Lattice Oxygen Mechanism Induced on Nickel Sites by Cl^- Adsorption for Efficient Seawater Oxidation Reaction

Efficient seawater oxidation reaction is crucial for advancing hydrogen fuel production. Developing highly efficient oxygen evolution reaction (OER) catalysts that follow the lattice oxygen mechanism (LOM) can effectively mitigate undesirable chloride oxidation side reactions in seawater electrolysis and reduce energy consumption. Herein, we propose a Cl^--mediation strategy that is able to shift the OER mechanism from the adsorbate evolution mechanism (AEM) to LOM on nickel sites. By loading highly dispersed Ir onto Ni-based precursors (e.g., NiSe, Ni(OH)₂, NiS₂ and NiSOH), we exploit the robust coordination interaction between Ir and Cl^- in seawater to establish a Cl-Ir-O-Ni electron-withdrawing chain from Ni to Cl, which strengthens Ni-O covalency in situ during the OER, thereby activating lattice oxygen around the Ni sites in seawater. As a result, the Cl-modified Ir/NiOOH-Se@Cl catalyst requires an overpotential of only 313 mV to achieve an OER current density of 0.5 A cm^-2, demonstrating a reduction of 147 mV compared to that in alkaline condition (Ir/NiOOH-Se@OH) and also maintaining stable operation at 0.5 A cm^-2 for 500 h. Our work provides a novel and intriguing concept for regulating local lattice oxygen activity toward developing highly efficient oxygen electrocatalysts for clean energy productions.