Investigating Yttrium Ruthenate Pyrochlore as an Anodic Electrocatalyst in Proton Exchange Membrane Water Electrolysis

Abstract: As the energy transition progresses, the demand for green storage solutions is ever-increasing. Hydrogen storage is receiving increased interest and support due to its promising sustainability and flexibility. Proton-exchange, or polymer electrolyte, membrane (PEM) electrolyzers are a key technology supporting hydrogen storage systems. Reducing anodic catalysts costs by proposing alternatives to the standard and expensive rare-earth metal oxide catalysts are key to accelerating commercialization of PEM water electrolyzers. Yttrium ruthenate pyrochlore Y2Ru2O7 (YRO) has stood out as promising alternative due to enhanced oxygen evolution reaction (OER) activity, high stability, and low onset overpotential in acidic PEM conditions. Obstacles remain, including low electrical conductivity. This work investigates YRO as a suitable OER catalyst for PEM water electrolysis. In assessing the catalyst suitability, the impacts of pre-calcination in sol-gel synthesis of YRO, mechanical post-processing of powders, and ink preparation on result quality and catalyst performance are unveiled via rotating disc electrode (RDE) characterization. Pre-calcination, grinding and milling, and lengthy and cooled sonication of inks contribute to improved results quality. A half-cell apparatus is developed and verified as a proof of concept for increased electrochemical characterization flexibility and improved representation of electrolyzer operational conditions. Test station membrane electrode assembly (MEA) characterization reveals undoped YRO undergoes severe and irreversible degradation as a single component catalyst in PEM electrolysis. Hydrogen crossover and low electrical conductivity are chief drivers for the high losses and degrading performance.