| Sodium bismuth titanate-barium titanate(BNBT)nanofibers have attracted extensive attention in the field of wastewater treatment because of their high piezoelectric properties and specific surface area.Under the external stress,BNBT nanofibers deform to produce electrons and holes,and then generate free radicals with redox ability to realize the degradation of organic pollutants in sewage.However,the high electron hole recombination rate limits its piezoelectric catalytic performance.The noble metal/piezoelectric interface formed by modifying the piezoelectric catalyst can promote the charge transfer at the interface and reduce the electron hole recombination rate.At present,the mechanism of piezoelectric catalytic degradation of piezoelectric materials and precious metals in different composite forms is not clear.Therefore,in this study,three kinds of composite nanofibers with different structures were prepared by using electrospinning technology and photo thermal reduction technology by changing the composite form of BNBT and Ag in the fiber.The effects of preparation process(electrospinning parameters,calcination temperature,etc.)on the morphology of BNBT fiber were studied.The effects of Ag content,ultrasonic power and the composite form of BNBT and Ag on the piezoelectric photocatalysis performance were analyzed,and the mechanism of piezoelectric catalysis and piezoelectric photocatalysis was clarified.The main results are as follows:(1)Ag(Ⅰ)/BNBT composite nano fibers of BNBT homogeneous composite Ag were prepared by electrospinning/thermal reduction method.Under ultrasonic driving,the Schottky barrier formed at the contact interface between precious metals and semiconductors,as well as the alternating piezoelectric field,reduce the electron hole recombination rate and improve the piezoelectric catalytic degradation performance.When the addition of Ag(Ⅰ)was 1%,the piezoelectric catalytic degradation efficiency and degradation rate of RhB dyes by Ag(Ⅰ)/BNBT-1 composite nanofibers under the driving of 100 W ultrasonic power reached 59.1%and 1.15×102 min-1,compared to BNBT fiber(33.2%,4.76×10-3 min-1)increased by 78%and 141.6%respectively.(2)BNBT/Ag(S)composite nanofibers loaded with Ag on the surface of BNBT were prepared by electrospinning/photochemical reduction.The average size of Ag(S)nanoparticles is about 8.2 nm.Under ultrasonic vibration and UV irradiation,Ag(S)nanoparticles on the surface can not only enhance light absorption through surface plasma effect,but also act as a "fast channel" for photogenerated carrier transfer to improve the performance of piezoelectric photocatalytic degradation.When the Ag(S)loading was 1%,the piezo-photocatalytic degradation efficiency(97.7%)and degradation rate(4.65%×10-2 min-1)of RhB dye by BNBT/Ag(S)-1 composite nanofibers was significantly higher than that of Ag(Ⅰ)/BNBT-1 composite nanofibers(82.2%,2.15×10-2 min-1).After five piezoelectric photocatalysis cycles,the degradation efficiency of RhB dye by BNBT/Ag(S)composite nanofibers was still as high as 88.7%.(3)Ag(Ⅰ)/BNBT/Ag(S)composite nanofibers loaded with Ag inside and outside BNBT were prepared by electrospinning/photo-thermal reduction method.The composite Ag(Ⅰ)and loaded Ag(S)increase the contact interface with the matrix fiber BNBT,promote the interface electron transfer,reduce the carrier recombination rate,and improve the piezoelectric photocatalytic degradation rate.When Ag(S)doping amount and Ag(S)loading amount both 1%,the piezophotocatalytic properties of Ag(Ⅰ)/BNBT/Ag(S)-1 composite nanofibers(99.04%,5.74%×10-2 min1)was significantly higher than Ag(Ⅰ)/BNBT-1(82.2%,2.15 ×10-2 min-1)composite nanofibers and BNBT/Ag(S)-1(97.7%,4.65×10-2 min-1)composite nanofibers. |
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