Pt-In₂O₃-SnO₂ Nanostructured Composite Photocatalyst Degradation Study On 2,4-dichlorophenol And Hydrogen Production Performance

With the development of human civilization and social progress,problems such as environmental pollution and energy shortages are currently major obstacles hindering the progress of society.At present,many organic compounds are used as intermediates to increase production in the industrial,agricultural and pharmaceutical industries.These organic compounds are generally difficult to degrade and are therefore directly discharged into rivers and lakes.As a result,environmental pollution problems such as eutrophication of water,excessive p H of water and excessive heavy metal content have increased year by year.At present,photocatalysis technology is an efficient method for degrading water pollutants without secondary pollution.On the one hand,it can degrade organic pollutants in water into inorganic CO₂ and H₂O.At the same time,part of the sewage can be converted into hydrogen energy,which can alleviate the current energy shortage problem.In this paper,2,4-dichlorophenol(2,4-DCP)as a representative refractory organic pollutant,was used for photocatalytic degradation.A batch of different types of photocatalysts composed of Sn,In,Pt and other elements were designed to improve the photocatalytic activity of the photocatalyst under visible light irradiation through modification in different ways.In addition,the photocatalytic hydrogen production performance of each photocatalyst in 2,4-DCP aqueous solution was also discussed.The main research contents are as follows:(1)The performance of Pt/Sn O₂ composite photocatalyst for photocatalytic degradation of2,4-DCP and photocatalytic hydrogen productionA wide-bandgap n-type semiconductor Sn O₂ was prepared as a support by a simple hydrothermal synthesis method,and noble metallic Pt with different loadings was loaded on the surface of the Sn O₂ support by photodeposition method to prepare a Pt/Sn O₂ composite light with good stability and non-toxic photocatalyst.The photocatalytic activity of the photocatalyst was evaluated by degrading 2,4-DCP under visible light.The experimental results show that when the noble metallic Pt loading was 5%and the solution p H was 6.5,the degradation of 2,4-DCP by the 5%Pt/Sn O₂ photocatalyst reaches 79.9%.In addition,while degrading 2,4-DCP,the photocatalytic hydrogen production efficiency at 5 hours was 1418.5?mol/g,which was 5.7times that of pure Sn O₂ support.(2)The performance of Pt/In₂O₃ composite photocatalyst for photocatalytic degradation of 2,4-DCP and photocatalytic hydrogen productionThe n-type semiconductor material In₂O₃ with a narrow band gap was prepared as a support by hydrothermal synthesis method,and the Pt/In₂O₃ photocatalyst was synthesized by loading the noble metallic Pt with different loading on the In₂O₃ support by photodeposition method.Through a series of characterization showed that when the loading of noble metallic Pt is 5%,the specific surface area of the 5%Pt/In₂O₃ photocatalyst reaches 20.7 m²/g,and the visible light absorption boundary increases to 633 nm,the recombination efficiency of photogenerated electrons and holes lowest.The experimental results of photocatalytic degradation of 2,4-DCP under visible light irradiation proved that loading 5%noble metallic Pt is beneficial to the photocatalytic activity,and when the p H of the solution was 7.5,the degradation efficiency of the 5%Pt/In₂O₃ photocatalyst reached 81.5%.In addition,while photocatalytic degradation of 2,4-dichlorophenol,the 5 hours photocatalytic hydrogen production efficiency of the 5%Pt/In₂O₃ photocatalyst reached 2841.3?mol/g,far exceeding the photocatalytic hydrogen production efficiency of pure In₂O₃ support.(3)The performance of Pt/In-Sn O₂defective photocatalytic composites for photocatalytic degradation of 2,4-DCP and photocatalytic hydrogen productionA simple hydrothermal synthesis method doped In ions into the Sn O₂ support to prepare an In-Sn O₂support material with abundant defect sites,and loaded the noble metallic Pt on the surface of the In-Sn O₂ support by photodeposition method.Through a series of characterization,it was proved that the doping of large size In ions replaced Sn ions in Sn O₂,which caused lattice distortion of In-Sn O₂,resulting in the generation of a large number of defect sites.These defects change the energy band structure of In-Sn O_2,which made the Pt/In-Sn O₂ defective photocatalyst can generate photogenerated electrons and holes more efficiently under visible light.Moreover,it can also increase the pollutants adsorption sites of the photocatalyst.Through the photocatalytic degradation activity of 2,4-DCP under visible light,Pt/In-Sn O₂ defective photocatalyst has the most excellent degradation effect,and the removal rate of 2,4-DCP in the solution reaches 89.2%after 180 minutes which is 1.47 times that of pure Sn O₂ support.In addition,in the photocatalytic hydrogen production test while degrading 2,4-DCP,the 5 hours photocatalytic hydrogen production efficiency of the Pt/In-Sn O₂ defective photocatalyst reached 3878.6?mol/g.And the photocatalytic hydrogen production rate is 775.72?mol/h g,which is 15.56 times that of pure Sn O₂ support.(4)The performance of Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst for photocatalytic degradation of 2,4-DCP and photocatalytic hydrogen productionA novel all-solid-state Pt-bridge Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst was prepared by an ingenious in situ deposition and photo-reduction protocol.The physicochemical properties of prepared materials were of the prepared materials were analyzed in depth via SEM,TEM,BET,DRS,XPS,PL and other characterization methods.It is revealed that the visible light absorption capacity of prepared composites was remarkably enhanced due to the localized surface plasma resonance effect of Pt nanoparticles.Moreover,such Pt nanoparticles act as the electron mediator of photogenerated carriers,and the photogenerated electron hole pairs of Sn O₂/Pt/In₂O₃ Z-scheme photocatalysts can be effectively separated,which hence reserving the most favorable reductive and oxidative reaction sites.The photocatalytic degradation efficiency of 2,4-DCP over Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst under visible light reaches 90%in 180min.In addition,while photocatalytic degradation of 2,4-DCP,the photocatalytic hydrogen production rate reached 967.018?mol/h g,higher than that of pure In₂O₃(103.358?mol/h g)and Sn O₂(49.847?mol/h g)by more than 9.36 and 19.40 times,respectively.In addition,the stability experiments showed that the photocatalytic hydrogen production rate of the Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst after five cycles has only decreased by 8.96%,indicating that Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst has good photocatalysis stability(5)The mechanism analysis of Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst for photocatalytic degradation of 2,4-dichlorophenol and photocatalytic hydrogen productionBy analyzing the degradation pathway of 2,4-DCP over Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst,the intermediate products of photocatalytic degradation of 2,4-DCP by superoxide radicals and hydroxyl radicals were studied,and through the total organic carbon(TOC)test,after 180 minutes of photocatalytic degradation,2,4-DCP was degraded into CO₂,H₂O,and small-molecule carbon-containing organic compounds.In addition,by constructing the energy band model of Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst,the mechanism of photocatalytic degradation of 2,4-DCP and photocatalytic hydrogen production over Sn O₂/Pt/In₂O₃ Z-scheme photocatalyst was obtained.This provides a theoretical basis for constructing a new type and high efficiency photocatalyst.