Nonhumidified Intermediate Temperature Fuel Cells Using Protic Ionic Liquids
Top Cited Papers
- 28 June 2010
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 132 (28), 9764-9773
- https://doi.org/10.1021/ja102367x
Abstract
In this paper, the characterization of a protic ionic liquid, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), as a proton conductor for a fuel cell and the fabrication of a membrane-type fuel cell system using [dema][TfO] under nonhumidified conditions at intermediate temperatures are described in detail. In terms of physicochemical and electrochemical properties, [dema][TfO] exhibits high activity for fuel cell electrode reactions (i.e., the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR)) at a Pt electrode, and the open circuit voltage (OCV) of a liquid fuel cell is 1.03 V at 150 degrees C, as has reported in ref 27. However, diethylmethylammonium bis(trifluoromethane sulfonyl)amide ([dema][NTf(2)]) has relatively low HOR and ORR activity, and thus, the OCV is ca. 0.7 V, although [dema][NTf(2)] and [dema][TfO] have an identical cation ([dema]) and similar thermal and bulk-transport properties. Proton conduction occurs mainly via the vehicle mechanism in [dema][TfO] and the proton transference number (t(+)) is 0.5-0.6. This relatively low t(+) appears to be more disadvantageous for a proton conductor than for other electrolytes such as hydrated sulfonated polymer electrolyte membranes (t(+) = 1.0). However, fast proton-exchange reactions occur between ammonium cations and amines in a model compound. This indicates that the proton-exchange mechanism contributes to the fuel cell system under operation, where deprotonated amines are continuously generated by the cathodic reaction, and that polarization of the cell is avoided. Six-membered sulfonated polyimides in the diethylmethylammonium form exhibit excellent compatibility with [dema][TfO]. The composite membranes can be obtained up to a [dema][TfO] content of 80 wt % and exhibit good thermal stability, high ionic conductivity, and mechanical strength and gas permeation comparable to those of hydrated Nafion. H(2)/O(2) fuel cells prepared using the composite membranes can successfully operate at temperatures from 30 to 140 degrees C under nonhumidified conditions, and a current density of 250 mA cm(-2) is achieved at 120 degrees C. The protic ionic liquid and its composite membrane are a possible candidate for an electrolyte of a H(2)/O(2) fuel cell that operates under nonhumidified conditions.Keywords
This publication has 68 references indexed in Scilit:
- High temperature PEM fuel cellsJournal of Power Sources, 2006
- Alternative Polymer Systems for Proton Exchange Membranes (PEMs)Chemical Reviews, 2004
- Transport in proton conductors for fuel-cell applications: Simulations, elementary reactions, and phenomenologyChemical Reviews, 2004
- Approaches and Recent Development of Polymer Electrolyte Membranes for Fuel Cells Operating above 100 °CChemistry of Materials, 2003
- Preparation and characterization of matrix retaining electrolyte for a phosphoric acid fuel cell by non-volatile solvent, NMPJournal of Power Sources, 2003
- Effect of silicon carbide particle size in the electrolyte matrix on the performance of a phosphoric acid fuel cellJournal of Power Sources, 2002
- Approaches and technical challenges to high temperature operation of proton exchange membrane fuel cellsJournal of Power Sources, 2001
- Preparation and characterization of matrices for phosphoric acid fuel cellsJournal of Applied Electrochemistry, 1997
- Acid‐Doped Polybenzimidazoles: A New Polymer ElectrolyteJournal of the Electrochemical Society, 1995
- Heat-treated polyacrylonitrile-based catalysts for oxygen electroreductionJournal of Applied Electrochemistry, 1989