Hierarchical Ni/Ni(OH)₂‑NiCo₂O₄ Supported on Ni Foam as Efficient Bifunctional\nElectrocatalysts for Water Splitting

Abstract

Developing efficient and cost-effective\nbifunctional catalytic\nelectrodes is of great importance to water splitting. In this study,\nhybrid Ni/Ni­(OH)₂-coated NiCo₂O₄ nanorods\nwere grown on Ni foam (NF) by a facile growth–conversion–epitaxy\napproach. The epitaxial decoration of Ni/Ni­(OH)₂ composite\ncould increase the intrinsic activity of NiCo₂O₄/NF and enhance the charge-transfer rate. This self-standing hierarchical\nnanohybrid with unique surface chemistry and interface engineering\nexhibits an excellent electrocatalytic performance. The optimized\nNi/Ni­(OH)₂-NiCo₂O₄/NF only requires\noverpotentials of 53 and 235 mV to reach a current density of 10 mA\ncm^–2 for HER and OER, respectively. The electrolyzer\nachieved 10 mA cm^–2 at a low cell voltage of 1.51\nV for water splitting. This work offers a new perspective for rationally\ndesigning electrocatalytic materials by surface decoration.