Synthesis and photoelectrochemical properties of thin bismuth molybdates film with various crystal phases

Bismuth molybdate films with various phase structures including alpha-Bi2Mo3O12, beta-Bi2Mo2O9, gamma-Bi2MoO6, and gamma'-Bi2MoO6 are fabricated on the indium-tin oxide glass substrates from an amorphous heteronuclear complex via the dip-coating method by appropriate adjustment of the reaction conditions. alpha-Bi2Mo3O12, beta-Bi2Mo2O9, and gamma-Bi2MoO6 film can be obtained at 400 degrees C, 500 degrees C, and 500 degrees C for 1 h, respectively. At 500 degrees C, gamma'-Bi2MoO6 can be obtained for 4 h. Film formation process is proposed based on the experimental results. Thin gamma'-Bi2MoO6 films exhibit high photoresponse under visible light irradiation. incident photon to current conversion efficiency of thin gamma'-Bi2MoO6 film starts to increase near 450 nm. And, it can reach 4.1% at 400 nm. The top of the valence band and bottom of the conduction band are roughly estimated to be -0.71 and 1.69 ev, respectively. In contrast, gamma'-Bi2MoO6 generated weak photocurrent; alpha-Bi2Mo3O12 and beta-Bi2Mo2O9 film has no photoresponse under visible light irradiation. The reason for the difference in the visible light response was discussed. (C) 2009 Published by Elsevier B.V.