Microwave-assisted evolution of WO3 and WS2/WO3 hierarchical nanotrees

Abstract

Although branched WO₃ nanostructures have been investigated for electrochromic devices and catalytic electrodes, a detailed study on their structural evolution mechanism has rarely been carried out. In this work, we have demonstrated the microwave-assisted synthesis of branched WO₃ nanotrees consisting of [001]-oriented WO₃ needle-like structures growing radially from the surface of WO₃ nanohelixes. The mechanism for the evolution of WO₃ nanotrees with the preferred orientation was systematically investigated in terms of the reaction temperature and the distribution of the electric field applied by microwave irradiation. In addition, it was shown that the WO₃ nanotrees can be easily converted into WS₂/WO₃ hierarchical nanotrees by a simple sulfurization process, and used as an efficient catalytic electrode for the hydrogen evolution reaction.