Operando spectroscopies capturing surface reconstruction and interfacial electronic regulation by FeOOH@Fe₂O₃@Ni(OH)₂...

Developing high-performance and low-cost electrocatalysts for oxygen evolution reaction (OER) and understanding the phase evolution in the catalytic process are vital to improving the overall efficiency of electrochemical water splitting. Herein, a hybrid heterogeneous FeOOH@Fe₂O₃@Ni(OH)₂ electrocatalyst with robust OER intrinsic activity and a low overpotential of 269 mV to obtain a current density of 100 mA cm^-2 and a Tafel slope value of 60.15 mV dec^-1 is effectively prepared. The dynamic surface evolution has been detected by in-situ Raman spectroscopy, which exposes that FeOOH@Fe₂O₃@Ni(OH)₂ is reconstituted as Ni(Fe)OOH demonstrated as catalytically active species under high potential. X-ray photoelectron spectroscopy analysis indicates that partial electrons of Ni in the heterogeneous interface transfer to Fe. Furthermore, partial Fe doping of NiOOH under high potential accompanied by the oxidized Ni³⁺ with optimized d-orbit electronic configuration for nearly unity e_g occupancy results in proper chemisorption bonding strength for oxygen reaction intermediates and is conducive to enhancing OER reaction kinetics. This work provides ideas that multicomponent heterostructure can adjust the electronic structure of iron and nickel to enhance the intrinsic activity of OER, which could help with the design and synthesis of high-performance OER catalysts used in energy storage and conversion.