Multi-Field Synergistic Enhancement Of Photogenerated Carrier Transport Efficiency Of Defect BiOCl-Based Heterojunctions

Photocatalysis is considered as an effective way to solve the current water pollution problem.It is well known that significant photogenerated carrier recombination and poor light absorption are major bottlenecks for photocatalytic applications.However,traditional oxide photocatalysts have poor absorption capacity for visible light due to their wide band gaps.Therefore,its practical application is limited.Among them,carbon quantum dots（CQDs）are promising new carbon nanomaterials photocatalysts with excellent electron transfer efficiency and easily modulated light absorption range.Meanwhile,due to its unique electronic structure and band gap,the doped C/Brof graphitized carbon nitride（g-C₃N₄）greatly broadens the range of light response and enhances the separation efficiency of photo-induced carriers.In addition,bismuth oxychloride（Bi OCl）has attracted much attention due to its high visible light catalytic activity.Due to lattice mismatch,the two photocatalysts induce lattice distortion at the interface to generate interfacial oxygen vacancies（IOVs）.Appropriate IOVs can reduce the transport resistance of photoinduced carriers at the interface,promote the separation of photogenerated carrier and improve the photocatalytic performance.The photocatalytic degradation mechanism of tetracycline pollutants was systematically studied by interfacial electric field,thermoelectric field induced by Seebeck effect and the hypothesis of"surface/interface lewis acid-base pair".Therefore,in this paper,CQDs,CCN,BrCN and Bi OCl were used to synthesize a series of composite materials of CQDs/Bi OCl,CCN/Bi OCl and BrCN/Bi OCl,respectively.The research contents of this paper are as follows:（1）A novel CQDs/Bi OCl Schottky heterojunction with moderate OVs was successfully prepared through using maltitol as a carbon source,and its photocatalytic performance was investigated with TC-HCl as the target pollutant.Among them,OVs concentration was regulated by introducing CQDs.The separation efficiency of photogenerated carriers,the photocatalytic performance of the as-prepared samples,and the contribution of free radicals to the photocatalytic activity in the reaction process were investigated through multiple characterizations.（2）CCN was obtained by doping g-C₃N₄using Coca-Cola as the C source.Combined with microwave-assisted method,CCN/Bi OCl heterojunction composites were successfully prepared.The concentration of IOVs and the light response range were regulated by the content of CCN,and the contribution of each active species was calculated by using the free radical contribution model.Thus,the double electric field can drive the generation of·O₂^-in the CCN/Bi OCl heterojunction and promote the degradation of TC-HCl.Furthermore,the photocatalytic degradation mechanism of TC-HCl by CCN/Bi OCl heterojunctions under the synergistic effect of interfacial electric field,defect engineering,and thermoelectric electric field induced by the Seebeck effect is discussed.（3）Using cetyltrimethylammonium bromide（CTAB）as Brsource,Br-doped g-C₃N₄（BrCN）was successfully prepared by calcination method.The BrCN/Bi OCl heterojunction was successfully constructed by microwave-assisted technique.Multiple characterization and activity experiments revealed that BrCN/Bi OCl had excellent photocatalytic degradation performance for OTC-HCl.At the same time,the effects of appropriate IOVs concentration and free radical/non-radical contribution ratio on catalytic performance were studied.Driven by interfacial electric field and thermoelectric field,electrons are separated effectively through efficient electron transport channel.In addition,the synergistic"surface/interface lewis acid-base pair"hypothesis can increase the transfer efficiency of photogenerated carriers and improve the photocatalytic performance.