Deeply self-reconstructing CoFe(H3O)(PO4)2 to low-crystalline Fe0.5Co0.5OOH with Fe3+–O–Fe3+ motifs for oxygen evolution reaction

Abstract

In this study, phosphate FeCo(H3O)(PO4)2 nanosheet arrays (NAs) were synthesized using an electrochemical strategy. FeCo(H3O)(PO4)2 NAs as precatalyst could undergo significant self-reconstruction, including leaching of phosphate anions and electro-oxidation of Co2+ during anodizing at the potential range of oxygen evolution reaction (OER) in 1 M KOH solution, eventually resulting in the formation of Fe0.5Co0.5OOH NAs with low crystallinity. The high content of Fe in Fe0.5Co0.5OOH NAs promoted the formation of active Fe3+–O–Fe3+ motifs that increased OER occurrence. Additionally, Fe incorporation increased the ratio of the reaction rate constants of oxygen evolution to Co3+/Co4+ (kOER/kM,ox) and enhanced the reaction order on the hydroxyl ion. These factors significantly contributed to the outstanding OER catalytic performances of Fe0.5Co0.5OOH NAs.