Preparation And Characterization Of B,F,P-TiO₂/Fe₃O₄ Nano-photocatalyst With High Carrier Separation Efficiency

Aiming at the problem of low efficiency and difficult recovery of nano-TiO₂,based on the synergetic of Ti O₂ surface modificatin and magnetic Fe₃O₄-coupling,a high-performance B,F,P-TiO₂/Fe₃O₄ photocatalyst with magnetic recovery function was developed,which providing a new method for the application of photocatalytic technology in wastewater treatment and providing a new strategy for further development of new materials with high photocatalytic performance.First,B,F,P-Ti O₂ nano-photocatalyst with high photocatalytic activity under simulated solar irradiation was successfully prepared via the microwave-hydrothermal method,using TiCl₄ as titanium source,H₃BO₃ as boron source,NH₄F as fluorine source and H₃PO₄ as phosphorous source.Through orthogonal design experiments showed that the process of B,F and P co-doped TiO₂ nanaphotocatalyst,among B doping with 1wt%,F doping with 2.5wt%and P doping with 1wt%.The B,F,P-TO nano-photocatalyst was characterized by XRD,TEM,BET,XPS,FT-IR,DRS,SPS,PL and FL.It was investigated of B,F and P surface modification on the surface structure and properties of TiO₂.BET showned that the P surface modification playded an important role in improving the TiO₂ surface surface texture of TiO₂,which was beneficial to increasing the active site of the reactants and shorten the diffusion length of the carriers.On the contrary,B and F doping leads to decreasing in the specific surface area of TiO₂.Thus,B,F,P-TO has a greater specific surface area than TiO₂,mainly due to the fact that the phosphate group has been doping to the lattice interface.PL spectra has showed that B,F or P doping can prevent the recombination of photogenerated carriers,which B,F and P tridoping surface modificatin further enhance the inhibition.It was confirmed that B,F,P tridoping surface modificatin of Ti O₂ had synergistic effect on the inhibitin of carrier recombination.Among them,the F surface modification of TiO₂ produced the highest SPS signal intensity,and F-doping played an important role in electron-hole separation,which due to F had strong electronegativity.B,F and P tridoping can further increase the surface modification of the SPS response,indicating that tridoping has produced synergistic effect.Based on the synergetic effect of B,F,and P tridoping and Fe₃O₄ coupling,a magnetically recoverable B,F,P-Ti O₂/Fe₃O₄ nanocomposite photocatalyst was prepared via the microwave-hydrothermal process and subsequent calcination after grinding B,F,P-Ti O₂ and Fe₃O₄ nanosheets in an agate mortar.The synergetic effect of B,F,and P tridoping and Fe₃O₄ coupling on promoting the photogenerated charge separation was confirmed by photoluminescence spectroscopy（PL）,surface photovoltage spectra（SPS）,and electrochemical impedance spectroscopy（EIS）.B,F,P-TiO₂/Fe₃O₄ exhibited the typical superparamagnetic behavior and the sufficient magnetic recycling property.The photogenerated charge separation efficiency,which was superior to other factors including the photoabsorption ability,phase structure,surface hydroxyl,and textural property,played a dominant role in improving the photoactivity.B,F,or P single-doping promotes the separation of photogenerated charge carriers,which should be due to the manipulation of internal electric fields within TiO₂ crystal lattices through polar surface terminations,because doped B,F,or P has a higher electronegative than Ti.Moreover,B,F,and P tri-doping can further facilitate the photogenerated charge separation,which should be ascribed to a synergetic effect of different micro-nano region on the crystal lattice surface.·OH radical was confirmed to be a main activated species in the photocatalytic processes.No positive correlation between surface hydroxyl content and·OH radical generation amount was observed.As well as the excellent photoactivity for the degradation of 4-chlorophenol（4-CP）under simulated sunlight irradiation(K_app=1.1×10^-2 min^-1),equal to that of commercial P25 Ti O₂.Therefore,B,F,P-TiO₂/Fe₃O₄has excellent photocatalytic activity due to the three element doping and Fe₃O₄ coupling to promote the photoinduced charge separation.