Branched Tungsten Oxide Nanorod Arrays Synthesized by Controlled Phase Transformation for Solar Water Oxidation

摘要

Branched (NH4)(0.33)WO3 nanorods have been successfully synthesized by applying a simple hydrothermal approach with ammonium oxalate as capping agents. After annealing them in different atmospheres, the (NH4)(0.33)WO3 nanorods were converted to WO3 nanorods. Atmosphere-dependent morphology evolution and phase transformation by annealing of (NH4)(0.33)WO3 were observed. The branched WO3 nanorods produce a higher photoelectrochemical activity than the bare WO3 nanorods without branches obtained under similar conditions, and the improvement of efficiency by branched nanorods was ascribed to the better light-trapping characteristics and increase in surface area, which facilitates holes transfer at the WO3/electrolyte interface. The possible formation mechanisms of branched nanorods have been explored and the results show that the synergistic interaction between ammonium ion (NH4+) and acetate ion (-COO-) contributes to the formation of branched (NH4)(0.33)WO3 nanorods.