The alkaline-stable OER catalysts developed by now are very rare owing to the strong hydroxylation or dissolution of the metal centers that disintegrates the coordination environment thus leading to the formation of metal oxy/hydroxides. A huge challenge remains that the Fe-based catalysts are not able to resist the inherent oxidation-dissolution or electrochemical hydroxylation during the alkaline water oxidation process. To address the issues, we present a robust and highly efficient iron-based catalyst (Fe-cat) that exhibits a fast in-situ regeneration ability of active metal sites on electrodes through a healing mechanism. Through a suitable in situ electrodeposition synthesis strategy, the Fe-cat water oxidation catalyst can be quickly deposited on the electrode in a 1.0 M NaOH electrolyte containing iron-2,2'-bipyrimidine. After a continuous OER reaction, the deposited Fe-cat will dissolve rapidly into the electrolyte as soluble Fe species for the next deposition of Fe-cat and water oxidation reaction at the open circuit potential. The electrochemical and in-situ UV-vis and EPR studies suggested that the developed dynamic healing feature plays a crucial role in keeping the Fe-cat catalyst highly active and alkaline-stable. This catalyst demonstrates long-term catalytic activity with a low overpotential of 320 mV at 1.0 mA cm<sup>-2</sup> over 200 hours in 1.0 M NaOH. This is the first example of the ligand-induced active site regeneration of iron-based catalyst that presents robust features for water oxidation even at 5.0 M NaOH. We believe that this work opens a new avenue in designing new catalysts with ligand-induced active site in-situ regeneration feature to resist complete electrochemical hydroxylation and dissolution.

Regenerable catalyst for highly alkaline water oxidation

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