High-performance anion exchange membrane water electrolysis by polysulfone grafted with tetramethyl ammonium functionalities

'Green' hydrogen production using anion exchange membrane (AEM) water electrolysis is one of the most promising approaches to address the severe energy crisis facing human society. However, to enable commercially viable hydrogen generation, huge improvement in the AEM technology is imperative, including membrane stability, higher operating temperature, ion conductivity, power performance, and cost reduction. Herein, a novel anion conductive membrane for water electrolysis is synthesized using low-cost and eco-friendly polysulfone as the base polymer, while chemical grafting of quaternary ammonium functionalities has been exploited to confer anion conductive properties. The physicochemical features, the mechanical properties, and the electrochemical performance were widely investigated by a combination of various techniques including DMA, pulsed field gradient nuclear magnetic resonance spectroscopy, electrochemical impedance spectroscopy, and linear sweep voltammetry in an electrolysis cell. The quaternary-ammonium-modified polysulfone (qPSU) membrane exhibited impressive hydrolytic and mechanical stabilities as a result of a nanophase segregation between hydrophilic/hydrophobic domains in such electrolytes. The latter feature enables the formation of wide percolating ion clusters in the qPSU AEM, which form a highly interconnected pathway for efficient hydroxide conduction. Water electrolysis single cells equipped with this membrane reached the remarkable current density of 4.2 A/cm at 2.2 V and 90 °C.