fig1

Figure 1. Structural characterizations. (A) Schematic illustration for the formation of mesoporous Nb₂O₅ microspheres; (B and C) SEM images with different magnifications and TEM image (Inset) of the as-made Nb₂O₅ microspheres; (D and E) SEM images, (F) TEM image, (G) HRTEM image and (H) corresponding SAED pattern of the mesoporous Nb₂O₅ microsphere after calcination in air. SEM: Scanning electron microscopy; TEM: transmission electron microscopy; HRTEM: high-resolution TEM; SAED: selected area electron diffraction.