Dynamic-Coupling Axial Chloride on Dual-Heteroatom Sites for Highly Anti-Chloride Oxygen Reduction in Seawater.

Seawater electrocatalytic oxygen reduction reaction (ORR) offers a sustainable and cost-effective route for energy conversion while alleviating freshwater scarcity, but suffers from chloride (Cl-) poisoning and corrosion of metal active sites. Herein, we present a dynamic axial Cl coordination strategy to mitigate this issue, realized by precisely engineered O-bridged dual-heteroatom catalysts (FeMn DHACs) for ultrahigh electrochemical ORR activity in seawater. In situ spectroscopy combined with multiscale simulations reveal that one Cl atom dynamically is adsorbed on the Fe site forming a Cl-FeN3-O1-MnN3 active structure, which drives the Fe center from D4h to a C4v symmetry and then facilitates *OH dissociation for fast four-electron ORR kinetics. Meanwhile, Mn regulators tailor the adsorption behavior of Cl- at Fe sites, suppressing Fe corrosion and enhancing stability. Consequently, this well-designed FeMn DHACs exhibits satisfactory seawater ORR activity with a half-wave potential of 0.941 V versus RHE and a maximum power density of 179.8 mW cm-2 in a Zn-air battery. Remarkably, it delivers a negligible degradation (only 10 mV loss) after 30,000 cycles. This enhancement effect is generalizable to other M─Mn (M═Co, Ni, Cu) diatomic systems, demonstrating that Mn sites universally promote the seawater-based ORR route by regulating Cl- adsorption.