Deeply self-reconstructing CoFe(H₃O)(PO₄)₂ to low-crystalline Fe_0.5Co_0.5OOH with Fe³⁺-O-Fe³⁺ motifs for oxygen evolution reaction

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+ (k(OER)/k(M,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.