Study On Combustion Synthesis Of Bismuth-rich Bismuth Oxyhalide And Its Performance And Mechanism Of Photodegradation Of Pollutants

Although our living conditions have been greatly improved,environmental and energy issues still plague mankind.With people’s efforts,in recent years,photocatalytic technology centered on semiconductors has shown great advantages and good prospects.As an important semiconductor photocatalyst material,bismuth oxyhalide（Bi OX,X=F,Cl,Br,I）compound because of its unique layered structure,its large built-in electric field and asymmetric polarization effect,which improves the separation efficiency of charges and has a suitable energy band position.Therefore,we selected the bismuth-rich Bi_xO_yBr_zphotocatalyst as the research object,which have better effect and with visible light response.First of all,in this paper,four Bi₃O₄Br with different surface oxygen vacancies（OVs）contents were synthesized by the self-combustion method of ionic liquid by adjusting the amount of reaction raw materials.On this basis,the influence of OVs on their surface was studied by studying the transfer of electrons on the surface of the four samples,the generation of photogenerated carriers,and the electron-hole recombination.Through electron spin-resonance spectroscopy（ESR）,the content of OVs and the content of free radicals generated by the catalyst in the solution were determined,and the activation of molecular oxygen by OVs was studied.By studying their ability to degrade Rhodamine B,the effect of OVs on the catalytic oxidation ability was determined.Then,we used ionic liquid self-combustion method synthesized Bi₂₄O₃₁Br₁₀ with different ratios of{213}/{117}facets by adjusting the ratio of reaction raw materials.To study the effect of exposed crystal facets of Bi-rich photocatalyst on Bi₂₄O₃₁Br₁₀.XRD,FE-SEM and HRTEM patterns show the morphology and structure,surface photovoltage（SPV）,time-resolved fluorescence（TRPL）,electrochemical impedance spectroscopy（EIS）and photocurrent decay spectroscopy were used to determine the separation efficiency of photogenerated electrons and holes,UV-Vis Diffuse reflectance spectroscopy（UV-Vis DRS）,Mott-Schottky curve illustrates their band gap and energy band location.The adsorption of oxygen on{213}and{117}crystal facets was calculated by density functional theory（DFT）method.In the visible light and scavenger experiments,the photocatalytic mechanism and active species produced in the photocatalytic process were studied through the degradation of Rhodamine B（Rh B）.The results show that although the main exposed{213}crystal facete has strong molecular oxygen adsorption capacity,the preferential growth of the secondary{117}crystal plane in Bi₂₄O₃₁Br₁₀ as the dominant crystal plane will lead to higher separation efficiency and higher degradation ability.This shows that the separation efficiency of charge carriers plays a more important role than oxygen adsorption performance in generating active oxygen and enhancing photocatalytic activity.