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DOE OSTI2023

Synergistic Co-Ir/Ru Composite Electrocatalysts Impart Efficient and Durable Oxygen Evolution Catalysis in Acid

Exploring highly active and robust catalysts, which have low precious metal content, to boost the kinetically sluggish oxygen evolution reaction (OER) is a key concern for hydrogen production via proton exchange membrane water electrolysis (PEMWE). Here, in this work, rational engineering of the morphology and the local geometric ligand environment of Ir and Ru catalysts are presented by using defect-rich, lanthanum- and lithium-doped Co 3 O 4 nanofiber (LLCF) as substrate that promotes the electrocatalytic OER. Two catalysts, IrCoOx@LLCF and RuCoOx@LLCF, achieve mass activities of 1013.5 A g Ir –1 and 1911.4 A g Ru –1 in 0.1 M HClO 4 at 300 mV overpotential, respectively, which are 26 and 50 times higher than that of commercial IrO 2 and RuO 2 . Operando X-ray absorption spectroscopy unveils the reversible structure of IrCoOx during the OER and the suppression of over-oxidation of Co and Ir, giving rise to high stability. Density functional theory calculations reveal that the local geometric ligand engineering optimizes the binding of oxygenated species to the active sites, resulting in strongly enhanced catalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Materials Data on Co3Ir by Materials Project

IrCo3 is beta-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ir is bonded to six equivalent Ir and six equivalent Co atoms to form IrCo6Ir6 cuboctahedra that share corners with six equivalent IrCo6Ir6 cuboctahedra, corners with twelve equivalent CoCo12 cuboctahedra, edges with six equivalent IrCo6Ir6 cuboctahedra, edges with twelve equivalent CoCo9Ir3 cuboctahedra, faces with six equivalent IrCo6Ir6 cuboctahedra, and faces with fourteen CoCo12 cuboctahedra. All Ir–Ir bond lengths are 2.62 Å. All Ir–Co bond lengths are 2.61 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to twelve Co atoms to form CoCo12 cuboctahedra that share corners with six equivalent CoCo12 cuboctahedra, corners with twelve equivalent IrCo6Ir6 cuboctahedra, edges with eighteen CoCo12 cuboctahedra, faces with two equivalent IrCo6Ir6 cuboctahedra, and faces with eighteen CoCo12 cuboctahedra. There are six shorter (2.47 Å) and six longer (2.62 Å) Co–Co bond lengths. In the second Co site, Co is bonded to three equivalent Ir and nine Co atoms to form distorted CoCo9Ir3 cuboctahedra that share corners with eighteen equivalent CoCo9Ir3 cuboctahedra, edges with six equivalent IrCo6Ir6 cuboctahedra, edges with twelve CoCo12 cuboctahedra, faces with six equivalent IrCo6Ir6 cuboctahedra, and faces with fourteen CoCo12 cuboctahedra. All Co–Co bond lengths are 2.62 Å.

36 MATERIALS SCIENCE↗