Research On The Modification And Photocatalytic Performance Of Ti₃C₂ MXene-derived TiO₂@C Hybrids

Since the 21st century,people have paid more attention to the energy crisis and environmental pollution caused by the rapid consumption of fossil energy.It is now an urgent task to develop green and sustainable materials for the purpose of the long-term development of human society.Among the most promising semiconductors,titanium dioxide（TiO₂）have been widely studied in the field of photocatalytic hydrogen production due to its nontoxicity,mild reaction conditions,high chemical stability,and no pollution.However,wide applications were limited by its intrinsic drawbacks,such as wide bandgap which only absorbs ultraviolent light occupying 5%in the solar spectrum and easy recombination of photogenerated electrons-holes.Therefore,it is necessary to modify the initial TiO₂ materials.Combining with the carbon-based materials,the conductivity and electron transfer rate were improved.In addition,the specific surface area of carbon-based materials is relatively large,which benefits for the in-situ growth of catalyst,conductive to the exposure of active sites.Furthermore,N doping can effectively broaden the light absorption range of the catalyst and make it respond to visible light.For the novel two-dimensional material,two-dimensional transition metal carbide/carbonitride（MXene）has attracted extensive attention of researchers in many fields.Among them,Ti₃C₂ material has a good application prospect in energy storage materials,catalysts,wastewater treatment,etc.Owing to its good conductivity,hydrophilicity,unique 2D laminated structure and high temperature structural instability,it is expected to use in-situ calcination method to prepare multi-component composite materials with good photocatalytic activity.The main contents are as follows:（1）Taking multilayer Ti₃C₂（m-Ti₃C₂）as titanium source and skeleton,TiO₂@C hybrids were prepared by using one-step high temperature calcination method.The few/monolayer Ti₃C₂（ex-Ti₃C₂）was obtained by exfoliating m-Ti₃C₂ with dimethyl sulfoxide（DMSO）to further improve the photocatalytic activity.The ex-TA@C catalysts were prepared with the same method,and the structure and properties of catalysts were characterized.The anatase TiO₂ nanoparticles with the size of about 50nm are evenly distributed on the surface and edge of the porous carbon matrix.The ex-TA@C hybrids has he increased specific surface area(28.18 m² g^-1)and elevated conduction band,and it delivers a high photocatalytic hydrogen production rate of160.42μmol h^-1 g^-1 and good photocatalytic stability under visible light irradiation.（2）Taking urea as nitrogen source and m-Ti₃C₂ as precursor,N-doped TiO₂@C hybrids（N_x-TA@C）were prepared by freeze-drying and one-step high temperature calcining.When the molar ratio of urea to m-Ti₃C₂ is 1.5%,the photocatalytic activity is the highest.Ultraviolent-visible diffuse reflectance spectroscopy（UV-vis DRS）shows that N_1.5-TA@C catalyst has a good response to UV and visible light,and it delivers a high photocatalytic hydrogen production rate of 109.27μmol h^-1 g^-1 and good photocatalytic stability under visible light irradiation.