Synthesis of niobium oxide nanowires by polyethylenimine as template at varying pH values

Abstract

Nb₂O₅ nanowires were synthesized by a hydrothermal method using PEI (polyethylenimine) as a soft template. The results indicated that the pH value greatly affected the Nb₂O₅ nanowires. At high pH (pH = 9), worm-like Nb₂O₅ nanomaterials were produced on account of writhing and coiling chains of PEI. In contrast, Nb₂O₅ nanowires were formed when the pH value was lower than 7, because the PEI chains extended due to electrostatic repulsion between ammonium cations. With a decrease in the pH value, the aspect ratio of Nb₂O₅ nanowires became lower, and the BET surface area increased. When the pH value reached 1–2, Nb₂O₅ nanowires had a surface area as high as 245 m² g⁻¹. In dehydrogenation of D-xylose to furfural, the catalytic Nb₂O₅ nanowires prepared at pH = 1–2 and calcined at 500 °C showed a high conversion rate and yield of 90.3% and 73.7%, respectively.