Reconstruction Optimization of Distorted Feooh/Ni Hydroxide for Enhanced Oxygen Evolution Reaction

Oxygen evolution reaction (OER) is one of the important anodic reactions in most of widely used electrochemical conversion devices . However, the four-electron transfer process in OER makes the reaction sluggish and reduces the efficiency accordingly. Although a lot of OER electrocatalysts have been developed, the actual active sites after the surface reconstruction during OER, which play crucial role in the catalytic performance, have not been fully understood. Herein, we find that the distorted FeOOH/Ni hydroxide on Ni foam (NF) (d-FeOOH/Ni hydroxide-NF) shows better electrochemical performance than crystalline FeOOH/Ni hydroxide-NF (c-FeOOH/Ni hydroxide-NF) because the interfaces in d-FeOOH/Ni hydroxide-NF, which are the key active sites for OER, are well maintained during the reaction compared with c-FeOOH/Ni hydroxide-NF, leading to promoted catalytic performance and long-term stability at high current density. By using in-situ and ex-situ techniques, we show that the structure rearrangement in electrocatalyst results in small crystal size and high Lewis acidity of Fe and Ni atoms in d-FeOOH/Ni hydroxide-NF, which endows high flexibility of the lattice and tolerates the volume expansion during OER greatly. Therefore, the well-maintained FeOOH/Ni hydroxide interface promotes the OER with excellent electrochemical performance (an overpotential of 1.50 V at 100 mA cm -2 and long-term durability for 32 hours at 425 mA cm -2 ), which outperforms most of the state-of-the art electrocatalysts. Our study may provide an insightful understanding on the catalytic performance of Fe-Ni based electrocatalysts and guidance for their design and synthesis for practical application