Synthesis of Bi₂MoO₆/Bi₂Ti₂O₇ Z-Scheme Heterojunction as Efficient Visible-Light Photocatalyst for the Glycolic Acid Degradation

A novel Bi₂MoO₆/Bi₂Ti₂O₇ heterojunction photocatalyst was firstly prepared by a simple solvothermal route. The as-synthesized photocatalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectra. The effect of the material ratio, solution pH, and the salinity on glycolic acid degradation were discussed. The Bi₂MoO₆/Bi₂Ti₂O₇ (2:1) nanocomposite exhibits highest photocatalytic performance and chemical stability. The glycolic acid degradation efficiency can reach 99.9% at pH 4 after 150 min irradiation under visible light. The enhanced photocatalytic activity can be ascribed to the heterojunction interface in the composite, which is beneficial to the efficient charge carriers transfer. The degradation conforms to the pseudo-first-order kinetics. According to the oxidation species trapping experiments, the ^·O₂ ⁻, h ⁺ and ^·OH are found to play important roles in the photocatalytic degradation and ^·O₂ ⁻ is the main active species. The possible photocatalytic mechanism was further discussed on account of valence band, conduction band positions and possible transition states.