(Invited) Development of Cost-Effective Anion Exchange Membranes for Water Electrolyzers

Abstract

Anion exchange membrane water electrolysis (AEMWE) offers the possibility of combining the advantages of alkaline electrolyzers, which allows the use of cheap and plentiful catalytic materials, with those of proton exchange membrane electrolysis, such as high performance and fast response to changing operating conditions. However, the development of performing and durable anion exchange membranes is still the major challenge for the ultimate industrial adoption of AEMWE [1]. The anion-exchange membrane (AEM) is a crucial component that should allow good charge and water transport, i.e. high ionic conductivity, but should also guarantee good chemical, thermal, and mechanical stability.In this paper, commercial and innovative membranes, also based on a nanocomposite approach, are investigated in AEMWE in terms of performance and stability. Fumasep® FAA3-50 (FumaTech) and PiperIon® (Versogen) membranes were used as benchmark materials to compare the results obtained with the novel materials developed among the partners of an Italian project called AMPERE (FISR2019 call). An anion exchange membrane was synthesized from polysulphone (PSU), which was properly functionalized through the introduction of quaternary ammonium functionalities on the polymeric backbone (qPSU) by using an optimized synthetic procedure, to achieve adequate hydrophilicity features, while preserving its mechanical properties [2]. Furthermore, an innovative nanocomposite AEM based on trimethylammonium functionalized silica nanoscale ionic materials (NIM-N+) incorporated in quaternized polysulfone (qPSU) was developed and investigated [3].Other composite membranes including graphene oxide (GO) as the filler were analyzed to increase the ion conductivity and the stability of the membrane based on commercial Fumion® ionomer.Finally, the investigation comprised the very promising class of AEMs based on poly(aryl piperidiniums)s (PAPs), which combine a heteroatom-free backbone with the stable piperidinium cationic group. The simplest and less-expensive chemistry in this family is poly(biphenyl piperidinium), which was synthesized with suitable mechanical properties for use in water electrolyzers [4].An overview of the electrochemical results obtained with the above-mentioned AEMs in single-cell electrolyzers is presented and discussed.