Facile construction of hierarchical Co3S4/CeO2 heterogeneous nanorod array on cobalt foam for electrocatalytic overall water splitting

Abstract

Herein, a hierarchical Co₃S₄/CeO₂ nanorod array on cobalt foam (Co₃S₄/CeO₂-CF) was successfully constructed via a facile one-step hydrothermal method. The fabrication of Co₃S₄/CeO₂-CF was confirmed by X-ray diffraction, scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM). It is observed that CeO₂ nanorod was fully covered with Co₃S₄ nanosheets, forming a hierarchical core-shell nanostructure. Furthermore, CeO₂ and Co₃S₄ were doped with each other during the one-step hydrothermal process, forming a heterogeneous Co₃S₄/CeO₂ nanostructure. Density functional theory (DFT) calculations suggest that the introduction of CeO₂ in Co₃S₄ is effective in reducing the free energy barrier of OER process. To achieve current density of 10 mA cm^-2, only small overpotentials of 74.9 mV and 213 mV are required for HER and OER in 1.0 M KOH solution, respectively. In particular, the Co₃S₄/CeO₂-CF based electrolysis cell for overall water splitting only needs an output voltage of 1.64 V in the alkaline medium, lower than that of Pt/C-RuO₂-based electrolysis cells (1.70 V). Such hierarchical heterogeneous catalyst also shows ultra-stable catalytic activity. Therefore, with the favorable heterointerfaces and hierarchical structures, Co₃S₄/CeO₂-CF could be a promising bifunctional electrocatalyst for overall water splitting and this study may also provide a facile method for the preparation of hierarchical heterogeneous nanostructured materials.

Keywords: Heterogeneous nanostructure; Hierarchical Co(3)S(4)/CeO(2) nanorod array; Hydrogen evolution reaction; Overall water splitting; Oxygen evolution reaction.