Composite anion exchange membranes based on polysulfone and silica nanoscale ionic materials for water electrolyzers

Anion exchange membrane water electrolysis (AEMWE) offers the ambition of combining the advantages of alkaline electrolysers, i.e. the use of cheap and plentiful catalytic materials, with those of proton exchange membrane electrolysis of water, i.e. 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. Here, we introduce an innovative nanocomposite AEM based on trimethylammonium functionalized silica nanoscale ionic materials (NIM-N) incorporated in quaternized polysulfone (qPSU). The presence of NIM-N in the hydrophilic clusters of qPSU produces a remarkable enhancement in the dimensional and thermo-mechanical stability of the composite AEM. Furthermore, Nuclear Magnetic Resonance (NMR) and Electrochemical Impedance Spectroscopy (EIS) investigations highlighted that the nanoparticles are directly involved in the transport process of hydroxide ions. This enabled qPSU/NIM-N composite membrane to achieve impressive anionic conductivity values, e.g. about 110 mS cm at 80 °C and 95% relative humidity (RH). The AEMWE single cell, equipped with this membrane, operated properly both with 1 or 0.5 M KOH solution, displaying a current density larger than 3.5 A cm at 2.2 V and 80 °C.