Synthesis And Characterization Of Titanium Carbide-based Composites And Their Application On The Degradation Of Rhodamine B

In the past decade,two-dimensional layered materials such as graphene,hexanal boron nitride?h-BN?,transition metal dichalcogenides?TMDs?,transition metal oxides?TMOs?,layered double hydroxides?LDHs?has attracted widespread attention,since they exhibit excellent performances in many fields,such as electrochemical energy storage,gas sensing and field effect transistors.Two-dimensional transition metal carbide?MXene?is an emerging graphene-like layered material with high specific surface area,high electrical conductivity and hydrophilicity,as well as flexibility and chemical stability.At present,MXene has become a hot-spot in the scientific research field owing to its potential applications in the fields of sewage treatment,energy storage,catalysis,sensing and biomedicine.Since traditional semiconductor metal oxide photocatalysts?e.g.TiO₂?mainly absorb high energy UV light due to their wide band-gaps,the catalytic efficiency and the utilization of sunlight are usually very poor when they are used as the photocatalysts.To overcome the above disadvantages,a series of MXene-based composite photocatalysts was designed and synthesized in this dissertation through a mild liquid phase route,employing titanium carbide as raw material.The absorption range was successfully extended to the visible region and simultaneously,the recombination of photogenerated electrons and holes was effectively inhibited.As a result,the photocatalytic efficiency was obviously improved.Furthermore,the mechanisms of the photocatalytic degradation were investigated.The main contents are summarized as follows:1.Synthesis and photocatalytic properties of MXene-based composite catalyst MXene/TiO_2-x.MXene Ti₃C₂ with sheet-like nanostructures was first prepared through a simple etching route at room temperature for 48 h,employing bulk Ti₃AlC₂ as the precursor and hydrofluoric acid as the etching agent.Subsequently,the obtained Ti₃C₂nanosheets were treated with an appropriate amount of hydrogen peroxide?H₂O₂?at room temperature for 15 min to successfully prepare a porous MXene/TiO_2-x-x composite containing 2 nm TiO_2-x-x nanodots.Photocatalytic degradation experiments showed that the as-obtained MXene/TiO_2-x-x composite owned excellent photocatalytic activity for the degradation of RhB.Under irradiation of the simulated sunlight,the degradation efficiency of RhB reached 96.10%in 10 min in the presence of the catalyst with a low-concentration of[Ti]=150 ppm.It was found that the as-obtained MXene/TiO_2-x-x catalyst also exhibited good cycle stability.After 10 cycles,the catalytic degradation efficiency hardly reduced.Further investigation uncovered that the improved photocatalytic performance of the present catalyst should be attributed to the synergistic effect of the photocatalysis and the Fenton-like oxidation,in which the formation of Ti³⁺ions played an important role.2.Solvothermal synthesis and photocatalytic properties of MXene-based composite catalyst TiO₂/MXene.TiO₂/MXene nanocomposites were successfully prepared by a solvothermal method using Ti₃C₂ and tetrabutyl titanate?TBOT?as raw materials in the presence of acetic acid with appropriate amounts.Photocatalytic degradation experiments exhibited that the as-prepared TiO₂/MXene nanocomposites presented excellent catalytic ability to the photodegradation of RhB under irradiation of the simulated sunlight.In the presence of 10 mg catalyst,the degradation efficiency of RhB reached 42.24%and assistance with 200?L H₂O₂,the degradation efficiency of RhB got 95.32%after irradiating for 60 min,which is 2.0 times as big as the photocatalytic degradation efficiency.It was found that the as-obtained TiO₂/MXene catalyst also exhibited good cycle stability.After 5 cycles,the catalytic degradation efficiency lost 10.70%.Further investigation uncovered that the improved photocatalytic performance of the as-obtained TiO₂/MXene nanocomposite catalyst should be derived from the synergistic effect of the photocatalysis and the Fenton-like oxidation,in which the production of reactive oxygen species?ROS?acted as a crucial role.3.Hydrothermal synthesis and photocatalytic properties of MXene-based composite catalyst Fe₃O₄/MXene.Fe₃O₄/MXene composites were successfully prepared by a one-step hydrothermal route at 180?C for 12 h,using Ti₃C₂ and FeCl₂·4H₂O as raw materials.Experiment showed that the as-synthesized Fe₃O₄/MXene nanocomposites possessed excellent photocatalytic activity for the degradation of RhB under irradiation of the simulated sunlight.In the presence of 10 mg catalyst,the degradation efficiency and reaction rate constant of RhB reached 50.94%and 0.0070 min^-11 respectively and assistance with 200?L H₂O₂,the degradation efficiency and reaction rate constant of RhB got 96.07%and 0.0443 min^-11 respectively after irradiating for 60 min.It was found that the as-obtained Fe₃O₄/MXene catalyst also exhibited good cycle stability.After 5 cycles,the catalytic degradation efficiency reached 86.54%which was lost 9.92%.Further investigations found that Ti₃C₂ and Fe₃O₄ could be used as photocatalyst and Fenton-like reagents at the same time.Thus,the synergistic effect of the photocatalysis and the Fenton-like oxidation caused the improved catalytic performance of the as-obtained Fe₃O₄/MXene composite catalyst.