Study On The Band Regulation And Photoelectrochemical Performances Of BiOCl

The band gap of semiconductors is the main factor affecting the photoelectrochemical and photocatalytic properties of semiconductor photocatalyst.The semiconductor light absorption range is too narrow if the band gap is too large.The photogenerated electrons and holes can be easily recombined and photo-generated electrons and holes have weak redox ability if the band gap is too narrow.Therefore,it is of great significance to regulate the energy band of semiconductors according to the actual application.BiOCl have good photocatalytic activity and photocatalytic stability due to the unique layered structure of BiOCl,good optical properties and the built-in electric field formed by[Bi2O2]2+ and Cl elements.Therefore,in this paper,BiOCl is regulated by different semiconductor band regulation methods to achieve its application under different requirements.A series of microspherical BiOCl photocatalysts with graded structure modified by oxygen vacancy were prepared by a simple one step hydrothermal method.The oxygen vacancies in the prepared BiOCl samples were confirmed by Raman,XPS and ESR.The photoelectrochemistry and photocatalytic degradation of norfloxacin showed that the BiOCl-140 samples with abundant oxygen vacancies had larger photocurrent density and better photocatalytic degradation of norfloxacin compared with the BiOCl-140-400 samples without oxygen vacancies under the visible light irradiation.What's more,norfloxacin could be complete mineralized by BiOCl-140-400 with a long time visible light irradiation,and it had better photocatalytic stability.There are two main reasons for the improving of photochemical and photocatalytic properties of BiOCl-140 under visible light irradiation,the one is that the special hierarchical structure of the BiOCl-140 sample prepared by the hydrothermal method,which can absorb the visible light repeatedly to enhance the photon capture ability.The other is that oxygen vacancies form a doping level in the BiOCl band gap,and at the same time,the valence band shifts negatively,thus shortening the energy band to 1.77 eV and extending the optical absorption range to 700 nm.The synergetic effect of oxygen vacancies and microstructure results in an increase in the visible absorption range and absorbency of BiOCl.A series of BiInOCl photocatalysts with different Bi:In ratios were prepared by a simple one step hydrothermal method.It was found that the microsphere structure was still presented in the solution of In to BiOCl,and the specific surface area was greatly increased.The results of photoelectrochemistry and photocatalytic properties showed that the BiInOCl-1:2 sample has the best photochemical properties and the photocatalytic degradation of norfloxacin.It was found that there are two main reasons for the improvement of photoelectrochemical and photocatalytic performance of BiInOCl-1:2.Firstly,the larger specific surface area enhances the adsorption capacity of BiInOCl-1:2 samples,and the number of active sites increases.Secendly,the addition of In positively shifts the valence band of BiInOCl,and at the same time it negatively shift the conduction band of BiInOCl,so that both the oxidation capacity and the reduction ability are simultaneously enhanced.At the same time,the free radical detection shows that there are many hydroxyl radicals and superoxide radicals in the solution,which enhanced redox ability of BiInOCl,thus enhanced the photoelectrochemistry and photocatalytic properties of the BiInOCl.