The hysteresis loop changes of ferroelecric SrBi_2 Ta_2 O_9 (SBT) thin films(330nm) us the temperature of forming gas (5 percent hydrogen+95 percent nitrogen) annealing weremeasured when the annealing time was 1min an...The hysteresis loop changes of ferroelecric SrBi_2 Ta_2 O_9 (SBT) thin films(330nm) us the temperature of forming gas (5 percent hydrogen+95 percent nitrogen) annealing weremeasured when the annealing time was 1min and 10min. The selected annealing temperature was at 100deg C,200 deg C 250 deg C, 300 deg C, 350 deg C,400 deg C and 450 deg C, respectively. Our resultsshowed that the ferroelectric properties were easily destroyed and the leakage current changedabruptly when the SBT thin films were in their ferroelectric phase (<270 deg C). The space chargesat the grain boundary may take an important role' in absorption polarity molecular hydrogen when theSBT thin films were in the ferroelectric phase. The oxygen recovery experiments were also performedand investigated in this work.展开更多
Piezo-photocatalysis is an emerging photocatalytic technology in which the piezoelectric electric field drives photogenerated carriers to separate,thereby improving the photocatalytic activity of the catalyst.Herein,s...Piezo-photocatalysis is an emerging photocatalytic technology in which the piezoelectric electric field drives photogenerated carriers to separate,thereby improving the photocatalytic activity of the catalyst.Herein,solid phase and one-step molten salt processes were used to prepare SrBi_(2)Nb_(2)O_(9)(SBN)powders with granular and sheet morphologies,respectively.The influence of micromorphology on the piezo-photocatalytic performances of SBN was determined by degrading ciprofloxacin hydrochloride(CIP).SBN nanosheets demonstrate remarkable piezo-photocatalytic performance,achieving an 89.13%CIP degradation rate in 60 min and an apparent rate constant of 34.73×10^(-3) min^(-1).This performance is approximately 2.65 times higher than that of granular SBN and outperformed many recently reported piezo-photocatalysts under similar experimental conditions.Free radical trapping techniques,electron spin resonance spectroscopy and liquid chromatography-mass spectrometry are utilized to study the potential paths and mechanisms of CIP degradation.Piezoresponse force microscopy and finite element simulation show that the piezo-response of SBN nanosheets is significantly higher than that of granular SBN.SBN nanosheets achieve high degradation efficiency due to their optimized conduction band positions and enhanced piezoelectric effect,facilitated by the two-dimensional nanosheet structures.In this work,the piezoelectric internal electric field of piezoelectric catalysts can be increased by tuning the catalyst morphology,which points to a possible direction for the production of high-performance piezoelectric catalysts.展开更多
Antibiotics have received increasing attention due to their potential adverse effects on aquatic life and human health.How to efficiently degrade them into harmless substances is a challenging subject.Ferroelectric ma...Antibiotics have received increasing attention due to their potential adverse effects on aquatic life and human health.How to efficiently degrade them into harmless substances is a challenging subject.Ferroelectric materials with a built-in electric field can offer a strong separation ability for the photoinducedcharge pairs and are now found to be used as photocatalysts.Herein,a series of different morphologies of SrBi_(2)Ta_(2)O_(9)ferroelectric photocatalysts with high antibiotic degradation efficiency have been successfully synthesized through a molten salt method.With the addition of KCl,SrBi_(2)Ta_(2)O_(9)(SBTO 3)with exposed(001)facets shows the most excellent photocatalytic activity for decomposing tetracycline(TC)and ciprofloxacin(CIP)under visible light illumination(λ>420 nm).The rate constants of SBTO 3 for TC and CIP degradation are 1.38×10^(–1)and 4.54×10^(–2)min^(–1),which are 18 and 138 times that of the unmodified sample,respectively.The enhancement of photocatalytic performance is mainly attributed to the spontaneous polarization electric field along the[001]direction which provides a strong driven force for the separation of photoinduced charges.The KPFM results also confirm that the superior photocatalytic activity is consistent with the big large surface potential changes before and after light irradiation.The possible degradation pathways and intermediates of TC and CIP were well analyzed by DFT calculation and LC-MS.The results highlight that morphology control of the ferroelectric materials exhibits enhanced photocatalytic performance for the degradation of the antibiotic.展开更多
Photocatalysts with exposure of different crystal facets often show great differences in their photocatalytic activities due to differences in surface atomic arrangement and coordination.Thus,the actual photoreaction ...Photocatalysts with exposure of different crystal facets often show great differences in their photocatalytic activities due to differences in surface atomic arrangement and coordination.Thus,the actual photoreaction mechanism of a specific crystal facet in photocatalysis deserves to be explored.In this paper,as a case study,Sr Bi_(2)Ta_(2)O_(9)photocatalyst with preferential facet exposure was explored for the photocatalytic removal of NO at a ppb level.The efficiency of NO removal was remarkably improved by tuning the crystal exposure facet with high(200)facet exposure ratio.Optimized exposure of(200)crystal facet in Sr Bi_(2)Ta_(2)O_(9)(SBT)by thermal calcination at 800℃(SBT-800)leads to the highest NO removal activity of51%under a 300 W Xe lamp for 20 min;under visible light,SBT 800 achieves a 5-fold enhancement in NO removal efficiency compared to its counterpart,SBT-900.Active species capture experiments prove that the superoxide radical·O_(2)-is the main active species for the photocatalytic removal of NO,and surface selective deposition experiments conclude that(200)is the main electron-rich crystal plane,based on which the results of density functional theory(DFT)computation reveal the Bi O terminated nature of(001)crystal plane,where the models with both Bi O and Ta O terminated(001)planes were created and computated.Mechanistic study reveals that Sr Bi_(2)Ta_(2)O_(9)with a larger exposure of(200)facet provides more active reduction sites,thereby reducing more O_(2)to·O_(2)-,which further oxidizes the adsorbed NO to NO_(2)-/NO_(3)-.The present work underlines the role of facet tuning in the photoactivity modulation for NO removal photocatalytically.展开更多
基金This work sponsored by Motorola SPS Digital DNA Laboratories. It is also supported by a grant for State Key Program for Basic Research of China. We would like to thank Dr. Peir Y. Chu of Motorola SPS for his great help, useful advice and discussion.
文摘The hysteresis loop changes of ferroelecric SrBi_2 Ta_2 O_9 (SBT) thin films(330nm) us the temperature of forming gas (5 percent hydrogen+95 percent nitrogen) annealing weremeasured when the annealing time was 1min and 10min. The selected annealing temperature was at 100deg C,200 deg C 250 deg C, 300 deg C, 350 deg C,400 deg C and 450 deg C, respectively. Our resultsshowed that the ferroelectric properties were easily destroyed and the leakage current changedabruptly when the SBT thin films were in their ferroelectric phase (<270 deg C). The space chargesat the grain boundary may take an important role' in absorption polarity molecular hydrogen when theSBT thin films were in the ferroelectric phase. The oxygen recovery experiments were also performedand investigated in this work.
基金funded by the National Natural Science Foundation of China(22272057)Natural Science Foundation of Guangdong Province(2019A1515012129)Science and Technology Planning Project of Guangzhou City(202002030420).
文摘Piezo-photocatalysis is an emerging photocatalytic technology in which the piezoelectric electric field drives photogenerated carriers to separate,thereby improving the photocatalytic activity of the catalyst.Herein,solid phase and one-step molten salt processes were used to prepare SrBi_(2)Nb_(2)O_(9)(SBN)powders with granular and sheet morphologies,respectively.The influence of micromorphology on the piezo-photocatalytic performances of SBN was determined by degrading ciprofloxacin hydrochloride(CIP).SBN nanosheets demonstrate remarkable piezo-photocatalytic performance,achieving an 89.13%CIP degradation rate in 60 min and an apparent rate constant of 34.73×10^(-3) min^(-1).This performance is approximately 2.65 times higher than that of granular SBN and outperformed many recently reported piezo-photocatalysts under similar experimental conditions.Free radical trapping techniques,electron spin resonance spectroscopy and liquid chromatography-mass spectrometry are utilized to study the potential paths and mechanisms of CIP degradation.Piezoresponse force microscopy and finite element simulation show that the piezo-response of SBN nanosheets is significantly higher than that of granular SBN.SBN nanosheets achieve high degradation efficiency due to their optimized conduction band positions and enhanced piezoelectric effect,facilitated by the two-dimensional nanosheet structures.In this work,the piezoelectric internal electric field of piezoelectric catalysts can be increased by tuning the catalyst morphology,which points to a possible direction for the production of high-performance piezoelectric catalysts.
基金financially supported by the National Key Research and Development Project of China(No.2019YFC1803404)the National Natural Science Foundation of China(No.51772325)+3 种基金the Natural Science Foundation of Guangdong Province(Nos.2021A1515010375,2021A1515010390)the Excellent Young Talents Discipline Construction Project of Jinan University(No.2019QNGG19)the Fundamental Research Funds for the Central Universities(No.21621401)the Open Fund of Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications(No.2020B121201005)。
文摘Antibiotics have received increasing attention due to their potential adverse effects on aquatic life and human health.How to efficiently degrade them into harmless substances is a challenging subject.Ferroelectric materials with a built-in electric field can offer a strong separation ability for the photoinducedcharge pairs and are now found to be used as photocatalysts.Herein,a series of different morphologies of SrBi_(2)Ta_(2)O_(9)ferroelectric photocatalysts with high antibiotic degradation efficiency have been successfully synthesized through a molten salt method.With the addition of KCl,SrBi_(2)Ta_(2)O_(9)(SBTO 3)with exposed(001)facets shows the most excellent photocatalytic activity for decomposing tetracycline(TC)and ciprofloxacin(CIP)under visible light illumination(λ>420 nm).The rate constants of SBTO 3 for TC and CIP degradation are 1.38×10^(–1)and 4.54×10^(–2)min^(–1),which are 18 and 138 times that of the unmodified sample,respectively.The enhancement of photocatalytic performance is mainly attributed to the spontaneous polarization electric field along the[001]direction which provides a strong driven force for the separation of photoinduced charges.The KPFM results also confirm that the superior photocatalytic activity is consistent with the big large surface potential changes before and after light irradiation.The possible degradation pathways and intermediates of TC and CIP were well analyzed by DFT calculation and LC-MS.The results highlight that morphology control of the ferroelectric materials exhibits enhanced photocatalytic performance for the degradation of the antibiotic.
基金supported by the National Natural Science Foundation of China(Nos.21976116,52161145409)Shaanxi Science and Technology Program(No.2020KWZ-005)+3 种基金High Level Talents Introduction Project of"Pearl River Talent Plan"in Guangdong Province(No.2019CX01L308)the Support Scheme of Guangzhou for Leading Talents in Innovation and Entrepreneurship Funding(No.2016015)SAFEA of China(High-end Foreign Expert Project)Alexander-von-Humboldt Foundation of Germany(Group-Linkage Program)。
文摘Photocatalysts with exposure of different crystal facets often show great differences in their photocatalytic activities due to differences in surface atomic arrangement and coordination.Thus,the actual photoreaction mechanism of a specific crystal facet in photocatalysis deserves to be explored.In this paper,as a case study,Sr Bi_(2)Ta_(2)O_(9)photocatalyst with preferential facet exposure was explored for the photocatalytic removal of NO at a ppb level.The efficiency of NO removal was remarkably improved by tuning the crystal exposure facet with high(200)facet exposure ratio.Optimized exposure of(200)crystal facet in Sr Bi_(2)Ta_(2)O_(9)(SBT)by thermal calcination at 800℃(SBT-800)leads to the highest NO removal activity of51%under a 300 W Xe lamp for 20 min;under visible light,SBT 800 achieves a 5-fold enhancement in NO removal efficiency compared to its counterpart,SBT-900.Active species capture experiments prove that the superoxide radical·O_(2)-is the main active species for the photocatalytic removal of NO,and surface selective deposition experiments conclude that(200)is the main electron-rich crystal plane,based on which the results of density functional theory(DFT)computation reveal the Bi O terminated nature of(001)crystal plane,where the models with both Bi O and Ta O terminated(001)planes were created and computated.Mechanistic study reveals that Sr Bi_(2)Ta_(2)O_(9)with a larger exposure of(200)facet provides more active reduction sites,thereby reducing more O_(2)to·O_(2)-,which further oxidizes the adsorbed NO to NO_(2)-/NO_(3)-.The present work underlines the role of facet tuning in the photoactivity modulation for NO removal photocatalytically.
