Porous NiCo2S4/FeOOH nanowire arrays with rich sulfide/hydroxide interfaces enable high OER activity

Interface engineering has been recognized as a highly effective strategy for improving the intrinsic activity of catalysts for oxygen evolution reaction (OER), wherein the rational construction of interfacial nanostructures has been the key to promote the sluggish OER kinetics. Herein, self-supported NiCo2S4/FeOOH nanowire arrays with rich heterointerfaces being embedded in were constructed via a two-step route, namely, hydrothermal synthesis of hydroxide precursors and then selective sulfur anion exchange, which was purposely realized by utilizing the different solubility product constants (Ksp) of Ni(II), Co(II), and Fe(III)-hydroxides and controlling the sulfidation conditions. The as-synthesized NiCo2S4/FeOOH nanowire arrays as a pre-catalyst present a large length-diameter ratio and porous feature, which is beneficial to expose high density of active sites and accelerate the mass transport. In addition, the synergy arising from interfacial electron redistribution and multiple active sites substantially helps optimize the surface binding energy of the different intermediates as demonstrated by our experimental investigations and theoretical calculations, thus enabling the remarkable overall activity for OER with an ultra-low overpotential of ~200 mV to deliver the current density of 10 mA cm−2. This interface engineering strategy can be expanded to advance other interfacial structures, which is believed to afford inspiration in the field of interface engineering for high-performance catalysts.