Porous Organic Polymers as Ionomers for High‐Performance Alkaline Membrane Water Electrolysis

Sustainable hydrogen production is focused on anion exchange membrane (AEM) water electrolyzers (AEMWEs), which still require more development to achieve high performance and durability. Here, we propose a novel class of porous organic polymers (POPs) as durable solid-ionomers for AEMWEs, which was prepared by reacting the 4-methylpiperidone with trifunctional or a mixture of trifunctional:difunctional aromatic monomers (in a 2 : 3 mol ratio). The resulting POP ionomers exhibited exceptional electrochemical properties and remarkable alkaline stability. Particularly noteworthy are the corresponding AEMWEs, which showed an outstanding current density of 13.4 A cm^-2 at 2.0 V under 80 °C in 1 M KOH solution, which is the highest performance reported in the particulate-ionomers AEMWE state of the art. Moreover, they demonstrated durability at a current density of 0.5 A cm^-2 for over 500 h with a voltage decay rate of 120 μV h^-1. This work offers valuable perspectives on the designing of robust and high-performance solid-state ionomers through low-cost electrophilic aromatic substitution reactions for high-performance energy conversion devices.