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

In this study, phosphate FeCo(H 3 O)(PO 4 ) 2 nanosheet arrays (NAs) were synthesized using an electrochemical strategy. FeCo(H 3 O)(PO 4 ) 2 NAs as precatalyst could undergo significant self-reconstruction, including leaching of phosphate anions and electro-oxidation of Co 2+ during anodizing at the potential range of oxygen evolution reaction (OER) in 1 M KOH solution, eventually resulting in the formation of Fe 0.5 Co 0.5 OOH NAs with low crystallinity. The high content of Fe in Fe 0.5 Co 0.5 OOH NAs promoted the formation of active Fe 3+ –O–Fe 3+ motifs that increased OER occurrence. Additionally, Fe incorporation increased the ratio of the reaction rate constants of oxygen evolution to Co 3+ /Co 4+ (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 Fe 0.5 Co 0.5 OOH NAs. Fe 0.5 Co 0.5 OOH nanosheet arrays (NAs) were fabricated via electrochemical self-reconstruction of CoFe(H 3 O)(PO 4 ) 2 NAs. Benefiting from the formation of active Fe 3+ –O–Fe 3+ motifs, Fe incorporation increased the ratio of the reaction rate constants of oxygen evolution to Co 3+ /Co 4+ (k OER /k M,ox ) and enhanced the reaction order on the hydroxyl ion, Fe 0.5 Co 0.5 OOH NAs exhibited outstanding catalytic performances of oxygen evolution reaction. • Fe 0.5 Co 0.5 OOH was synthesized via self-reconstruction of CoFe(H 3 O)(PO 4 ) 2 . • High content of Fe promoted the formation of [di-μ-O(OH)] Fe 3+ –O–Fe 3+ in Fe 0.5 Co 0.5 OOH. • [di-μ-O(OH)] Fe 3+ –O–Fe 3+ motifs in oxyhdroxide acted as OER active sites. • Fe incorporation varied the electrokinetic parameters of oxyhydroxide. • [di-μ-O(OH)] Fe 3+ –O–Fe 3+ motifs further increased the reaction order on the OH - .