Development of crosslinked SEBS-based anion exchange membranes for water electrolysis: Investigation of the crosslinker effect

• Published in: International journal of hydrogen energy 2023-07, Vol.48 (63), p.24180-24195
• Main Authors: Lee, Junghwa, Min, Kyungwhan, Jeon, Soomin, Park, Sanggil, Kim, Hyungjun, Kim, Tae-Hyun
• Format: Article
• Language: English
• Subjects: Anion exchange membranes; Crosslinker effect; Hydrogen bonding; Poly(styrene-b-(ethylene-co-butylene)-b-styrene); Water electrolysis
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.03.143

SEBS (styrene-b-(ethylene-co-butylene)-b-styrene)) is a non-aryl-ether-type tri-block copolymer widely used as an anion exchange membrane (AEM) material due to its excellent alkaline stability and phase separation properties. However, low tensile strength due to the aliphatic chains and the poor physical properties of the SEBS-based membranes limit their practical application for AEM water electrolysis (AEMWE) or AEM fuel cell (AEMFC). In this study, three types of crosslinked AEMs were prepared using bromohexyl pentafluorobenzyl SEBS as a polymer backbone, and three different crosslinkers, dimethyl amine (DMA), tetramethyl diaminohexane (TMHA), and tris(dimethyl aminomethyl) phenol (TDMAP). Once introduced, these crosslinking agents were converted into the corresponding conducting head groups. The thermal, chemical, physical, and electrical properties of the obtained crosslinked membranes were then investigated for use in AEMWE. In particular, the TDMAP-50x-SEBS membrane with 50% degree of crosslinking experienced hydrogen bonding with water and OH− due to the presence of OH groups in the structure of the crosslinking agent (TDMAP). Because of this, the membrane showed an improved morphology and high conductivity (20 °C: 31.8 mS cm−1, 80 °C: 109.9 mS cm−1). In addition, TDMAP induced physical crosslinking by hydrogen bonding between molecules so that the corresponding membrane (TDMAP-50x-SEBS) exhibited high alkaline and oxidative stability and good mechanical properties. This SEBS-based membrane has a tensile strength of 18.0 MPa and Young's modulus of 165.14 MPa. The WE single-cell test (1 M KOH solution at 70 °C) using TDMAP-50x-SEBS also showed a cell performance of 1190 mA cm−2 at 2.0 V. This is 126% higher than the cell performance measured for FAA-3-50, a commercialized AEM material, under the same conditions. [Display omitted] •Crosslinked AEMs were prepared using three different crosslinkers.•Tris (dimethyl aminomethyl) phenol (TDMAP) were used as a new conducting head group.•OH groups on the TDMAP enhanced the conductivity, stability and cell performance of AEM.