Selective Preparation of Monoclinic and Tetragonal BiVO₄with Scheelite Structure and Their Photocatalytic Properties

BiVO 4 powder with scheelite structure was obtained by hydrolyzing a nitric acid solution of Bi(NO 3 ) 3 and Na 3 VO 4 with bases (Na 2 CO 3 and NaHCO 3 ) at room temperature. Tetragonal BiVO 4 of a high-temperature form was obtained after 4.5 h of preparation time while monoclinic BiVO 4 was done after 46 h. Although the structure and the band gap of tetragonal BiVO 4 with scheelite structure were similar to those of monoclinic BiVO 4, the photocatalytic activity of the tetragonal BiVO 4 for O 2 evolution from an aqueous AgNO 3 solution under visible light irradiation was negligible. In contrast, the monoclinic BiVO 4 showed high photocatalytic activity. Distortion of a Bi−O polyhedron by a 6s 2 lone pair of Bi 3+ plays an important role for high photocatalytic activity of the monoclinic BiVO 4 under visible light irradiation.