Imidazolium Cations with Exceptional Alkaline Stability: A Systematic Study of Structure-Stability Relationships.

Highly base-stable cationic moieties are a critical component of anion exchange membranes (AEMs) in alkaline fuel cells (AFCs); however, the commonly employed organic cations have limited alkaline stability. To address this problem, we synthesized and characterized the stability of a series of imidazolium cations in 1, 2, or 5 M KOH/CD3OH at 80 °C, systematically evaluating the impact of substitution on chemical stability. The substituent identity at each position of the imidazolium ring has a dramatic effect on the overall cation stability.

An electrochemical quartz crystal microbalance study of a prospective alkaline anion exchange membrane material for fuel cells: anion exchange dynamics and membrane swelling.

A strategy has been devised to study the incorporation and exchange of anions in a candidate alkaline anion exchange membrane (AAEM) material for alkaline fuel cells using the electrochemical quartz crystal microbalance (EQCM) technique. It involves the electro-oxidation of methanol (CH3OH) under alkaline conditions to generate carbonate (CO3(2-)) and formate (HCOO(-)) ions at the electrode of a quartz crystal resonator coated with an AAEM film, while simultaneously monitoring changes in the frequency (Δf) and the motional resistance (ΔR(m)) of the resonator. A decrease in Δf, indicating an apparent mass increase in the film, and a decrease in ΔR(m), signifying a deswelling of the film, were observed during methanol oxidation.

Phosphonium-functionalized polyethylene: a new class of base-stable alkaline anion exchange membranes.

A tetrakis(dialkylamino)phosphonium cation was evaluated as a functional group for alkaline anion exchange membranes (AAEMs). The base stability of [P(N(Me)Cy)(4)](+) was directly compared to that of [BnNMe(3)](+) in 1 M NaOD/CD(3)OD. The high base stability of [P(N(Me)Cy)(4)](+) relative to [BnNMe(3)](+) inspired the preparation of AAEM materials composed of phosphonium units attached to polyethylene.

Tunable high performance cross-linked alkaline anion exchange membranes for fuel cell applications.

Fuel cells are energy conversion devices that show great potential in numerous applications ranging from automobiles to portable electronics. However, further development of fuel cell components is necessary for them to become commercially viable. One component critical to their performance is the polymer electrolyte membrane, which is an ion conductive medium separating the two electrodes.

A ring-opening metathesis polymerization route to alkaline anion exchange membranes: development of hydroxide-conducting thin films from an ammonium-functionalized monomer.

We report the development of a facile ring-opening olefin metathesis route to alkaline anion exchange membranes via the copolymerization of a tetraalkylammonium-functionalized norbornene with dicyclopentadiene. The thin films generated are mechanically strong and exhibit high hydroxide conductivities and exceptional methanol tolerance.