# Use of Poly(styrene-co-acrylic Acid) in a Composite Ion-Solvating Membrane for Water Electrolysis

## TL;DR

A new composite membrane made with poly(styrene-co-acrylic acid) improves water electrolysis performance and durability.

## Contribution

A novel composite ion-solvating membrane with high ion exchange capacity and mechanical strength is developed for alkaline water electrolysis.

## Key findings

- The membrane achieved a through-plane conductivity of 24 mS cm–1 at 70 °C with 4 M KOH.
- The membrane showed a cell voltage of 1.89 V at 1 A cm–2 current density in an electrolyzer.
- No degradation was observed after 720 hours of aging and 150 hours of electrolysis testing.

## Abstract

Ion-solvating membranes
(ISMs) have recently emerged as a promising
class of materials for alkaline water electrolysis. Their non microporous
polymer architecture and the absence of alkaline labile functional
groups pave the way for a new generation of hybrid electrolyzers that
combine the key features and advantages of conventional alkaline water
electrolyzers (AWE) with those of proton exchange membrane water electrolyzers
(PEMWE). Herein, a styrene-acrylic acid copolymer was synthesized
and deposited onto a commercial microporous polypropylene support,
yielding a composite ISM that couples an ion exchange capacity (IEC)
of 2.72 mmol g–1 with good mechanical properties
(tensile strength of 65 MPa). The electrochemical performance of the
membranes was evaluated by through-plane conductivity measurements
(24 mS cm–1, with KOH 4 M at 70 °C) and operation
in an electrolyzer cell (reaching a cell voltage of 1.89 V at a current
density of 1 A cm–2, with KOH 4 M at 70 °C).
Polymer stability was assessed by monitoring structural changes via 1H NMR spectroscopy after an aging treatment in KOH 4 M at
70 °C for 720 h. Additionally, long-term electrolysis was investigated
through a discontinuous cell test over 150 h. No detectable signs
of degradation were observed in either test.