Controllable Preparation Of TiO₂@Ti₃C₂T_x（MXene） Photocatalyst And Its Catalytic Performance And Mechanism

Photocatalysis is considered to be not only a green chemical process to eliminate pollutants and obtain sustainable energy,but also an effective solution to solve the energy crisis and environmental pollution issues.Titanium dioxide（TiO₂）is one of the most traditional and commonly used photocatalysts.However,it’s main limiting factors are the narrow light absorption region and carrier combination.Therefore,regulating the structure of TiO₂-based catalysts,improving their charge separation efficiency and optical quantum efficiency are of great significances for promoting the development of photocatalysis technology.As the representative of MXene materials,Ti₃C₂T_x（T=-F,-OH,-O）has a unique two-dimensional structure,excellent conductivity and electronic transmission efficiency,which has attracted much attention in recent years.In view of the shortcomings of carrier recombination of TiO₂and the advantages of high carrier mobility of Ti₃C₂T_x,a series of TiO₂@Ti₃C₂T_xphotocatalysts have been designed and controllable standby.The performance of the photocatalysts were evaluated comprehensively and their catalytic mechanism was investigated.The main research results of this thesis are as follows:（1）TiO₂was grew in-situ on Ti₃C₂T_xthrough a hydrothermal and post-heat treatment process.The surface terminated group of Ti₃C₂T_xin the composite was partially removed and unified into-O adsorption,and the urchin-like TiO₂/Ti₃C₂O_xcomposite with high specific surface area was formed.Meanwhile,the content of TiO₂in the material could be adjusted by the volume of H₂O₂.The optimum photocatalytic hydrogen production（HER）performance was 346.8μmol g^-1h^-1,which was higher than that of pure anatase（A-TiO₂）,with an apparent quantum yield（AQE）of 7.67%at 313 nm.In addition,the catalyst could also effectively degraded levofloxacin（LEV）.The study of catalytic mechanism shown that Ti₃C₂O_xwith a large amount of-O groups adsorbed on the surface had a high work function（Φ）,which could act as an e^-trapping agent in the photocatalytic reaction.（2）Pt nanoparticles were loaded on TiO₂/Ti₃C₂O_xby photo-induced in-situ deposition.Benefit from the Ti₃C₂O_xwith highΦcould transfer e^-,enable reduce the e^-aggregation on the TiO₂.Compared with Pt-TiO₂without Ti₃C₂O_x(Pt_0.2T（P）),and Pt-TiO₂/Ti₃C₂O_xprepared by chemical reduction method(Pt_0.2TM（I）),photo-induced fabricated Pt-TiO₂/Ti₃C₂O_x(Pt_0.2TM（P）)exhibited higher photocatalytic H₂production.In addition,photodeposited Au and Ag on TiO₂/Ti₃C₂O_xcould also show this carrier effect.The photocatalytic mechanism shown that Pt supported catalysts with high reduction state and small size could be obtained under the synergistic action of light induction and e^-trapping agent of Ti₃C₂O_x,which has better photocatalytic performance.（3）Choline chloride（ChCl）and oxalic acid（OA）were used as the hydrogen bond acceptor and donor,respectively,for the deep eutectic solvent（DES）.The adjustment of the crystalline phase ratio of anatase/rutile in TiO₂was achieved by changing the molar ratio of the hydrogen bond acceptor to the donor.When the molar ratio of ChCl to OA was 4:5,the prepared TiO₂（TiO₂-C/O（4:5））achieved the best photocatalytic activity of 246.59μmol g^-1h^-1.Moreover,the catalyst could also exhibit a rapid degradation of ciprofloxacin（CIP）.（4）Few layers of Ti₃C₂T_x,Ti₃C₂T_xquantum dots and Pt were used as co-catalysts to enhance the photocatalytic activity of heterogeneous TiO₂prepared by DES.The HER performance of 0.2wt%Pt loaded on TiO₂-C/O（4:5）were 9.63 and 6.04 mmol g^-1h^-1,respectively.The optimal HER performance of TiO₂-C/O（4:5）loaded with few layers of Ti₃C₂T_xand Ti₃C₂T_xquantum dots were 440.55 and 890.49μmol g^-1h^-1,respectively.The HER performance of depositing 0.2wt%Pt on the basis of few layers of Ti₃C₂T_xsupported TiO₂-C/O（4:5）reached 28.92 mmol g^-1h^-1,which was much higher than that of TiO₂-C/O（4:5）.