Figure 1 summarizes the materials derived from different
synthetic conditions involving the anodization of tungsten
metal and subsequent hydrothermal treatment in achieving
Bi2WO6. Flower-structured WO3·2H2O (sample A) was
obtained under unstirred conditions, while porous WO3 films
(sample B) were achieved under stirred condition introduced
during the anodization process. Flower-structured WO3
(sample C) was attained after WO3·2H2O (sample A)
experienced the loss of water molecules through calcination
at 400 °C for 4 h.17