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

• Published in: Applied catalysis. B, Environmental Environmental, 2022-05, Vol.304, p.120986, Article 120986
• Main Authors: Ye, Shenghua, Lei, Yaqi, Xu, Tingting, Zheng, Lirong, Chen, Zhida, Yang, Xiuyuan, Ren, Xiangzhong, Li, Yongliang, Zhang, Qianling, Liu, Jianhong
• Format: Article
• Language: English
• Subjects: Anions; Carbon dioxide; Cobalt; Crystal structure; Crystallinity; Electrochemistry; Evolution; Ferric ions; Hydroxyl ions; Iron; Leaching; Oxidation; Oxygen; Oxygen evolution reaction; Oxygen evolution reactions; Oxyhydroxide; Phosphate; Rate constants; Self-reconstruction
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2021.120986

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. [Display omitted] Fe0.5Co0.5OOH nanosheet arrays (NAs) were fabricated via electrochemical self-reconstruction of CoFe(H3O)(PO4)2 NAs. Benefiting from the formation of active Fe3+–O–Fe3+ motifs, 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, Fe0.5Co0.5OOH NAs exhibited outstanding catalytic performances of oxygen evolution reaction. •Fe0.5Co0.5OOH was synthesized via self-reconstruction of CoFe(H3O)(PO4)2.•High content of Fe promoted the formation of [di-μ-O(OH)] Fe3+–O–Fe3+ in Fe0.5Co0.5OOH.•[di-μ-O(OH)] Fe3+–O–Fe3+ motifs in oxyhdroxide acted as OER active sites.•Fe incorporation varied the electrokinetic parameters of oxyhydroxide.•[di-μ-O(OH)] Fe3+–O–Fe3+ motifs further increased the reaction order on the OH-.