The Role of Cu+3 in Oxygen Evolution Activity of Copper-Oxides

Published

May 1, 2025

Author(s)

Pooja Basera, Yang Zhao, Angel Garcia-Esparza, Finn Babbe, Neha Bothra, John Vinson, Dimosthenis Sokaras, Junko Yano, Shannon Boettcher, Michal Bajdich

Abstract

Cu-based oxides and hydroxides represent an important class of materials from a catalytic and corrosion perspective. In this study, we investigate the formation of bulk and surface Cu+3 species stable under water oxidation catalysis in alkaline media. So far, no direct evidence existed for the presence of hydroxides (CuOOH) or oxides, which were primarily proposed by theory. This work directly places CuOOH in the oxygen evolution reaction (OER) Pourbaix stability region with a calculated free energy of -208.68 kJ/mol, necessitating a revision of known Cu-H2O phase diagrams. We also predict that the active sites of CuOOH for the OER are consistent with a bridge O* site between the two Cu+3 atoms with onset at ≥1.6 V vs. the reversible hydrogen electrode (RHE), aligning with experimentally observed Cu+2/+3 oxidation waves in cyclic voltammetry of Fe-free and Fe-spiked copper in alkaline media. Trace amount of Fe (2 µg/mL (ppm) to 5 µg/mL) in the solution measurably enhances OER catalytic activity, likely due to the absorption of Fe species that serve as OER surface active sites. Importantly, near-surface sensitive modulation excitation X-ray absorption spectroscopy of a Cu thin-film electrode shows distinct Cu+3 fingerprint under OER conditions at 1.8 V vs. RHE. Additionally, in-situ Raman spectroscopy of polycrystalline Cu in 0.1 mol/L (M) KOH revealed features consistent with those calculated for CuOOH in addition to CuO. Overall, this work provides direct evidence of bulk electrochemical Cu+3 species under OER conditions and expands our longstanding understanding of the oxidation mechanism and catalytic activity of copper.

Citation

Journal of the American Chemical Society

Volume

147

Pub Type

Journals

Download Paper

https://doi.org/10.1021/jacs.4c18147

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Citation

Basera, P. , Zhao, Y. , Garcia-Esparza, A. , Babbe, F. , Bothra, N. , Vinson, J. , Sokaras, D. , Yano, J. , Boettcher, S. and Bajdich, M. (2025), The Role of Cu+3 in Oxygen Evolution Activity of Copper-Oxides, Journal of the American Chemical Society, [online], https://doi.org/10.1021/jacs.4c18147, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959421 (Accessed October 8, 2025)