Modification Design Of Bismuth Oxycarbonate Nanotubes And Study Of Their Photocatalytic Performanc

With the development of industry,environmental pollution problems have attracted widespread attention.Photocatalytic technology has shown superior performance which can utilize clean solar energy to solve environmental pollution.However,many semiconductors have low light absorption efficiency and high carrier recombination efficiency,which can not be applied to real life.This work is devoted to investigating modification and photocatalytic performances of novel bismuth subcarbonate（Bi₂O₂CO₃,BOC）nanotubes catalysts,which mainly focuses on four aspects:first is the effect of Schottky junction on the photocatalytic performance of BOC;The second is the effect of multiple（ternary,binary）heterojunctions on the photocatalytic performance of BOC;Thirdly,the effect of halogen surface modification on the photocatalytic performance of BOC;Finally.the effect of sulfate radical cooperating with common active species（·OH,·O₂^-and h⁺）on the photocatalytic performance of BOC.（1）The novel hierarchical BOC nanotubes with thin nanosheet（～100 nm）assembly arrangement are prepared by simple hydrothermal method for the first time.Bi-BOC Schottky junctions are prepared by in-situ hydrothermal synthesis with Na H₂PO₂.After 90 minutes of UV irradiation,the degradation rate of Rh B by 0.5 Bi-BOC reaches 87%,and the photocatalytic performance is 3.8 times that of BOC.Bi nanoparticles modified on BOC nanotubes,which improves the separation efficiency of photogenerated carriers.In-situ deposition of Bi nanoparticles on semiconductors to improve photocatalytic performance is expected to be popularized and applied.（2）δ-Bi₂O₃/BOC heterojunction is prepared by calcining BOC nanotubes at low temperature.After UV light（λ<400 nm）irradiation,the photocatalytic performance of Rhodamine B（Rh B）is 5.4 times that of BOC.The significant improvement of photocatalytic performance is attributed to the reduction of recombination efficiency of photogenerated carriers after heterojunction formation.In addition,multiple heterojunctions are synthesized in-situ by Fe Cl₃ hydrothermal treatment BOC.0.8 Fe-BOC（BOC/Fe₂O₃/Bi OCl）and 1 Fe-BOC（Fe₂O₃/Bi OCl）are prepared when the addition amount of Fe Cl₃ is 0.8 mmol and 1 mmol,respectively.Under UV irradiation,the photocatalytic performance of 0.8 Fe-BOC and 1 Fe-BOC for the degradation of Rh B is 9.6 and 14.1 times that of BOC,respectively.After the formation of multiple heterojunctions,the charge transfer and separation efficiency are significantly improved.Low temperature calcination and in-situ hydrothermal preparation of heterojunctions are conducive to fabricating multiple heterojunctions with the obviously boosted photoactivity.（3）The effects of halogen surface modification on the photocatalytic performance of BOC are investigated by changing the concentration of halogen ions,reaction temperature and reaction time.Among the samples of halogen surface modified BOC,1M-150-Br-BOC shows best photocatalytic performance under ultraviolet light irradiation.The degradation activity is6.8 times higher than that of BOC.The improvement of photocatalytic performance is attributed to the halogen adsorbed on the BOC surface,which inhibits recombination of photogenerated electrons and holes,improves charge separation efficiency and reduces adsorption energy.This simple method of halogen surface modification can be extended to other photocatalysts.（4）The pre-adsorption of Na₂SO₄（Na₂SO₄-BOC）on BOC is performed at room temperature.SO₄^2-adsorbed on BOC surface can be excited by ultraviolet light,·OH and h⁺to form sulfate radicals（SO₄^-·）.The photocatalytic performance of Rh B by of Na₂SO₄-BOC is 12times that of BOC;Na₂SO₄ is directly added into BOC photocatalytic reaction system,the photocatalytic performance is 9 times that of BOC.The greatly enhanced photocatalytic activity is mainly attributed to the synergistic promotion of photocatalytic reaction by SO₄^-·,·OH and h⁺.SO₄^-·as an oxidation active species can be extended to other photocatalyst reaction systems.