Investigation On The Photocatalytic Properties And Structure Regulation Of Vanadate Nanomaterials

With the development of industrial society,water pollution has become an increasingly serious problem,and hard-to-degrade pollutants such as industrial dyes,heavy metal ions and antibiotics are a serious threat to human health and life safety.Semiconductor photocatalysis technology has been widely used in environmental remediation,including water treatment,air purification and antimicrobial therapy,due to its high activity,low cost and environmental friendliness.Among the many semiconductor materials,bismuth vanadate（BiVO₄）has received widespread attention in recent years due to its suitable band gap,stable chemical properties and safety and non-toxicity.However,single-phase BiVO₄ still faces problems such as severe photogenerated carrier compounding and difficulty in balancing light absorption efficiency and redox potential.In this thesis,based on BiVO₄ photocatalytic materials,BiVO₄ nanodendrites were hydrothermally prepared,and multifaceted BiVO₄ heterojunction photocatalysts were prepared by introducing oxygen vacancies,forming Z-type heterojunctions,constructing core-shell structures and introducing noble metal modifications through defect engineering,and achieving significant improvement in the degradation capacity of organic pollutants.The microstructure,chemical state,photodegradation and photoelectrochemical properties of the photocatalysts were systematically studied,and the energy band structure,active radicals and photocatalytic performance changes corresponding to the microstructure were analysed to reveal the photocatalytic mechanism of the organic degradation process.The details are as follows:（1）BiVO₄/OVs/g-C₃N₄ structured Z-type heterojunction photocatalysts were synthesized by acoustochemical introduction of oxygen vacancies（OVs）,and the successful introduction of OVs was confirmed by paramagnetic spin resonance spectroscopy（EPR）.Among the prepared composite photocatalysts,the BiVO₄/OVs/g-C₃N₄ photocatalyst sample with the most optimized performance could degrade 20 mg/L of rhodamine B（Rh B）and 10 mg/L of tetracycline（TCs）within 12 min and 9 min,respectively.The linear polarization curve（LSV）and photocurrent response curve（IT）obtained from electrochemical tests showed that the photocurrent density of 1μA/cm²（0V vs.Ag/Ag Cl）was enhanced by 6 times compared to monomeric BiVO₄.The hydrogen production test results show that the BiVO₄/OVs/g-C₃N₄ photocatalyst has double the hydrogen production efficiency（558.3μmol/g/h）compared to monolithic g-C₃N₄（307μmol/g/h）.Based on the results of active radical testing and energy band structure characterization,the BiVO₄/OVs/g-C₃N₄ photocatalyst was confirmed to be a Z-type heterojunction structure,which achieved the spatial separation of photogenerated carriers and the increase of redox potential,and finally realized the comprehensive improvement of photocatalytic performance.（2）The ternary Ag@AgBr/BiVO₄ photocatalyst was synthesized by a two-step method,and the in situ growth of Ag nanoparticles on the BiVO₄/AgBr core-shell structure was confirmed by high transmission electron microscopy（HRTEM）.Among the prepared composite catalysts,Ag@AgBr/BiVO₄ with optimized performance could degrade 20 mg/L of rhodamine B（Rh B）and 10 mg/L of tetracyclines（TCs）within 16min and 20 min,respectively.The photocurrent density was 2.5μA/cm²（0 V vs.Ag/Ag Cl）,a 15.7-fold enhancement over monomeric BiVO₄.Based on the UV-vis absorption spectra,the local plasmon resonance（LSPR）effect of Ag was demonstrated to extend the absorption range of visible light;the results of active radical testing and energy band structure characterisation revealed that the core-shell structure under this system is capable of spatially separating photogenerated carriers,and the high energy level electrons generated by Ag nanoparticles provide additional superoxide radicals,ultimately achieving a synergistic multi-pathway photocatalytic performance enhancement.Figure[31]Table[4]Reference[124]...