Oriented and robust anchoring of Fe via anodic interfacial coordination assembly on ultrathin Co hydroxides for efficient water oxidation

Abstract

The oriented distribution and strong bonding of Fe active sites in multiple metal hydroxides are crucial to modulate activity and stability for efficient oxygen evolution reaction (OER). However, the dispersion and inevitable dissolution of Fe species still need to be addressed through deliberate design. Here, trace amounts of Fe chelated with tannic acid (TA) are precisely anchored to ultrathin Co hydroxides (TF@Co(OH)₂-t) through a new anodic interfacial coordination assembly strategy: firstly, the ZIF-67@Co(OH)₂ precursor with ultrathin Co(OH)₂ nanosheets vertically grown on the shell, provides abundant active sites and sufficient anchoring regions for subsequent TA–Fe coating; secondly, the TA–Fe ligand network quickly and robustly coats the surface of the Co(OH)₂via positive potential-driven chronopotentiometry, yielding TF@Co(OH)₂-t with good dispersion and controllable Fe species. The TA–Fe network efficiently activates Co species and prevents the dissolution of Fe ions. Physical characterization and DFT simulations reveal that the optimized OER activity with 317 mV at 10 mA cm⁻² for TF@Co(OH)₂-500 can be attributed to the accelerated electron transfer, increased active sites, and the moderate fall in d-band center levels due to Fe integration. Moreover, prolonged stability is realized benefiting from the robust TA–Fe coating protecting the actives sites.