Novel Pyrrolidinium-Functionalized Styrene-b-ethylene-b-butylene-b-styrene Copolymer Based Anion Exchange Membrane with Flexible Spacers for Water Electrolysis

Abstract

Anion exchange membranes (AEM) are core components for alkaline electrochemical energy technologies, such as water electrolysis and fuel cells. They are regarded as promising alternatives for proton exchange membranes (PEM) due to the possibility of using platinum group metal (PGM)-free electrocatalysts. However, their chemical stability and conductivity are still of great concern, which is appearing to be a major challenge for developing AEM-based energy systems. Herein, we highlight an AEM with styrene-b-ethylene-b-butylene-b-styrene copolymer (SEBS) as a backbone and pyrrolidinium or piperidinium functional groups tethered on flexible ethylene oxide spacer side-chains (SEBS-Py2O6). This membrane reached 27.8 mS cm−1 hydroxide ion conductivity at room temperature, which is higher compared to previously obtained piperidinium-functionalized SEBS reaching up to 10.09 mS cm−1. The SEBS-Py206 combined with PGM-free electrodes in an AWE water electrolysis (AEMWE) cell achieves 520 mA cm−2 at 2 V in 0.1 M KOH and 171 mA cm−2 in ultra-pure water (UPW). This high performance indicates that SEBS-Py2O6 membranes are suitable for application in water electrolysis.

Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance

“…In addition, both area swelling (28%) and thickness swelling values (29%) for P(OB73pip-TFAP) are higher than those of P(OB70pyr-TFAP) at 80 °C (11% and 14%, respectively), probably owing to the larger piperidine moiety facilitating the formation of bigger ionic clusters [ 43 ] and its slightly higher IEC. These results are in accordance with those reported in the literature [ 27 , 43 , 44 , 45 ]. Both membranes exhibit low swelling values attributed to the presence of flexible hydrophobic alkyl chains, which increase the volume fraction of hydrophobic domains, thereby restricting swelling and thus ensuring the good mechanical properties for application in alkaline water electrolyzers.…”

Porous PTFE supported bis(siloxane imidazole) functionalized Norbornyl copolymer composite anion exchange membrane for alkaline fuel cells

“…Alkaline stability is another pivotal parameter besides hydroxide conductivity in practical applications for AEMs 57 . The alkaline stability of the PTFE/CLm‐aP(NB‐MGE‐ b ‐NB‐MHE) membranes was evaluated by soaking the AEMs in a 1 M NaOH solution at 60°C.…”

“…Alkaline stability is another pivotal parameter besides hydroxide conductivity in practical applications for AEMs. 57…”

Recent progress in anion exchange membranes (AEMs) in water electrolysis: synthesis, physio-chemical analysis, properties, and applications

“…345 Thus, the KOH solution that uses the AEMWE system can potentially attain higher results. Similarly, longer side chain-crosslinked pyrrolidinium-functionalized membranes, such as SEBS-Py206, demonstrate greater current densities (0.5 A cm −2 ), which were achieved in the presence of 0.1 M KOH, compared to lower current densities (0.17 A cm −2 ) when using pure water and a cell voltage of 2 V. 346 Nevertheless, the current density of the SEBS-Py206 was lower than SEBS-P206 AEMs in this study's testing of water electrolysis using a PGM-free catalyst or conductivity issues. Triazole may be utilized to crosslink the two polymers to enhance the AEMWE performances and mechanical qualities.…”