Construction Of 2D/2D Photocatalytic Composites Based On G-C₃N₄ With Enhanced Visible-light-driven Photo-catalytic Performance

Photocatalytic technology is an effective method to solve the energy crisis and environmental pollution.However,there are still many shortcomings on photocatalytic technology such as low visible light utilization and high prices of noble metal photocatalytic material.So,efficient and low-cost visible photocatalytic nanomaterials has become a hot research direction.The g-C3N4 bulks is made up of two-dimensional?2D?layer which similar to graphene,and it will change into layers after stripped.However,the pure g-C₃N₄ nanosheets still hold on defects such as low utilization of visible light and fast recombination of photogenerated charges.Constructing heterojunction nanocomposite based on g-C₃N₄ nanosheets can make full use of 2D structure of g-C3N4,it would enhanced visible light absorption rate,improve the photogenerated charges separation efficiency and accelerate the surface catalytic reaction of nanocomposite,which in turn improve the photocatalytic activity.Hence,we build different types of 2D/2D heterojunction based on g-C3N4 nanosheets,and explored the enhancement of the photodegradation of organic pollutants as well as the photoreduction of CO₂ with visible light,mainly achieved following results:1.The ultrathin g-C₃N₄ nanosheets was prepared by thermal stripping,and the g-C₃N₄ static position was converted to positive by the process of protonation.At the same time,rGO/g-C₃N₄ nanocomposite was obtained by the electrostatic self-assembly effect.Compared with g-C₃N₄ nanosheets,the photodegradation of MO and photoreduction of CO2 with 3%rGO/g-C3N4 increased 2.19 and 2.32 times respectively.SEM,TEM,DRS,FTIR and PL indicate that the prepared rGO/g-C₃N₄ nanocomposite possesses strong visible light absorption capacity,and there might be a strong interaction between rGO and g-C₃N₄ nanosheets.In rGO/g-C₃N₄ nanocomposite,rGO is mainly used as an electronic storage unit,and the photogenerated electrons will be stored in rGO which would delay the compound of electron-hole pairs,thereby improving the photocatalytic performance.2.The solvent thermal method was used to generate MoS₂ in the ultrathin g-C₃N₄nanosheets,and the 2D/2D MoS₂/g-C₃N₄ nanocomposite was obtained by ultrasonic stripping.Compared with g-C₃N₄ nanosheets,the total production of CO and CH₄ of photocatalytic reduction CO₂ using 3%rGO/g-C₃N₄ increased 3.05 and 2.99 times respectively.Photocatalytic mechanism shows that the direct Z scheme may be formed between g-C₃N₄ nanosheets.The results show that the building of 2D/2D direct Z type can not only accelerate the photogenerated charges separation efficiency,but also improve the oxidation and reduction ability of electrons and holes,which can further improve the photocatalytic activity of g-C₃N₄ nanosheets.3.Solvent thermal method was used to generate MoS₂ on the graphene sheets,ultrasonic stripping way was used to get 2D/2D MoS₂/GO heterojunction,and than we composited MoS₂/GO with the protonation g-C₃N₄ nanosheets through the effect of electrostatic self-assembly.At the same time,we used hydrothermal method to reduce GO in cause of getting a sandwich structure of 2D MoS₂/r GO/g-C₃N₄ nano heterojunction.Compared with g-C₃N₄ nanosheets,the total production of CO and CH₄of photocatalytic reduction CO₂ using 2%MoS₂/rGO/g-C₃N₄ increased 7.75 and 2.89times respectively.The photocatalytic mechanism shows that the constructed indirect Z structure by the introduction of the electronic medium rGO can further improve the separation efficiency and delay the recombination of the electron hole.The above results show that 2D/2D nanocomposite have the advantage of large surface area,rich binding site and extremely short electron transport distance.The construction of 2D/2D nanocomposite can improve the contact area with the reactants and change the electron orientation to delay the recombination of the electron hole.In addition,the Z scheme can improve the oxidation ability of the electron hole,and further play the advantage of the short distance of electron transport on the 2D/2D structure,thus improving the photocatalytic performance.