Hemin Molecular Catalyst with Axial Cl-Fe Coordination for Selective and Stable Acidic Chlorine Evolution

The chlorine evolution reaction (CER) is essential for industrial chlorine production. However, achieving high CER selectivity remains a challenge due to the high cost and narrow potential gap between the CER and the competing oxygen evolution reaction (OER) in conventional noble oxide catalysts. In this work, Hemin is adopted as a model molecular catalyst for CER owing to its porphyrin macrocycle and the axial Cl ligand, achieving an overpotential of ∼190 mV at 10 mA cm^-2 with ∼100% chlorine selectivity and excellent stability over 100 h in corrosive acidic brine. Spectroscopic and electrochemical analyses reveal that the axial Cl-Fe interaction stabilizes the rigid configuration geometry of the Hemin molecule, while the π-conjugated macrocycle and the Fe-centered electronic effect jointly modulate the electronic state of Fe. This combination effectively suppresses electrochemical demetalation and preserves structural integrity for enhancing selectivity and durability. It is hoped that this work can propose fundamental insight into the rational design of efficient molecular electrocatalysts for promoted chlorine evolution.