Construction of Bi₂MoO₆/Ag₂CrO₄ Heterojunction Nanocomposites with Enhanced Visible-Light Photocatalytic Activity and...

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.