(308c) Insights into the Factors That Govern the Stability of Ru-Based Nonstoichiometric Mixed Metal Oxides during Acidic Oxygen Evolution Reaction.

Oxygen evolution reaction (OER) has attracted significant interest in recent years due to its crucial role in sustainable electrochemical energy conversion and storage devices for renewable energy applications¹. Precious metal-based oxide (e.g., RuO₂)² currently serves as a benchmark OER catalyst due to its high activity in acidic media, however, its instability, scarcity and high cost impedes commercial use³. Implementation of mixed metal oxides with varying crystal structures shows promise due to their low precious metal content and high activity and stability for acid OER³ however precise origins of these characteristics are still elusive. Though progress has been made in terms of rationalizing activity trends using bulk oxide properties such as the Ru 4d – O 2p overlap⁴, the key descriptors that dictate stability are still unknown⁵. Herein, variations of the A-site of the Ru based mixed metal oxides (ABO₃ or A₂B₂O₇; A = alkaline earth metal and/or lanthanide cation; B = Ru) are probed to correlate changes in their oxide reducibility with the activity and stability for acidic OER. Using a combination of electrochemical measurements, mass spectrometry, and X-ray based spectroscopic techniques, we provide an understanding of the structural evolution of these oxide surfaces in relation to their surface properties. These findings are critical toward developing the necessary understanding needed to design robust, new generation of OER electrocatalysts.

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(5) Gu, X.-K., et.al., Chem. Mater, 2018, 30 (9), 2860–2872.