Weijie Hua, Songhua Huang, Huixin Yuan
In this work, flower-like Bi2MoO6 microspheres were first prepared by solvothermal synthesis. Ag2CrO4 nanoparticles were then deposited in situ onto the Bi2MoO6 surface, leading to the formation of a Bi2MoO6/Ag2CrO4 n-n heterojunction nanocomposite photocatalyst. Through characterization technologies and visible-light degradation experiments, the photocatalytic behavior and degradation mechanisms of nanocomposites were explored. The results demonstrated that Ag2CrO4 block-like particles were uniformly anchored onto the surface of the flower-like Bi2MoO6 microspheres. The diffraction peaks, lattice fringes, XPS binding energies and FT-IR absorption bands of the composite samples were in good agreement with those of the individual components. Construction of the heterojunction remarkably broadened the optical response of Bi2MoO6, extending the absorption edge from 497 to 713 nm. The band gap decreased to 1.52 eV, lower than the values measured for either constituent semiconductor. Moreover, the nanocomposite showed a markedly lower photoluminescence emission intensity. The Bi2MoO6/Ag2CrO4 photocatalyst removed maximum 99.43% of Rhodamine B (RhB) within 60 min under visible-light illumination. The photocatalytic activity of nanocomposite with a Bi2MoO6:Ag2CrO4 molar ratio of 1:1 was 3.56 times that of pure Bi2MoO6, while the kinetic constant reached 0.0570 min-1, exceeding those of Bi2MoO6 and Ag2CrO4 by factors of 13.90 and 2.26, respectively. After five consecutive reuse cycles, the photocatalyst still removed more than 85% of RhB from aqueous solution. Optimal degradation performance was obtained using 0.50 g/L of photocatalyst and the initial RhB concentration of 10 mg/L. The photocatalytically generated active species h+ and ·O2- can effectively decompose the chromophores of RhB molecules in water. Finally, the degradation mechanism of RhB by nanocomposites was proposed.