In Situ Coupling Reconstruction of Cobalt–Iron Oxide on a Cobalt Phosphate Nanoarray with Interfacial Electronic Features for Highly Enhanced Water Oxidation Catalysis

Research in non-noble cobalt-related electrocatalysts to produce H₂ and O₂ by water splitting has aroused much attention because of the favorable adsorption of intermediates and low energy barriers. The design of hybrid electrocatalysts can be guided by the synergetic interface for outstanding performance. Herein, the CoFeO–CoPi@NF hybrid is prepared from cobalt ion Prussian blue analogues (CoFe–PBA) in situ grown on the Co₃(PO₄)₂·4H₂O nanograss. The annealed CoFeO–CoPi@NF exhibits favorable anodic oxygen evolution reaction (OER) activity and significant stability. The isolated CoFe₂O₄ nanocubes on CoPi easily transform into ultrathin CoFe₂O₄ nanosheets covering CoPi uniformly, forming strong coupling interfaces. The electrons transfer from CoFe₂O₄ to CoPi because of the matched band structures and Fermi levels. The resultant increased content of Co²⁺ and the red shift of the valence band maximum could facilitate the surface reconstruction to improve the OER performance. This paves the way to optimize the electronic structure and make the surface reconstruction prone in advanced OER.