Synthesis, Photoluminescence and Photocatalytic Performance of BiPO4 with Different Phase Structures

Three kinds of crystal phase BiPO₄(HP, LTBP, and HTBP) were selectively synthesized by controlling the preparation conditions. Structures of the three samples are all constructed by PO₄ and BiO₈ polyhedra but with different geometric structures. Detailed characterization was carried out by X-ray diffraction(XRD), scanning eletron microscopy(SEM) and Raman, UV-Vis, and luminescence spectrometries. Three samples exhibit huge distinctions in their photoluminescence(PL) lifetime: 0.68, 162 and 160 μs for HP, LTBP, and HTBP, respectively. More interesting, an outstanding photocatalytic activity is observed for as-prepared LTBP nanorod, which shows even higher activity for the degradation of MB solution than P25. In addition, experiments were carried out to clarify the role of hydroxyl (^·OH) and superoxide radicals(O₂^·) played in photocatalytic process and it was found O₂^· was the main active species in BiPO₄ photocatalysts. Further comparison of structural and photocatalytic properties of the three samples finds that structure distortion is contributed to their property difference. A correlation was found between photocatalytic performance and the distortion of BiO₈ dodecahedra. The internal field generated by the distortion of BiO₈ dodecahedra was believed advantageous for the separation of electron and hole, which was in favor of the improvement of photocatalytic activity. This correlation may help to design other photocatalysts with high activity.