Synergizing high valence metal sites and amorphous/crystalline interfaces in electrochemical reconstructed CoFeOOH heterostructure enables efficient oxygen evolution reaction

Cobalt hydroxide nanosheet is among the most popular oxygen evolution reaction (OER) catalyst yet still suffers from sluggish catalytic kinetics, limited activity, and poor stability. Here, an efficient in situ electrochemical reconstructed CoFe-hydroxides derived OER electrocatalyst was reported. The introduction of Fe promoted the transformation of Co²⁺ into Co³⁺ in CoFe-hydroxides nanosheet, along with the formation of abundant amorphous/crystalline interfaces. Thanks for the retained nanosheet microstructure, high valence Co³⁺ and Fe³⁺ species, and the amorphous/crystalline heterostructure interfaces, the as-designed electrochemical reconstructed CoFeOOH nanosheet/Ni foam (CoFeOOHNS/NF) electrode delivers 100 mA·cm⁻² in alkaline at an overpotential of 275 mV and can stably electrocatalyze water oxidation for at least 35 h at 100 mA·cm⁻². Meanwhile, the alkaline full water splitting electrolyzer achieves a current density of 10 mA·cm⁻² only at 1.522 V for CoFeOOHNS/NFIIPt/C/NF, which is much lower than that of Ru/C/NFIIPt/C/NF (1.655 V@10 mA·cm⁻²). This work paves the way for in-situ synergetic modification engineering of electrochemical active components.[Figure not available: see fulltext.]