(569r) Design and Operating Principles for High-Performing Anion Exchange Membrane Water Electrolyzers

Electrolytic hydrogen will play a crucial role as a renewable energy carrier for hard-to-decarbonize sectors, particularly in heavy industry. Anion-exchange-membrane water electrolyzers (AEMWEs) have the potential to be more cost effective compared to the incumbent technology, through the use of cheaper materials compared to proton-exchange-membrane water electrolysis and higher efficiencies compared to liquid alkaline water electrolysis. However, AEMWEs are still at an early stage of development and lack established guiding design and operating principles. Herein, we study how membrane electrode assembly (MEA) component design and cell operating conditions influence the performance of AEMWEs. A custom design three-electrode MEA is used to breakdown the overpotential contributions from the anode and cathode, showing that OER still dominate kinetic losses while the cathode has more severe mass transport limitations. A significant improvement in cell performance is observed for more porous catalyst layer on the anode porous transport electrode (PTE), primarily due to a higher catalyst utilization. On the cathode, the use of a hydrophobic gas diffusion layer (GDL) improves performance at high current densities by facilitating the removal of hydrogen gas. Investigating the feed configuration with various electrolytes showed that performance was improved with a dry cathode, signifying that back diffusion of water through the membrane is sufficient to supply enough reactant. These learned principles were used to assemble a completely PGM-free AEMWE that reached 1.6 A cm^‑2 at 2 V in 1 M KOH, and exhibited stable performance in 0.1 M KOH at 1.5 A cm^‑2 for over 500 h.