Understanding of Oxygen Redox in the Oxygen Evolution Reaction

The electron-transfer process during the oxygen evolution reaction (OER) often either proceeds solely via a metal redox chemistry (adsorbate evolution mechanism (AEM), with metal bands around the Fermi level) or an oxygen redox chemistry (lattice oxygen oxidation mechanism (LOM), with oxygen bands around the Fermi level). Unlike the AEM, the LOM involves oxygen redox chemistry instead of metal redox, which leads to the formation of a direct oxygen-oxygen (O-O) bond. As a result, such a process is able to bypass the rate-determining step, that is, O-O bonding, in AEM, which highlights the critical advantage of LOM as compared to the conventional AEM. Thus, it has been well reported that LOM-based catalysts are able to demonstrate higher OER activities as compared to AEM-based catalysts. Here, a comprehensive understanding of the oxygen redox in LOM and all documented and possible characterization techniques that can be used to identify the oxygen redox are reviewed. This review will interpret the origins of oxygen redox in the reported LOM-based electrocatalysts and the underlying science of LOM-induced surface reconstruction in transition metal oxides. Finally, perspectives on the future development of LOM electrocatalysts are also provided.

Automated summary

This article provides a comprehensive review of the oxygen redox process in the oxygen evolution reaction (OER) through lattice oxygen oxidation mechanism (LOM), and discusses the characterization techniques used to identify the oxygen redox. It explains the critical advantage and underlying science of LOM compared to the traditional adsorbate evolution mechanism (AEM) in generating higher OER activities. The article also provides insights into future developments in LOM electrocatalysts.