Multication Side Chain Anion Exchange Membranes

Abstract

Anion exchange membrane fuel cells (AEMFCs) have been developed as promising energy conversion devices for stationary and mobile applications due to their potentially low cost. To realize high-performance AEMFCs, new polymeric membranes are needed that are highly conductive and chemically stable. Here we report a systematic study of anion exchange membranes (AEMs) with multiple cations per side chain site to demonstrate how this motif can boost both the conductivity and stability of poly­(2,6-dimethyl-1,4-phenylene oxide)-based AEMs. The highest conductivity, up to 99 mS/cm at room temperature, was observed for a triple-cation side chain AEM with 5 or 6 methylene groups between cations. This conductivity was considerably higher than AEM samples based on benzyl­trimethyl­ammonium or benzyl­dimethylhexyl­ammonium groups with only one cation per side chain site. In addition to high conductivity, the multication side chain AEMs showed good alkaline and dimensional stabilities. High retention of ion exchange capacity (IEC) (93% retention) and ionic conductivity (90% retention) were observed for the triple-cation side chain AEMs in degradation testing under 1 M NaOH at 80 °C for 500 h. Based on the high-performance triple-cation side chain AEM, a Pt-catalyzed fuel cell with a peak power density of 364 mW/cm2 was achieved at 60 °C under 100% related humidity.

Main‐chain poly(1,2,3‐triazolium hydroxide)s obtained through AA+BB click polyaddition as anion exchange membranes

“…However, it is difficult to establish a clear relationship between σ and IEC as for both counter‐ions a plateau value seems to be reached above ca IEC NMR‐OH = 1.5 meq g −1 independently of the chemical nature of the diazide monomer while the corresponding WU values range from 27% to 144%, suggesting that the increase of ionic content onto the polymer chain is counterbalanced by its dilution into the hydrated membrane. Comparable evolutions in this range of IEC values were previously observed for quaternary ammonium hydroxide based AEMs . Yet, the 10‐fold increase in σ for hydroxide anions compared to iodide anions is in good agreement with the literature and confirms the larger mobility of the hydroxide anions .…”

“…Besides, while most AEMs are based on polymer electrolytes having side‐chain cationic moieties, the materials studied herein contain main‐chain 1,2,3‐triazolium groups. As highlighted earlier, the location and the presence of a spacer between the polymer backbone and the ion pairs significantly impact the microstructure and ionic conductivity of AEMs. Optimizing the macromolecular architecture of PTIL hydroxides would thus certainly allow membrane properties to be improved.…”

Octa‐imidazolium POSS/quaternized polysulfone composite anion exchange membrane for alkaline fuel cell

“…Among the various renewable technologies, high efficiency with less or zero emissions created a remarkable research interest in fuel cells across the world . In recent times, alkaline fuel cell utilizing anion exchange membrane (AEM) has gained increasing attention over the acidic fuel cell functioning with proton exchange membrane (PEM) . AEMs, also referred as solid anion‐conducting polymer electrolytes, are composed of positively charged groups grafted on high engineering polymers .…”

Dual-cation comb-shaped anion exchange membranes: Structure, morphology and properties

“…Changing trend of the conductivity with the side chain functionalization degree was investigated [25]. Hickner's research group evaluated the properties of a series of AEMs with the multi-cation functionalized side chain, excellent fuel cell performance was observed for the tri-cation based AEM [26].…”