Preparation Of Bismuth Vanadate Based Photocatalyst And Its Performance Study

Photocatalytic technology is widely used to solve water pollution problems due to its green and sustainable advantages,but the shortcomings of single photocatalysts such as low photogenerated carrier mobility and easy compounding,small photoresponse range and poor broad-spectrum degradability limit its practical application.To ameliorate these limitations,decahedral BiVO₄ monoclinic surface heterojunctions with double exposed（010）and（110）active crystal faces were prepared by modulating the growth rate of the crystal faces by H⁺ concentration,while Bi₂O₄/VmOn heterojunction photocatalysts were prepared by further upregulating the H⁺ concentration.Then,using BiVＯ4 surface heterojunction as the substrate,BiVO₄@BiOCl crystalline S-type and Z-type heterojunction and Cs_0.33WO₃/（t-m）-BiVO₄ double Z-type heterojunction photocatalysts were constructed,which effectively broadened the photoresponse range of photocatalysts,extended the charge lifetime,improved the carrier migration and separation efficiency,and achieved significantly enhanced fullspectrum broad-spectrum degradation performance of photothermal synergistic photocatalysis.The main findings are as follows:（1）The monoclinic phase of BiVO₄ with double exposed（110）and（010）crystalline planes was prepared by adjusting the H⁺concentration to preferentially grow the（110）crystalline planes of BiVO₄.further increasing the H⁺concentration to form HVO3·H⁺·NO₃^-and Bi（H2O）3（NO3）3,saturation precrystallization to V₂O₅ and Bi₂O₄ crystals,formation of V₂O₅·H⁺·NO₃^-groups,and then crystallized and reduced to VO2（B）crystals,and VO2（B）further generated VO2（B）·H⁺·NO₃^-groups,and the two gels reacted with each other to synthesize V6011 nuclei,and hydrothermal crystallization yielded Bi₂O₄/VmOn heterojunction composed of Bi₂O₄,V₂O₅,VO2（B）and V6O11.The heterojunction,the large number of oxygen vacancies contained in the system and the small polariton leap of V6O11 were utilized to achieve 96.41%/96.90%degradation of TC by the Bi₂O₄/VmOnheterojunction after 90 min of direct visible/near-infrared light irradiation with the presence of enhanced dark catalytic ability,and the degradation of TC by its reaction under dark light for 120 min reached 98.56%.（2）A photo-deposited crystal plane selectively induce method was used to nucleate strong reduction-capable BiOCl on BiVO₄（010）crystal planes in heterogeneous phase and OVs-BiOCl on BiVO₄（110）crystal planes in homogeneous phase.The core-shell BiVO₄@BiOCl crystal plane S-type and Ztype heterojunction photocatalysts were prepared.Under the synergistic effects of surface heterojunction built-in electric field,interfacial electrostatic built-in electric field,inter-heterojunction polarization charge transfer and LSPR effect of oxygen vacancies,BiVO₄@BiOCl exhibit strong broad-spectrum degradation ability over the entire spectral range.The degradation rates of BiVO₄@BiOCl for TC were 90.32%/71.17%,degradation efficiency of CIP,BHA,Phenol,BPA and Coumarin were 49.36～71.32%/37.88%～62.86%,respectively,after Vis/NIR light.It also showed good degradation performance for mixed antibiotic.（3）The photothermal effect of Cs_0.33WO₃ was used to change the（110）crystalline phase of the monoclinic phase m-BiVO₄ to the tetragonal phase tBiVO₄,forming the exposed（010）crystalline m-BiVO₄/t-BiVO₄,and then the negatively charged Cs_0.33WO₃ was loaded on t-BiVO₄ by photodeposition,further forming the Cs_0.33WO₃/（m-t）-BiVO₄ double-Z heterojunction photocatalyst.The formation of the double Z-type heterojunction under the effect of electrostatic gravity and built-in electric field grows the carrier charge transfer path,prolongs the e-life,and enhances the photocatalytic activity with full spectral response.The small polariton jumping effect of W5+/W6+in Cs_0.33WO₃ crystals,where e’ escapes to the adjacent W site and radiates energy as phonons,increases the temperature of the liquid-phase reaction system by 18.5℃ and 24.9℃ in the visible/NIR,respectively,and the photothermal synergy accelerates and enhances the degradation catalytic activity of Cs_0.33WO₃/（m-t）-BiVO₄ heterojunctions.The degradation rates of 40 mg/L TC were 90.49%/91.94%after 180 min irradiation under visible/near-infrared light,which were 1.95/5.22,1.68/1.65 and 1.24/1.29 times higher than those of m-BiVO₄,Cs_0.33WO₃ and（m-t）-BiVO₄,respectively.