Study On Effective Transfer Regulation And Mechanism Of Two-dimensional Photocatalytic Material Photogenerated Carriers

Environmental governance and the development of efficient and sustainable renewable energy are the two major problems in current social development.Photocatalytic technology can achieve efficient photocatalytic degradation of pollutants,photocatalytic sterilization,water splitting and CO₂ reduction,etc.In addition,photocatalysts have the advantages of non-toxic,cheap,stable and reusable,therefore photocatalytic technology has become a research hot spot in the field of energy and environment.Two-dimensional photocatalytic materials have unique electronic and structural advantages and are ideal materials for achieving highly efficient photocatalytic reactions.However,the high recombination rate of photogenerated carriers in two-dimensional photocatalytic materials greatly limits the improvement of photocatalytic performance.The separation efficiency of photogenerated carriers can be improved by adjusting the interface charge and band structure.This paper focused on the problem of the low transfer efficiency of photogenerated carriers.Defect regulation,heterojunction recombination,and surface modification were used to achieve efficient spatial separation and transfer regulation of photogenerated carriers,so as to improve the photocatalytic efficiency of photocatalysts.Through extensive structure characterization and photocatalytic performance research,the effective transfer regulation mechanism for improving photogenerated carriers in two-dimensional photocatalytic materials was explored,which provided new insights and ideas for the design and construction of charge transfer control in two-dimensional photocatalytic materials.The following aspects were studied in this paper:1.Aiming at the problem that the traditional method of preparing carbonized Titanium dioxide（TiO₂）needed an external carbon source,we used in-situ doping to synthesize nano carbon modified C-TiO₂ containing certain oxygen vacancies.Then,graphitic carbon nitride（g-C₃N₄）was deposited in-situ on the surface of the defective C-TiO₂ to prepare g-C₃N₄@C-TiO₂ composite photocatalyst with direct Z-scheme mechanism,so as to promote the effective transfer and separation of photogenerated carriers and realize the efficient photocatalytic degradation of rhodamine B（Rh B）and phenol.The results had shown that the two-dimensional g-C₃N₄ was tightly bounded on the surface of the defective C-TiO₂ byπ-πconjugation and bonding interaction.Appropriate concentration of C doping and the surface modification of g-C₃N₄effectively introduced new nonlocal impurity levels and high surface active sites into the photocatalytic system.Thus,the effective separation and transfer of photogenerated carriers were achieved,and the photocatalytic activity of the g-C₃N₄@C-TiO₂ composite photocatalyst was significantly enhanced.2.S-scheme and 2D/2D morphological BP/BiOBr nanoheterojunction photocatalytic composites with strong chemical bonding,large contact interfaces,and unique band structures were constructed by a simple liquid-phase ultrasound combined with solvothermal method,which realized the effective transfer control of photogenerated carriers.BP/BiOBr had shown highly efficient photocatalytic performance for the photocatalytic degradation of tetracycline（TC）,production of O₂and H₂O₂.Studies had shown that appropriate solvothermal treatment was very beneficial to the close combination of two-dimensional BP nanosheets and BiOBr.The construction of S-scheme two-dimensional nanoheterojunctions with reasonable matching band structure,strong interface interaction,high oxidation-reduction and excellent space charge separation ability can effectively improve the visible light driven photocatalytic performance and the separation efficiency of photogenerated carriers of BP/BiOBr composite photocatalyst.3.For the first time,CN/rGO@BPQDs composite materials with tight interface binding and high-efficiency photocatalytic activity were constructed by using the porous g-C₃N₄（CN）self-trapping pore confinement effect andπ-πinteraction between CN and rGO.Zero dimension rGO@BPQDs was firmly anchored on mesoporous CN by self-trapping pore confinement effect andπ-πinteraction to form n-n type high-low junction CN/rGO@BPQDs composite with high photocatalytic activity effectively improved the chemical stability of BPQDs,expanded the spectral response range of photocatalyst and improved the separation efficiency of photocarriers.The influence of photocatalysis system on photon absorption efficiency was evaluated by extinction coefficient and optical thickness.The results had shown that CN/rGO@BPQDs had excellent photocatalytic activity for Rh B,TC degradation and H₂O₂ production under visible light irradiation.Reasonable surface modification was conducive to improving the chemical stability of BPQDs,and the n-n type junction formed by the interal electric field was useful to improve the charge space separation ability and photocatalytic efficiency of the CN/rGO@BPQDs composite photocatalyst driven by visible light.