Most reported catalysts for water oxidation undergo in situ electrochemical tuning to form the active species for their oxygen evolution reaction (OER). In general, the in situ electrochemical transformations of non-oxide catalysts are faster than those of the corresponding oxides, and they typically display improved OER activity. Although many approaches for tuning the active surfaces of catalysts as well as investigations into their roles in the mechanism of adsorption of OER intermediates have been reported, we still have a poor understanding of the dominant active sites formed during the OER. This review highlights current progress into the in situ electrochemical tuning with non-oxide catalysts (especially chalcogenides and pnictides) and offers a comprehensive summary of approaches for the enhancement of OER activity. We describe the non-oxide catalysts that have exhibited promising OER performance with strong in situ electrochemical tuning. We also discuss the preoxidation peak positions of the catalysts in alkaline electrolytes. Furthermore, we explore the probability of new active surface formation on non-oxide catalysts with modified OER mechanisms and the collections of available in situ and ex situ methods to identify the active sites in real- time. Finally, we discuss the challenges affecting the future detection of the active sites of the most promising OER catalysts.
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