Hydrothermal temperature-driven evolution of morphology and electrocatalytic properties of hierarchical nanostructured CoFe-LDHs as highly efficient electrocatalysts for oxygen evolution reactions

Abstract

The development of economical and efficient oxygen evolution reaction (OER) catalysts plays an important part in electrochemical water oxidation, and it has been known that the electrocatalytic performance of these materials is closely related to their micromorphology at micro/nanometer scales. Herein, we report a unique hierarchical nanosheet–nanowire structure of a CoFe layered double hydroxide (LDH) electrocatalyst directly grown on conductive nickel foam (NF) by optimizing the hydrothermal temperature of the reaction. The hydrothermal temperature is decisive in driving the formation of the wire-in-sheet morphology of CoFe-LDH, while the hydrothermal time has almost no effect on the morphology of the electrocatalyst. The possible mechanism of the morphological evolution has been proposed. The wire-in-sheet nanoarray of CoFe-LDH provides a higher number of active sites, more intricate transmission networks and improved electronic conductivity, resulting in enhanced electrocatalytic performance. Consequently, the resultant CoFe-LDH exhibits superior OER performance: a low overpotential of 242 mV at 100 mA cm⁻² (η = 242 mV@100 mA cm⁻²), with an exceedingly small Tafel slope of 41 mV dec⁻¹, as well as an ultra-long durability (97 h) in 1 M KOH electrolyte. Therefore, the design of a unique hierarchical nanostructure by tuning the reaction conditions may open up a new avenue for high-performance OER electrocatalysts.