Strong Lewis acid-induced self-healing of loose FeOOH for alkaline oxygen evolution

The fast leaching of the Fe catalytic center and low conductivity of FeOOH have hindered the optimal stability and activity of Fe-based electrocatalysts for oxygen evolution reactions (OER). Here, Zn2+ is introduced into FeOOH with a looser nanosheet structure by regulating electric double layer (EDL) repulsion during electrodeposition. Meanwhile, as strong Lewis acids, Zn2+ in ZnxFeOOH could act as an electron acceptor, accepting electrons from FeOOH. The doping of Zn2+ shortens the bond length of Fe-O and enhances the covalency of Fe-O to improve electron transport rate and stability. The faster catalytic kinetics also been obtained by facilitating O* to form OOH* intermediates. At 100 mA cm−2, Zn0.5FeOOH requires overpotential of only 250 mV and maintains initial activity in 1 M KOH after 120 h. Notably, Zn-induced self-healing is achieved when the leaching and redeposition of Fe reach dynamic equilibrium. In 1 M KOH seawater, Zn0.5FeOOH requires overpotentials of 286 mV to produce current density of 100 mA cm−2. At 2.0 V, Zn0.5FeOOH can achieve 1000 mA cm−2 in anion exchange membrane (AEM) water electrolyzer at room temperature. This work provides an effective Zn-induced strategy for designing efficient and stable OER catalysts for industrial development.