Unveiling the role of FeOOH on catalyst evolution for advanced water oxidation

Abstract Creating economical and effective catalysts for the oxygen evolution reaction (OER) is essential for enhancing the efficiency of electrochemical water splitting. In this study, we designed a multicomponent heterogeneous interfacial catalyst, Ni(OH) 2 /NiCo(OH) 6 @FeOOH, using a simple two‐step method. In situ Raman and X‐ray photoelectron spectroscopy (XPS) measurements revealed the dynamic phase change occurring during the OER process. The FeOOH layer on Ni(OH) 2 /NiCo(OH) 6 altered the electronic structure, facilitating the emergence of the active NiOOH phase and markedly improving OER kinetics. Significantly, the Ni(OH) 2 /NiCo(OH) 6 @FeOOH 2:1 catalyst demonstrated a current density of 10 mA·cm −2 at an overpotential of merely 208 mV, accompanied by a Tafel slope of 37.72 mV·dec −1 , exhibiting exceptional stability over a duration of 100 h at 10 mA·cm −2 . Furthermore, the Ni(OH) 2 /NiCo(OH) 6 @FeOOH 2:1 (+)||Pt/C (−) electrolyzer cell showcased a remarkably low driving voltage of 1.52 V to achieve 10 mA·cm −2 , while also displaying impressive durability under alkaline conditions for over 100 h. This work enhances our understanding of the interfacial structure–activity relationship in composite catalysts, aiding the design of efficient catalysts with rapid kinetics.