Chloride‐Tolerant Iridium Single‐Atom Modulated Nickel Hydroxide for Industrial‐Current‐Density Seawater Electrolysis

ABSTRACT Electrocatalytic seawater electrolysis remains challenging due to chloride‐induced corrosion and impaired reaction kinetics, particularly at high current densities. Herein, single iridium atoms anchored on Ni(OH) 2 are demonstrated as an electrocatalyst for seawater electrolysis, enabling stable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance during 500 h of continuous seawater electrolysis. Experimental and theoretical analyses reveal that Ir facilitates the formation of γ‐NiOOH and Ir─O species during OER, while Cl − stabilizes reactive intermediates and accelerates Ni oxidation. On the other hand, for HER, Ir sites facilitate water dissociation and stabilize H* intermediates, whereas Cl − ions modulate the adsorption–desorption equilibrium, enhancing HER kinetics without structural degradation. Moreover, it is found that Cl − increases the density of states near the Fermi level of Ni 3d and Ir 5d orbitals, lowers the energy barriers for *H, *OH, *O, and *OOH intermediates, and promotes charge transfer across Ir─O─Ni interfaces, which could be the reason for the addressed HER and OER activity. This work provides insights into the cooperative role of Ir and Cl − ions and establishes a pathway for the design of electrocatalysts for seawater splitting.