Nano-Whiskers of Fe2O3 Coated with NiCo LDH Grown on Iron Foam Substrate for Overall Water Splitting

Abstract

Transition metal-based heterostructures have raised remarkable interest for their application in efficient water-splitting electrocatalysis. However, its application in water splitting is currently limited due to low activity and stability at high current densities. Here, we report the rational design and synthesis of a three-dimensional nano-whisker heterostructure comprising nickel cobalt layered double hydroxides (NiCoLDH) deposited on iron oxide grown on iron foam (Fe) (NiCo LDH@Fe2O3/Fe foam). This hierarchical architecture specifically addresses the intrinsic limitations of NiCo LDH, including low electronic conductivity and self-aggregation tendencies. By combining controlled thermal oxidation and electrodeposition, the resulting catalyst exhibits remarkable catalytic performance with an overpotential of only 202 mV and 96 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at current densities of 10 mA cm-2, respectively, in an alkaline electrolyte. Detailed characterization and electrochemical analyses reveal that the enhanced activity stems from synergistic interactions between Fe2O3 nano-whiskers and NiCo LDH nanosheets, which optimize electron transfer pathways and maximize active site accessibility. When implemented in an electrolytic cell, the catalyst demonstrates good operational stability, achieving an ultra-low cell voltage of 1.83 V at current densities 100 mA cm-2, respectively, for overall water splitting.