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

Abstract

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.