Synthesis Of Novel Bi-based Catalysts And Its Purification Performance For Environmental Pollutants

In this paper,two aspects are mainly studied.One is the photocatalytic degradation of methyl orange dye?MO?wastewater by a novel Bi-based catalyst??BiO?₂OHCl?with containing internal electric field.The other is the controllable morphology of BiOF nanosheets and its photocatalytic activity for the degradation of rhodamine B dye?RhB?.?1?In this work,bismuth oxychloride??BiO?₂OHCl?is prepared by a simple precipitation method,and the effect of mixed anion layer on the photochemical properties is mainly investigated.The sample is characterized by polycrystalline X-ray powder diffraction?XRD?,scanning electron microscope?SEM?,infrared spectroscopy?IR?,high-resolution transmission electron microscope?HRTEM?,selection area electron diffusion?SAED?,UV�visible diffuse reflectance spectra?UV-DRS?,photoluminescence fluorescence?PL?,etc.It is found that under ultraviolet light irradiation???400 nm?,the photoactivity of?BiO?₂OHCl is 1.8 times higher than that of BiOCl for the degradation of MO,although?BiO?₂OHCl has a much lower BET area(3.4 m²g^-1)than BiOCl(15.9 m²g^-1).Comparing?BiO?₂OHCl with BiOCl,parts of Cl in the anion layer of BiOCl are replaced by hydroxyl.The mixed anion layer has shifted the energy bands down,compared with BiOCl.Because hydroxyl has a higher ability to attract electron than Cl,the insertion of OH^-has greatly increased the electron density of the anion layer of?BiO?₂OHCl.Thus,the internal electric field?IEF?of?BiO?₂OHCl has been strengthened,which is firmly demonstrated by the photocurrent results.The strengthened IEF could favor for the separation and transfer of photogenerated charges,leading to an improved photoactivity.This study provides a new idea to develop the efficient photocatalysts through building mixed anion layer.?2?So far,BiOF nanosheets exposed with{101}facets have not been reported.In this work,BiOF mainly exposed with{101}facets,instead of common{001}facets,are prepared by a simple hydrothermal method at different pH values.It is interesting that BiOF thick rectangular plates and thin round nanosheets are formed through the growth preferential along[001]and[101]directions,respectively.On base of layered crystallography structure,the preferential growth along[001]direction favors to form a thick multi-layered structure,whereas thin fewer-layered structure for the preferential growth along[101]direction.Moreover,more surface oxygen vacancies are contained in thin nanosheets,which reduces the band gap and improves charge transfer and separation.As a result,BiOF round nanosheets show an activity7.9 times higher than rectangular plates for the degradation of rhodamine B?RhB?under ultraviolet light irradiation???400 nm?.