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

Bismuth molybdate films with various phase structures including α-Bi2Mo3O12, β-Bi2Mo2O9, γ-Bi2MoO6, and γ′-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. α-Bi2Mo3O12, β-Bi2Mo2O9, and γ-Bi2MoO6 film can be obtained at 400 °C, 500 °C, and 500 °C for 1 h, respectively. At 500 °C, γ′-Bi2MoO6 can be obtained for 4 h. Film formation process is proposed based on the experimental results. Thin γ-Bi2MoO6 films exhibit high photoresponse under visible light irradiation. Incident photon to current conversion efficiency of thin γ-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, γ′-Bi2MoO6 generated weak photocurrent; α-Bi2Mo3O12 and β-Bi2Mo2O9 film has no photoresponse under visible light irradiation. The reason for the difference in the visible light response was discussed.