Facile synthesis of ultrathin two-dimensional nanosheets-constructed MCo2O4 (M = Ni, Cu, Zn) nanotubes for efficient photocatalytic oxygen evolution

Abstract

Hierarchical nanosheets-assembled nanotubes are of great interest for their unique physicochemical properties as well as their potential applications in a variety of fields. However, the synthesis of hierarchical mixed transition-metal oxides-based nanosheets-assembled nanotubes for highly efficient photocatalytic oxygen evolution is rarely reported. Herein, a simple and versatile approach was developed to synthesize hierarchical nanosheets-constructed MCo₂O₄ (M = Ni, Cu, Zn) nanotubes. Core–shell polyacrylonitrile (PAN)/M-cobalt hydroxide ultrathin nanosheet composite nanofibers were first synthesized by hydroxylation reaction between PAN/M-cobalt acetate hydroxide precursors and NaBH₄. After calcination, these nanofibers as precursors were easily transformed into the corresponding hierarchical nanosheets-constructed MCo₂O₄ nanotubes. By applying a photocatalyst, the resultant MCo₂O₄ nanotubes, particularly the CuCo₂O₄ nanotubes, exhibited high photocatalytic activity and cycle stability toward water oxidation reaction with O₂ generation rates of 51.1 mmol g⁻¹ h⁻¹ under visible light irradiation, which is higher than most reported catalysts. This approach is very versatile and can be applied to synthesize other hierarchical multi-element oxides-based nanosheets-constructed nanotubes for advanced applications.