Phosphate‑Induced In Situ Co 3+ Enrichment and Hollowing of CoFe Prussian Blue Analogues at Room Temperature for Superior OER

Abstract Traditional Prussian Blue Analogues (PBAs) activation relies on high‐temperature heat treatment or multi‐step heterostructure construction, which can easily lead to skeleton collapse and active site burial. To address this issue, this work proposes a one‐step room‐temperature ion synergistic regulation strategy assisted by (NH 4 ) 2 HPO 4 (DAP), which constructs a phosphate/ammonium co‐doped CoFe‐PBA catalyst (CoFe‐PBA‐DAP) through mild ion exchange and surface coordination, achieving synergistic optimization of structure, electronic structure, and local ion environment. Room‐temperature regulation induces the formation of hollow structures and induces electron redistribution through M─O─PO n x− coordination. Combined with Co Fe bimetallic electron coupling, the electronic structure of the entire skeleton is reconstructed. In situ Raman spectroscopy indicates that co‐doping accelerates the generation of the CoOOH active phase and interfacial charge transfer during the oxygen evolution reaction (OER). Density functional theory calculations show that phosphate ions induce electronic restructuring of CoFe‐PBA through M─O─PO n x− coordination, shifting the center of the Co/Fe d‐band toward the Fermi level, enhancing H 2 O and OH − adsorption, and reducing the * OH formation energy barrier, making it thermodynamically more favorable for OER. Compared with traditional high‐temperature strategies, this work achieves equivalent electronic control through room‐temperature chemical coordination, which is more environmentally friendly and convenient.