Study On Preparation,modification And Photocatalytic Activity Of BiOCl

The environmental pollution caused by the rapid economic and social development cannot be ignored.Photocatalysis is an efficient and environment-friendly technology,which can effectively solve environmental problems.Its core is photocatalyst.BiOCl has attracted people’s attention due to its special structure and performance,but the high recombination rate of photogenerated electrons and holes has hindered the in-depth development of BiOCl.In this paper,citric acid（CA）and g-C₃N₄ were used to modify the surface of BiOCl and construct the heterojunction to improve its photocatalytic performance.The morphology,structure and photocatalytic degradation properties of the photocatalyst were studied by experimental investigation and various test methods,and the possible reaction mechanism was proposed,the results showed that it was workable to improve the photocatalytic activity of BiOCl by surface modification and heterojunction construction.The specific content of the study is as follows:（1）BiOCl/CA materials with different morphologies were obtained by surface modification of BiOCl with CA under hydrothermal conditions.The morphology and structure of BiOCl before and after surface modification were characterized by SEM,XRD,TEM and XPS.The results showed that compared with BiOCl,the particle size of BiOCl/CA modified by surface modification of CA was obviously smaller and the crystal surface of{001}was more exposed.Under ultraviolet light,simulated pollutants including 4-nitrophenol（PNP）,2,4-dinitrophenol（2,4-DNP）,2,4,6-trinitrophenol（2,4,6-TNP）and 2,4,6-trinitrotoluene（TNT）were used to test the photodegradation of BiOCl/CA.The results showed that the effect of different content of CA on BiOCl was different,and BiOCl modified with 10 mmol CA had the most obvious effect on the degradation of PNP,the photodegradation efficiency was 1.45 times of that of pure BiOCl.The electron transfer characteristics and degradation mechanism of the composite were studied by cyclic voltammetry（CV）,electrochemical impedance spectroscopy（EIS）,photoluminescence（PL）and electron paramagnetic resonance（EPR）spectra,the reduction of BiOCl size and the exposure of{001}crystal plane could promote the effective separation of BiOCl electrons from holes,thus improving the photocatalytic activity of BiOCl.（2）The PEI-g-C₃N₄/BiOCl（PEI-CN/BC）heterostructure composites were prepared by electrostatic self-assembly strategy.First,using PEI to modify the surface of g-C₃N₄ to change the surface chargeability of g-C₃N₄ from negative to positive,and then combining it with the negatively charged BiOCl to form a close-contact composites by electrostatic self-assembly.The morphology and structure of the composites were characterized by XRD,SEM,TEM and FT-IR.It was proved that the PEI-CN/BC heterostructure was successfully constructed.The photocatalytic degradation activities of PEI-CN/BC complexes with different contents of PEI-CN under simulated sunlight were investigated by the degradation of the aromatic nitro compounds such as PNP,2,4-DNP and 2,4,6-TNP,when the mass ratio of PEI-CN and BC was 1:2,the obtained 1PEI-CN/2BC could degrade PNP,2,4-DNP and 2,4,6-TNP simulated wastewater completely in 90 min,120 min and 120 min,respectively.The photocatalytic degradation mechanism of the system was studied by means of CV,EIS,Mott-Schottky curve（MS）,PL and EPR.The results showed that the successful construction of the PEI-CN/BC heterostructure improved the electron-hole separation efficiency of BiOCl,which was the internal reason for the improvement of its photocatalytic performance.