Bi5Nb3O15 as a photocatalyst:: photocatalytic and photoelectrochemical studies

Bi5Nb3O15 was prepared from a stoichiometric mixture of Bi2O3 and Nb2O5 at 300-500 degrees C. The prepared photocatalyst was characterized by diffuse reflection spectrum (DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle size analysis. The band gap, crystal structure and average grain size were determined from the above methods to be 3.25 eV, distorted pyrochlore and 4-5 mu m respectively. The photoelectrochemical behavior of hydrogen-reduced Bi5Nb3O15 was investigated in 0.1 M Na2SO4 and using the Fe(CN)(6)(3-/4-) redox couple for measuring the current-voltage characteristics. The cyclic voltammetric studies revealed that the onset potential for photocurrent generation existed at -0.45 V, which is more negative to water reduction level at pH 7.0, and that of the photocurrent at 1.0 V was observed as 0.58 mA/cm(2). Photocatalytic hydrogen production has been achieved by using Bi5Nb3O15 as a photocatalyst in presence of methyl viologen. The quantum yield for hydrogen production for this system was found to be 0.83. All the studies clearly indicated that Bi5Nb3O15 has potential in solar energy conversion.