Bimetallic Oxygen Evolution Electrocatalysts: Relationships of Structure, Activity and Stability

Abstract

Acidic oxygen evolution reaction (OER) electrocatalysts that have high activity, extended durability, and lower costs are needed to further the development of proton-exchange membrane (PEM) electrolyzers. Within acidic OER catalysts, stability remains a critically important but significantly less studied factor relative to activity. Our work involves investigating relationships between structure, activity, and stability within bimetallic acidic OER electrocatalysts. Bimetallic catalysts that interact iridium or ruthenium with non-noble metals provide an approach to lower the amount of noble metal and increase the OER activity and stability. Non-noble metals have different electronegativities and atomic radii compared to iridium and ruthenium which alters the surface atomic and electronic structure and influences both OER activity and metal dissolution. Our prior work showed that the inclusion of nickel or cobalt within iridium-metal two-dimensional nanoframes resulted in differences in the surface structure that significantly changed the OER activity and electrochemical degradation.1,2 Bimetallic structures can undergo very different degradation processes compared to monometallic structures, as shown by our prior study.1 Our recent work has explored the effects of interacting non-noble metals within ruthenium oxide on the structure, OER activity and stability. Nanostructured bimetallic oxides were synthesized using solution-phase chemistry and through utilizing various temperature/atmosphere treatments. The synthesis and processing conditions significantly affected the resulting material’s structure and properties. The materials’ composition, morphology and structure are probed using energy dispersive X-ray spectroscopy, scanning electron microscopy, nitrogen physisorption, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Rotating disk electrode measurements are used to evaluate the electrochemical oxygen evolution activity and stability of the bimetallic oxides which were compared to baseline OER catalysts. Metal dissolution that occurs during accelerated durability testing is evaluated using inductively coupled mass spectroscopy measurements. Our recent efforts towards understanding the relationships between structure, activity, and stability within nanostructured bimetallic oxides/hydroxides will be presented. References Ying, Y.; Godínez-Salomón, J.F.; Moreno, A.; Lartundo-Rojas, L.; Meyer, B.; Damin, C.A.; Rhodes, C.P. Hydrous Cobalt-Iridium Oxide Two-Dimensional Nanoframes: Insights into Activity and Stability of Bimetallic Acidic Oxygen Evolution Electrocatalysts. Nanoscale Advances 2021, 3, 1976-1996. DOI: 10.1039/D0NA00912A Godínez-Salomón, F.; Albiter, L.; Alia, S.M.; Pivovar, B.S.; Camacho-Forero, L.E.; Balbuena, P.B.; 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 Catalysis 2018, 8, 10498-10520. DOI: 10.1021/acscatal.8b02171