Effect Of Ice Water Quenching On TiO₂-based Materials Structure And Photocatalytic Properties

TiO₂ is an excellent photocatalytic material.Compared with other catalytic materials,TiO₂ possesses good photocatalytic activity,and has significant advantages in safety,chemical stability and cost,thus has enormous potential in energy conversion,environmental governance etc.But TiO₂ has a wide band gap?rutile phase 3.0 eV,anatase phase 3.2 eV?,that only UV light can excite TiO₂ to produce photo-generated carriers,then the photocatalytic reaction can proceed smoothly.Researchers has made lots of efforts to enhance the photocatalytic activity of titanium dioxide,and current research focuses on doping and loading to modify TiO₂.Studies have shown that the impurities can be introduced in TiO₂ by doping method,which could reduce the band gap width,excite TiO₂ under visible light and improve material utilization efficiency of visible light.However,dopant ions will be photogenerated carrier recombination centers,which is harmful to improving the photocatalytic activity of TiO₂.Ti³⁺ions self-dopant in TiO₂ is also a focus of research in recent years.Ti³⁺ions in the TiO₂ can form defect levels inside band gap,thus expanding the range of visible light response range.TiO₂ is a typical non-stoichiometric material,oxygen in TiO₂ lattice can escape at high temperatures easily,resulting in the formation of Ti³⁺ions and oxygen vacancy defects.Therefore in this paper we propose ice water quenching method of treating TiO₂,keep the high temperature phase structure of TiO₂,then the crystal structure and photocatalytic properties of titanium dioxide are investigated through analysis techniques such as XRD,Raman,TEM,XPS and EPR etc.On this basis,Cu₂O and Au is loaded on TiO₂ by precipitation deposition method,and photocatalytic activity of samples under visible light irradiation is studied.Conclusions have been made as follows:?1?P25 samples and TiO₂ samples prepared by hydrolysis method?Hy-TiO₂?quenched at high temperature have lower orderliness.Quenched samples?que-TiO₂?at 1200oC exhibit poly-crystallization trend,with internal lattice fringe disorder and crystal defects increasing.Ti³⁺ions occur in quenched samples,and as the quenching temperature increases,Ti³⁺ions concentration will increase.?2?Quenched samples have better visible light absorption capacity.Quenched samples have a higher photocatalytic activity than samples cooled in the furnace?non-TiO₂?.Under UV irradiation the photocatalytic reaction rate constant of Hy-TiO₂900oC que-TiO₂ can reach 2.6 times of non-TiO₂,while P25 1000oC que-TiO₂sample can reach 2.2 times of non-TiO₂.But under visible light irradiation que-TiO₂samples present lower photocatalytic activity than non-TiO₂.?3?The Visible light absorption of TiO₂ loaded with Cu₂O and Au is improved.It's confirmed that Cu loaded as Cu⁺,while Au loaded as Au⁰.The quenched samples loaded Au and Cu₂O present higher photocatalytic activity under visible light irradiation.The Ti³⁺ions inside the quenched samples play an important role in the visible light catalytic reactions.