solutions over the temperature range of 30-90 °C. Here the fuel molecular mobility is indicated by the D values of the methyl and methylene peaks. Results indicate that both DMO and EG solutions have lower fuel molecular mobility than methanol. Results for the various NP-PCM also reveal reduced fuel permeability for DMO and EG compared with methanol.

Original languageEnglish
Pages (from-to)2187-2193
Number of pages7
JournalElectrochimica Acta
Volume48
Issue number14-16 SPEC.
DOIs
StatePublished - 30 Jun 2003

Keywords

  • Alternative fuels
  • Electrochemical devices
  • Fuel cells
  • Nano-porous proton conduction membranes (NP-PCM's)
  • Pulsed field-gradient NMR
  • Self-diffusion coefficient

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