Covalent catalyst immobilization in cross-linked ionomers for durable pure water anion exchange membrane electrolysis

Anion exchange membrane water electrolysis technology, which employs alkaline electrolytes, has emerged as a highly promising alternative to the acidic counterparts. However, the development of pure water-fed anion exchange membrane water electrolysis remains in its nascent stage, hindered by suboptimal ionomer performance, along with an unstable catalyst-ionomer interface induced by the Marangoni effect during the fabrication of catalyst layers. In this study, we introduce a strategy to overcome these challenges by employing in-situ covalent anchoring of the catalyst within cross-linked ionomer networks. Through synchrotron X-ray three-dimensional computed tomography characterization, complemented by extensive electrochemical analysis and multiphysics simulations, we demonstrate that the interconnected ionomer network substantially improves mass transport properties. Additionally, the covalently locked interfacial bonding effectively addresses delamination issues. Under rigorous pure water-fed conditions, our crosslink-immobilized catalyst layer demonstrates competitive durability (>1800 hours with a decay rate of 0.03 mV h^-1) and performance (2.55 A cm^-2 at 1.9 V). This approach presents an alternative paradigm for fabricating mechanically robust catalyst layers with enhanced durability and performance.