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

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 m(2) g(-1) . In dehydrogenation of D-xylose to furfural, the catalytic Nb2O5 nanowires prepared at pH = 1-2 and calcined at 500 degrees C showed a high conversion rate and yield of 90.3% and 73.7%, respectively.