Preparation Of N-Ti₃C₂ MXene Based Composites And Their Photocatalytic Properties

MXene was first synthesized in 2011,and it has attracted attention due to its unique two-dimensional layered structure,excellent electrical conductivity,and abundant functional groups on the surface,and has been widely used in photocatalytic energy conversion and environmental water pollution treatment.In this paper,we obtained more efficient composite catalysts based on Ti₃C₂ modification for the performance of photocatalytic degradation of organic pollutants and explored its photocatalytic degradation mechanism.The details are as follows:（1）Two-dimensional layered nanomaterials Ti₃C₂ were prepared by HF acid etching,intercalated with dimethyl sulfoxide（DMSO）,and doped with urea as the nitrogen source to obtain nitrogen-doped Ti₃C₂（N-Ti₃C₂）.The mass fractions according to the nitrogen doping were N-Ti₃C₂ 1:2 MXene,N-Ti₃C₂ 1:5 MXene,N-Ti₃C₂ 1:8 MXene,and N-Ti₃C₂ 1:10MXene.The results showed that the photocatalytic performance of N-Ti₃C₂ was significantly enhanced,and among them,N-Ti₃C₂ with the nitrogen doping ratio of 1:8 showed the best photocatalytic activity.After 40 min of UV light irradiation,the N-Ti₃C₂ 1:8 MXene material degraded methyl orange（MO）up to 99.93%,and its catalytic rate was about ten times that of Ti₃C₂ MXene,and the N-Ti₃C₂ photocatalyst still showed good stability after four cycles.In addition,the active substances that play a major role in the photocatalytic process are·OH,e^-,and·O₂^-,which were also explored by radical capture experiments.（2）The g-C₃N₄ was prepared by calcination of urea at a high temperature of 550℃,and then the N-Ti₃C₂ formed after doping modification was ultrasonically compounded with g-C₃N₄ to synthesize N-Ti₃C₂/g-C₃N₄ composites,and the photocatalytic performance was tested.The results showed that the best photocatalytic effect was exhibited when the mass ratio of N-Ti₃C₂/g-C₃N₄ was 1:5.The removal rate of MO reached 97.6%after 120 min of visible light illumination,and its kinetic reaction rate was 8.6 times higher than that of g-C₃N₄alone,which may be due to the formation of heterojunctions between g-C₃N₄ and N-Ti₃C₂,thus further separating the photogenerated electrons and holes and improving its photocatalytic performance.The prepared N-Ti₃C₂/g-C₃N₄ composite photocatalyst still has good photocatalytic performance after four cycles.In addition,the active substances that play a major role in the photocatalytic process are·O₂^-and·OH,which were also explored by radical trapping experiments.（3）BiOCl was formed by solvent heat reaction of bismuth nitrate pentahydrate and potassium chloride mixed with ethylene glycol and compounded with different ratios of N-Ti₃C₂ to form N-Ti₃C₂/BiOCl composite semiconductor material.The performance was also tested,and the results showed that the best photocatalytic effect was exhibited when the mass ratio of N-Ti₃C₂/BiOCl was 15%.The visible light irradiation degraded 98.86%of rhodamine B（RhB）after 20 min,and its catalytic rate was much larger than that of BiOCl.The good photocatalytic performance of the N-Ti₃C₂/BiOCl nanocomposite was mainly due to its uniform mesoporous coating,high electrical conductivity,and narrow forbidden bandwidth.And it was found that the active substances that play a major role in the photocatalytic degradation process are h⁺and·O₂^-by the experimental study of radical capture.