In situ generation of FeOOH/NiOOH interface in FeS2/NiS2 nanosheets through deep reconstruction for efficient oxygen evolution reaction

Transition metal sulfides (TMSs) for electrochemical water splitting undergo significant self-reconstruction to form actual active species favorable for high oxygen evolution reaction (OER) performance. However, the complete self-reconstruction of most reported TMSs in alkaline media is unfrequent and the active species cannot be efficiently used. Herein, self-supported FeS2/NiS2 nanosheet arrays (FeNiS) are deliberately fabricated as pre-catalysts and then accomplished deep phase transformation into low-crystalline and ultrathin FeOOH/NiOOH (FeNiS-R) nanosheets favorable to alkaline OER. Various ex situ characterization studies uncover that the FeNiS-R with abundant interfaces is generated via complete reconstruction during electrolysis and the high-valence Fe and Ni in the FeNiS-R interface are the real active sites for high OER activity. The reconstructed FeNiS-R exhibits a small overpotential of 290 mV at 100 mA cm(-2) and favorable durability (>= 80 h), much superior to commercial benchmark IrO2. This work provides a promising avenue to achieve the deep reconstruction of TMSs and the targeted design of OER catalysts in energy devices.