In situ construction of ridge-like PVDF/TiO2/CQDs hybrid film with multiple electron transfer channels based on S-scheme heterostructure and dynamic "piezo-photocatalytic" mechanism for dye removal

The ridge-like PVDF/CQDs-TiO2@CQDs hybrid piezo-photocatalytic film was fabricated via an "in situ hydrothermal-vapor induction" method, in which the S-scheme TiO2@CQDs heterostructures were grown in situ and uniformly immobilization onto the polyvinylidene fluoride (PVDF) film surface through Ti-F coordination bonds. The effects of hybrid film morphology, carbon quantum dots (CQDs) doping, and flow rate on piezo-photocatalytic degradation performance were investigated. The ridge-like microstructure increased the exposure of adsorption and catalytic active sites. The film reactor driven by the flow of dye solution and light illumination promoted the adsorption of pollutants while establishing a dual built-in electric field (IEF) between the piezoelectric PVDF and catalysts, TiO2 and CQDs, which accelerated photogenerated charge transfer and separation. Finally, a dynamic piezo-photocatalytic process was realized for the efficient and synergistic degradation of RhB. The reaction rate constant (ks) of the dynamic piezo-photocatalytic degradation was about 2.3 times that of the static photocatalytic process. Structural optimization and density functional theory (DFT) calculations of Rhodamine B (RhB) molecules were performed using Gaussian software. The degradation products, degradation pathways, and degradation mechanisms of RhB were thoroughly studied by combining the results of total organic carbon (TOC), DFT and liquid chromatography mass spectrometry (LC-MS).