(528a) Studying Stability: An Investigation of Metal to Insulator Transition Induction in Strontium Iridate Perovskites for Electrochemical Water Splitting
AIChE Annual Meeting
Wednesday, November 10, 2021 - 3:30pm to 3:45pm
To achieve this goal, we study a strontium iridate perovskite material system and employ B-site substitution (SrIrxM1-xO3) with first row transition metals (M = Zn, Ni, and Co) to tune various geometric and electronic structure properties. Each catalyst within this group of materials experiences surface rearrangement when performing OER catalysis in harsh oxidative and acidic environments, which initially improve the catalystsâ intrinsic OER activities. However, we have identified that with extensive electrochemical activity cycling this rearrangement process eventually causes a critical material instability. By using a variety of electrochemical and spectroscopic characterization techniques we have recently made the novel discovery that SrIr0.8M0.2O3 catalysts undergo a detrimental metal to insulator transition (MIT) with prolonged OER performance. Through EXAFS analysis, we provide evidence that such a transition is induced by geometric changes to the perovskite crystal structure caused by the OER. We additionally show through various B-site substitutions the rate at which a MIT is induced is effectively tuned. Lastly, we offer a fundamental understanding of the nature of MIT induction by relating total faradaic charge to number of active sites throughout a catalystâs lifetime. By uncovering this fundamental relationship, we present a novel material stability metric to assess the stability against OER-induced MIT for materials subject to the transition. As conductivity of catalysts is crucial to their electrochemical performance, it is imperative to understand the nature of the MIT to enable more informed catalyst development to ultimately improve the economics and efficiency of electrochemical water splitting for carbon-free hydrogen fuel production.