Enabling Improved Durability Ruthenium Oxide Acidic Oxygen Evolution Electrocatalysts

Acidic oxygen evolution reaction (OER) electrocatalysts with high activity, extended durability, and lower costs are needed to expand the utilization of proton-exchange membrane (PEM) water electrolyzers that generate hydrogen from water and electricity. Although iridium-based catalysts are currently the primary OER catalysts used within PEM electrolyzers, ruthenium has a higher activity, lower cost, and higher global supply compared to iridium. However, ruthenium-based OER catalysts generally have lower stability compared to iridium-based catalysts. We are investigating how crystal structure, substituents, and surface reconstruction affect the activity and stability of acidic ruthenium oxide OER catalysts. Our work has explored the effects of titanium substitution into rutile RuO 2 on OER activity and metal dissolution using accelerated durability tests. 1,2 Exposure to highly oxidative potentials, where oxygen evolution and metal dissolution occur, results in surface reconstruction and changes to the active catalytic sites and OER activity. The OER-specific activity evolves with cycling, with significant differences observed between RuO 2 and Ru 0.8 Ti 0.2 O 2 . While the OER-specific activity of RuO 2 initially increases and then decreases, the OER-specific activity of Ru 0.8 Ti 0.2 O 2 increases and then remains stable with further cycling. Ru 0.8 Ti 0.2 O 2 showed a 19 times lower Ru dissolution rate than RuO 2 . Scanning transmission electron microscopy analysis supports that repeated cycling under OER conditions results in surface reconstruction for RuO 2 and Ru 0.8 Ti 0.2 O 2 . RuO 2 particles form a disordered surface (~1-2 nm thick) after cycling. Electron energy loss spectroscopy analysis indicates that after cycling, Ru-O bonding within the surface is altered compared to the pristine material. Our recent work is exploring ruthenium-based pyrochlores (M 2 Ru 2 O 7 ), based on their high tolerance for lattice distortion and potential for improved electrochemical stability. Our work furthers understanding of how crystal structure, substituents, and surface reconstruction affect OER catalytic activity and degradation, which can lead to the development of improved OER electrocatalysts. References Ospina-Acevedo, F.; Godínez-Salomón, J.F.; Naymik, Z.G.; Matthews, K.C.; Warner, J.H.; Rhodes, C.P.; Balbuena, P.B. Impacts of Surface Reconstruction and Metal Dissolution on Ru 1-x Ti x O 2 Acidic Oxygen Evolution Electrocatalysts, Journal of Physical Chemistry C 2025 , 129, 3595–3613 . DOI: 10.1021/acs.jpcc.4c08119. Godinez-Salomon, J. F.; Ospina-Acevedo, F.; Albiter, L. A.; Bailey, K. O.; Naymik, Z. G.; Mendoza-Cruz, R.; Balbuena, P. B.; Rhodes, C. P. Titanium Substitution Effects on the Structure, Activity, and Stability of Nanoscale Ruthenium Oxide Oxygen Evolution Electrocatalysts: Experimental and Computational Study. ACS Appl. Nano Mater. 2022 , 5 (8), 11752–11775. DOI: 10.1021/acsanm.2c02760. Godínez-Salomón, F.; Albiter, L.; Alia, S.; Pivovar, B.; Forero, L. C.; Balbuena, P.; Mendoza-Cruz, R.; Arellano-Jimenez, M. J.; Rhodes, C. P. Self-Supported Hydrous Iridium-Nickel Oxide Two-dimensional Nanoframes for High Activity Oxygen Evolution Electrocatalysts. ACS Catal. 2018 , 8 , 10498-10520. DOI: 10.1021/acscatal.8b02171