Controllable Preparation Of Sulfur-Doped Bismuth Oxychloride And Photocatalytic Degradation Of Pollu-Tants

Bismuth oxychloride(BiOCl)crystals have the advantages of unique layered structure,high potential,simple preparation process,rich raw material sources,and low price,and have shown good application prospects in the field of photocatalytic degradation of organic pollutants.However,it can only be excited by ultraviolet light with a wavelength of 300 to 400 nm(about 5%of the solar spectral energy),and has a relatively poor response to visible light with a wavelength of 420 to 700 nm(about 43%of the solar spectral energy),which limits the practical application of BiOCl photocatalytic materials.To this end,the academic community proposes strategies such as doping heterogeneous elements in the BiOCl lattice or modifying their surfaces to solve the above problems.Theoretically,the introduction of S element into the BiOCl lattice can not only enhance the utilization of visible light,but also form impurity energy levels that can promote photogenerated carrier separation.Therefore,it is proposed to enhance the performance of Sdoped BiOCl photocatalytic degradation of organics by constructing oxygen vacancies and surface hydroxylation,reveal the physical mechanism of multi-defect coordination to enhance photocatalytic performance,and provide certain theoretical guidance for the construction of new BiOCl-based composite photocatalytic materials.The main research results of this paper are as follows:(1)S-doped BiOCl(denoted as BOC-S-OH)photocatalysts containing oxygen vacancies and surface hydroxylation modifications were successfully prepared in the Bi(NO3)3/NaCl/NaOH/H2O system by a pot of hydrothermal method.Visible light catalytic degradation of rhodamine B(RhB)and tetracycline hydrochloride(TCH)showed that:in the photocatalytic degradation of RhB,the kinetic constant k value of BOC-S-OH is about 93.7 times that of BOC,and in the photocatalytic degradation of TCH,the k value of BOC-S-OH is about 7 times that of BOC.Free radical capture experiments have shown that in the process of RhB and TCH photocatalytic degradation,·O2-is the active substance that plays a major role.After normalizing the kinetic constant k-value to BET specific surface area(denoted as k’),the k’ values of both RhB and TCH of BOC-S-OH degradation are 4 times that of BOC.The improvement of the photocatalytic degradation of organic matter in BOC-S-OH samples is attributed to the fact that the introduction of impurity energy levels by S doping enhances the visible light utilization rate and the bulk photogenerated carrier separation efficiency,as well as the synergistic enhancement of surface oxygen vacancies and surface hydroxylation on light absorption and surface photogenerated carrier separation efficiency.(2)S-doped BiOCl(denoted as BOC261)photocatalysts with surface hydroxylation was successfully prepared in the BiCl3/NaOH/H2O system by a pot of hydrothermal method.The results of visible photocatalytic degradation TCH show that the kinetic constant k value of BOC261 is about 15 times that of BOC.Free radical capture experiments have shown that in the photocatalytic degradation process of TCH,·OH is the active substance that plays a major role.After normalizing the kinetic constant k-value to BET specific surface area(denoted as k’),the k’value of BOC261 is about 2.5 times and 5 times that of BOC2 and BOC61,and BOC261 still shows more excellent photocatalytic degradation TCH performance.The improvement of the photocatalytic degradation of organic matter in BOC261 samples is attributed to the fact that surface hydroxylation and S doping synergistically enhance the photocatalytic performance of BiOCl,that is,surface hydroxylation and S element doping lead to impurity energy levels in surface vacancies and lattices,which not only increases the visible light absorption of BOC261 samples,but also jointly improves the separation and transmission efficiency of bulk phase and surface photogenerated carriers.