Preparation And Catalytic Performance Of Micro/Nano Piezoelectric Composites

With the developing of industrial society,the problems of environmental pollution,especially water pollution has become increasingly serious.The technology of catalysis is an environmental,effective,and economic method for water treatment.Photocatalysis was the first to be invetigsted and applied technology,its efficiency is vastly limited by the recombination of photo-induced carriers.As the technology of being able to convert the mechanical energy to chemical energy,piezocatalysis could use the built-in electric field to promote separation and transfer of carriers,thus to siginificantly improve the catalytic efficiency.This work proposes several schemes to apply the piezoelectric field to improve the catalytic efficiency of materials.This work takes nano/microscale BNT and PMN-PT as the research objects,to explore their synthesis scheme,and to prepare different composites and investigate their catalytic performance.The main research contents and conclusions are as follows:(1)BNT nano materials were synthesized by hydrothermal method.The perovskite monoclinic BNT spherical nanoparticles of uniform size were obtained after 48 h of reaction at a concentration of 10 M of mineralizer and temperature of 180?.The influence of every reaction conditions on the synthesis of BNT nanowires was investigated and the conculsion was that the perovskite monoclinic nanowires with pure phase and large length to diameter ratio can be obtained after 48 h reaction at a concentration of 12 M of mineralizer,temeperature of 180?and ritring speed of 800 rpm.(2)BNT@TiO₂ and BNT-BiOBr nanocomposites were respectively prepared by sol-gel and hydrothermal method.The performance of piezo-photocatalysis of the former and polar-enhanced photocatalysis of the latter was investigated.Under the irradiation of ultrasonic vibration(40 KHz,100 W)and visible light(?>420 nm,300 W),the degradation ratio of Rh B solution(50 ml,10 mg/l)after 90 min by the BNT@TiO₂ compcoite reached93%,which was 83%and 28%higher than that of piezocatalysis and photocatalysis,respectively.The degradation ratio after 150 min of Rh B solution(50 ml,5 mg/l)through piezo-photocatalytic effect of the BNT@TiO₂/PVDF porous film reached 95%,the degradation ratio after four-cycle experiments reached 66%.The photocatalytic efficiency of the BNT-BiOBr composite under visible light was significantly enhanced compared with pure BiOBr,its degradation ratio after 60 min reached 81%.The photocatalytic efficiency of polarized BNT-BiOBr was further improved,which can completely degrade the Rh B solution in same time,indicating that the polarization field can greatly promote the separation and transmission of photo-generated carriers.(3)The perovskite PMN-PT materials were synthesized by the molten-salt and hydrothermal method,and PMN-PT-group composites were prepared to study their catalytic performance.As a result,the most abundant monoclinic perovskite PMN-PT nanowires were obtained after 27 h of reaction at concentration of 0.82 g/l of PAA and 6 mol/l of KOH and at the temperature of 235?.In 120 min,the degradation ratio Rh B solution(10 mg/l,100 ml)through the piezo-photocatalytic effect of PMN-PT@TiO₂ composite reached 40%.In 150min,the degradation ratio of Rh B solution(5 mg/l,50 ml)through the piezocatalytic effect of PMN-PT/PVDF porous film reached 60%,the film only lost 21%of its weight and maintained a degradation ratio of 47%after four-cycle degradation experiments.It indicates that the porous film was a catalytic material not only could maintain a certain catalytic stability,but slao could effectively reduce the occurrence of secondary pollution.