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Updated: May 15, 2025

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing
Published on: June 9, 2023
Quantifying Dynamic Changes of Oxygen Nonstoichiometry and Formation of Surface Phases of SrCoO Electrocatalysts by
Yang Hu1,2,3, Luhan Wei2, Haowen Chen2
1Zhejiang University, Hangzhou, Zhejiang 310027, China.
Abstract:
Perovskite electrocatalysts like strontium cobaltite (SrCoO, denoted as SCO) experience dynamic changes in both surface and bulk during the oxygen evolution reaction (OER), rather than remaining static. This dynamic, electrochemically driven evolution in composition, structure, and ionic defects (e.g., oxygen vacancies) can strongly impact the OER activity and stability. Yet, the current lack of quantitative information on these processes impedes a precise and predictive evaluation of the individual and combined effect of both bulk and surface transformations. Here, using epitaxial SCO thin films as a model system, we demonstrate that SCO is a bulk and surface redox-active OER electrocatalyst that undergoes a bulk phase transition via electrochemically induced oxygen intercalation, as well as a surface phase transition toward Co (oxy-)hydroxide. Specifically, applying a suite of operando and ex situ characterization we established a reliable relationship between oxygen nonstoichiometry, optical density, and conductivity as a function of applied potentials. We further accurately quantify the evolution of oxygen stoichiometry in the SCO bulk and the thickness of the formed surface secondary phase. Our work provides a reliable and generalizable workflow and operando characterization toolbox for quantitative assessment of surface and bulk transformations in oxygen-deficient perovskite electrocatalysts.
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