As electrocatalysts with low overpotential and self-healing properties, cobalt oxide films have garnered much attention as promising components in water splitting technologies. However, insight into charge transport kinetics in the films have proved difficult, with electrochemical studies suggesting that slow charge transport presents a practical challenge for thicker catalytic films. Here UV-Vis spectroelectrochemistry and transient absorption spectroelectrochemistry are used to ascertain potential dependent and thickness dependent properties of spectrally observable hole populations in both phosphate cobalt oxide and borate cobalt oxide films. We show that absorption spectroscopy exclusively probes the hole dynamics and reports on bulk electron transport within the films. Furthermore, the primary role of the electrochemical potential is to increase the effective concentration of holes that go on to enable oxygen evolution reactivity.

Exploring hole dynamics in oxygen-evolving cobalt oxide films

ACS Spring 2022

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