Porous organic polymers as ionomers for high-performance alkaline membrane water electrolysis

Abstract

The pressing nature of the climate emergency, coupled with the depletion of fossil fuel reserves, underscores the critical need for renewable energy alternatives, in which green hydrogen is recognized as a viable, environmentally sustainable energy option that has gained substantial interest in recent years.Unlike methods dependent on petroleum processing, green hydrogen production revolves around water splitting through electrolysis, powered by electricity generated from solar power or other renewable sources, and it has been suggested as a pathway to achieve carbon neutrality within the coming decades. Traditional alkaline water electrolyzers typically employ highly concentrated alkaline solutions, presenting drawbacks such as accelerated corrosion, and vulnerability to ambient CO2, leading to electrode blockages and reduced conductivity. In response to these challenges, polymer electrolyte water electrolysis systems like proton exchange membrane water electrolyzers and AEMWEs have emerged as prominent solutions. The main component of the AEMWE system is the membrane electrode assembly (MEA), consisting of an AEM, ionomers, and catalysts. The AEM acts as a barrier, separating the anode and cathode electrodes to prevent gas crossover, whereas the ionomers act as binders, linking or stabilizing catalyst particles while facilitating ion transport. Over the past decades, significant advancements have been achieved in highperformance AEM development. However, the significance of ionomer design often goes unnoticed. Typically, ionomers are chosen with identical or similar structures as AEMs, yet the different working conditions of AEMs and ionomers require different properties. Ionomers must possess high water and gas permeability, electrochemical stability, and low catalyst adsorption ability.