Construction Of Non-precious Metal/Polyoxometalate Doped TiO₂ Composite Catalyst System And Its Photocatalytic Performance

In view of the increasingly serious energy crisis and environmental pollution,semiconductor photocatalysis technology is an important means to realize the efficient conversion of solar energy and restore the environment.TiO₂ is a relatively ideal photocatalytic material.Its advantages are non-toxic and harmless,low price,high photocatalytic activity and good stability.In contrast,TiO₂ has a band gap of about 3.2 e V and can only utilize 5 percent of the ultraviolet part of the solar spectrum.At the same time,TiO₂ photogenerated carrier is easy to recombine,and the quantum efficiency is low.These factors limit the practical application of TiO₂.Therefore,TiO₂ photocatalytic materials were modified and improved to expand the spectrum absorption range and improve the photogenerated carrier separation efficiency.The research on a new stable and efficient visible light catalyst has gradually become the focus in the field of photocatalysis.Herein,a series of Bi nanoparticles/polyoxometalate[H₃PMo₁₂O₄₀](PMo₁₂)doped TiO₂composites were prepared by simple electrospinning/calcination technology combined with hydrothermal method.,which was labelled as x wt%Bi/PMo₁₂ doped TiO₂（abbr.x%Bi/PT,x=10,20 and 30,respectively）.In the composite material,polyoxometalate PMo₁₂ as dopant reduces the band gap value of TiO₂,effectively expands its visible light absorption,and enhances its photocatalytic redox ability.Moreover,the Schottky junction between Bi NPs and PT further promotes the separation efficiency of the photoinduced carriers.Therefore,these as-prepared catalysts demonstrated outstanding and persistent photocatalytic activity for removing tetracycline（TC）,enrofloxacin（EFA）and methyl orange（MO）with visible-light（λ>420 nm）illumination.Especially,20%Bi/PT specimen presented the optimal catalytic performance,whose degradation efficiencies for TC,EFA and MO reached 86.0%,90.9%and 92.5%,respectively.At the same time,we studied the influencing factors of photocatalytic TC degradation in detail,including the amount of catalyst,TC concentration,p H value of solution,reaction temperature,inorganic anions and water quality.The superoxide radical（·O₂^-）,hydroxyl radical（·OH）and holes（h⁺）were proved to be the dominating active species in contaminants degradation through the trapping tests and electron spin resonance（ESR）measurements.Furthermore,the possible TC degradation pathways were established based on the identification of degradation products by high performance liquid chromatography-mass spectrometry（HPLC-MS）.The toxicity of intermediates was also assessed through QSAR prediction.According to the energy band structure analysis,the corresponding photocatalytic mechanism was revealed.The current work provides several new insights for the design and preparation of low cost,efficient,stable and versatile photocatalysts.