Design and operating principles for high-performing anion exchange membrane water electrolyzers

Anion-exchange-membrane water electrolyzers (AEMWEs) provide a promising pathway to utilize low-carbon renewable electricity to produce clean hydrogen at high efficiency and purity, while maintaining low system costs compared to incumbent technologies. Though significant progress has been made in developing membranes and catalysts, AEMWEs still require better performance and durability to realize widespread deployment. Here, we overcome these challenges by decoupling anode and cathode polarization behavior via integration of a reference electrode in the membrane-electrode assembly. This measurement identified that the mass-transport losses dominate the cathode overpotential if feeding with electrolytes, while kinetic losses dominate the anode overpotential. These losses are mitigated by varying electrode properties and operating strategies, where a more hydrophobic, optimal loaded cathode, a high porosity anode, and operating with the cathode dry exhibited the best performance. These findings eventually enabled achieving a high-performing and durable complete PGM-free AEMWE operating at 1.5 A cm−2 for over 500 h with negligible degradation, demonstrating significant progress for AEMWEs. [Display omitted] •Analyze the sources of overpotential for AEMWEs.•Provide electrode design strategies for high-performing AEMWEs.•Highlight importance of water back-diffusion from anode to cathode for AEMWEs.•Investigate the impact of feeding configurations on AEMWE performance.•Achieve AEMWEs of 4 A/cm2