Novel proton-exchange membrane based on single-step preparation of functionalized ceramic powder containing surface-anchored sulfonic acid

S. Reichman, L. Burstein, E. Peled*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A novel approach to the synthesis of a low-cost proton-exchange membrane (PEM) based on the single-step preparation of a functionalized ceramic powder containing surface-anchored sulfonic acid (SASA) and a polymer binder, is presented for the first time. The added value of this technique, compared with earlier work published by our group, is the adoption of a direct, single-step synthesis, as opposed to a multiple-step synthesis. The latter requires an oxidation step, in order to convert the thiol group into a sulfonic group. SASA powders of different compositions have been prepared and characterized by means of Brunaur-Emmet-Teller (BET), thermogravimetric analysis-differential thermal analysis (TGA-DTG), differential scanning calorimeter (DSC), Fourier transformation infrared (FT-IR), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and electrochemical techniques. The lowest equivalent weight measured for SASA powders is 1281 g equiv.-1. The ionic conductivity of a 100-μm-thick membrane is measured ex situ at room temperature (25 ± 3 °C) and the highest proton conductivity is 48 mS cm-1. The typical pore size, for the SASA powders is less than 10 nm and ranges from 2 to 50 nm for the SASA-based membranes. The membranes are thermally stable up to 250 °C. Direct methanol fuel cells (DMFCs) are assembled with some of the membranes. Preliminary tests showed that the cell resistance for a ∼100-μm-thick membrane ranges between 0.29 and 0.19 Ω cm2 from 80 to 130 °C, respectively, and that the maximum cell power density with a 1 M methanol solution is 127, 208 and 290 mW cm-2 at 80, 110 and 130 °C, respectively, while the corresponding methanol crossover current density is 0.093, 0.238 and 0.281 A cm-2.

Original languageEnglish
Pages (from-to)520-531
Number of pages12
JournalJournal of Power Sources
Volume179
Issue number2
DOIs
StatePublished - 1 May 2008

Keywords

  • Composite proton-exchange membrane
  • Direct methanol fuel cell
  • Functionalized ceramic powder
  • Membrane electrode assembly
  • Power density
  • Surface-anchored sulfonic acid

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