Facile construction of hierarchical CoS/CeO heterogeneous nanorod array on cobalt foam for electrocatalytic overall water splitting.

Herein, a hierarchical CoS/CeO nanorod array on cobalt foam (CoS/CeO-CF) was successfully constructed via a facile one-step hydrothermal method. The fabrication of CoS/CeO-CF was confirmed by X-ray diffraction, scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM). It is observed that CeO nanorod was fully covered with CoS nanosheets, forming a hierarchical core-shell nanostructure. Furthermore, CeO and CoS were doped with each other during the one-step hydrothermal process, forming a heterogeneous CoS/CeO nanostructure. Density functional theory (DFT) calculations suggest that the introduction of CeO in CoS is effective in reducing the free energy barrier of OER process. To achieve current density of 10 mA cm, 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 CoS/CeO-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-RuO-based electrolysis cells (1.70 V). Such hierarchical heterogeneous catalyst also shows ultra-stable catalytic activity. Therefore, with the favorable heterointerfaces and hierarchical structures, CoS/CeO-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.