Preparation And Properties Research Of Nano Si And Nano Ag/TiO₂ Composite Photocatalyst

A large number of organic pollutants in modern industrial production and daily life are breaking the earth's environment.Titanium dioxide?TiO₂?,as a high-efficiency semiconductor photocatalytic clean material,can not be applied in large quantities because of the narrow light response range.As a narrow bandgap semiconductor material,silicon?Si?can produce higher concentrations of photogenerated carriers.In this paper,Si nanoparticles from solar cell cutting waste and nanosilver particles?AgNPs?are composited with TiO₂ in different sizes and morphologies prepared by different processes to form a ternary composite photocatalyst.The results of the study are as follows:?1?Si particles were composited with P25 TiO₂ and TiO₂ prepared by sol-gel method using the hydrothermal method.The effect of the mixing ratio of Si nanoparticles on the visible light absorption ability and photocatalytic capacity of TiO₂was studied.When the ratio of Si was 1%wt,the light absorption edges of Si/TiO₂?25?and Si/TiO₂?sg?were red-shifted to 440nm and 430nm,respectively.After 2.5h of catalytic reaction,the degradation rate of RhB by 1%Si/TiO₂?25?was 7 percentage points higher than that of TiO₂?25?,and the degradation rate of MB after 3.5h catalytic reaction was 9.4 percentage points higher than that of TiO₂.After 3.5h illumination,the degradation rate of 1%Si/TiO₂?sg?to RhB and MB increased by 6.2 percentage points and 6.7 percentage points respectively compared to TiO₂?sg?.The results indicated that the band gap width of Si was so narrow that it was easier to absorb light and generate a large number of e^-and h⁺.Due to the higher conduction band level of Si,the photogenerated e-could easily transfer spontaneously to the TiO₂,which improved the photocatalytic efficiency.?2?The AgNPs were fabricated on the surface of the Si particles by the in-situ reduction method of the aqueous phase to form silver-coated silicon particles?Ag@Si?with good contact.Ag@Si/TiO₂ ternary composite based on different TiO₂ was formed by using hydrothermal method.The high degradation effects of RhB and MB indicating that AgNPs has good photogenerated charge separation ability and special surface plasmon resonance effect,which enhances the photocatalytic activity of the composites.?3?The needle-like TiO₂ inclusion layer was prepared on the surface of functionalized Si NPs by hydrothermal method with temperature control to form a sea urchin-like Si/TiO₂ composite photocatalyst?UTS?.The heterojunction formed by Si/TiO₂ broadened the absorption range of light,so that the utilization rate of visible light is improved.After the UTS modified by AgNPs,the surface adsorption capacity and electron separation were further improved,and the recombination of e^-and h⁺was greatly weakened.After 3.5h the degradation rates of Ag@UTS to RhB and MB were increased to 96.3%and 82.8%,respectively.It was realized that catalytic activity has been significantly improved,and the composite process has good generalization property.