2024 AIChE Annual Meeting
Renewable Hydrogen Production: In-Plane Electrical Conductivity of Polymer Electrolyte Membrane Water Electrolysis (PEMWE) Catalyst Layers for Performance Study
Rising carbon dioxide emissions due to fossil fuels raise the importance of developing renewable energy alternatives for energy conversion and storage. Proton exchange membrane water electrolysis (PEMWE) has been proposed as a promising energy-dense method for green hydrogen production. However, PEMWE is associated with high costs, prominently due to the iridium anode catalyst. Ultra-low iridium loading (~.1 mg/cm2) with added supports can reduce electrolyzer costs and optimize performance. However, ultra-low-loading catalyst layers may display less uniformity and lower in-plane conductivity. This research aims to understand and correlate the relationship between in-plane electrical conductivity, anode iridium catalyst loading, adding iridium supports, catalyst uniformity, and cell performance. Methods were first developed for in-plane electrical conductivity measurements of anode catalyst layers using a four-point probe. Experimentally, catalyst-coated membrane (CCM) and decal in-plane conductivity were measured and compared for TiOₓ-supported IrO₂ (IrO₂/TiOₓ), NbOₓ-supported IrO₂ (IrO₂/NbOₓ), mixed TiOₓ-NbOₓ-supported IrO₂ and Tanaka 110 (TKK110, pure iridium). Results confirmed an inverse relationship between iridium catalyst loading and sheet resistance as predicted, with higher sheet resistance at ultra-low loading that may be attributed to catalyst non-uniformity. IrO₂/TiOₓ featured greater conductivity than IrO₂/NbOₓ and much higher conductivity than TKK110. Ultra-low loading IrO₂/TiOₓ and IrO₂/NbOₓ samples displayed durability and minimal degradation under Accelerated Stress Test (AST) protocol compared to TKK110, correlating increased in-plane conductivity with strong cell performance. This research on in-plane electrical conductivity with supported ultra-low loading anode catalysts progresses PEMWE performance characterization for future large-scale implementation of PEMWE and lower-cost renewable energy.