As an intense picosecond laser pulse irradiates a hydrocarbon target,the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target.We investigate the effect of the lase...As an intense picosecond laser pulse irradiates a hydrocarbon target,the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target.We investigate the effect of the laser and hydrocarbon target parameters on proton acceleration with two/threedimensional particle-in-cell simulations.It is found that the resulting two-ion species plasma can generate a multiple peaked charge-separation field that accelerates the protons.In particular,a smaller carbon-to-hydrogen ratio,as well as the thinner and/or lower density of the target,leads to a larger sheath field and thus proton beams with a larger cutoff energy and smoother energy spectrum.These results may be useful in achieving high-flux quasi-monoenergetic proton beams by properly designing the hydrocarbon target.展开更多
Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separati...Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separation.Therefore,investigating highly effective COF-based photocatalysts is crucial.For the first time,conjugated COF/perylene diimide urea polymer(PUP)all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF(denoted as TATF-COF)with PUP.The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h^(-1) g^(-1) for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts,resulting in an apparent quantum efficiency of up to 19.7%at 420 nm.The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H_(2) evolution.Experiments and theoretical studies reveal plausible H_(2) evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation.This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.展开更多
A charge carrier mobility of polymer films with the time-of-flight(TOF) technique using a fullerene layer was measured and the TOF photocurrent waveform can be remarkably improved.The 80-nm-thick fullerene layer is fu...A charge carrier mobility of polymer films with the time-of-flight(TOF) technique using a fullerene layer was measured and the TOF photocurrent waveform can be remarkably improved.The 80-nm-thick fullerene layer is functioned as a charge-separation layer(CSL) which was placed between ITO electrode and the polymer layer of MEH-PPV(poly[2-methoxy-5-(2'-ethylhexyloxy) 1,4-phenylenevinylene]).In the CSL,the photo-generated holes and electrons can be efficiently separated,resulting in an enhanced current signal and great improvement of TOF waveform.The sample structure with fullerene layer exhibits a great advantage to measure the hole mobilities of polymers with low energy band gap.展开更多
本文将雷暴云的起电、放电物理过程引入中尺度的WRF(Weather Research and Forecasting)模式,并对超级单体和飑线过程进行了模拟研究。起电过程在Milbrandt双参数微物理方案中写入,包含霰、雹与冰晶、雪之间的非感应起电机制,以及霰、...本文将雷暴云的起电、放电物理过程引入中尺度的WRF(Weather Research and Forecasting)模式,并对超级单体和飑线过程进行了模拟研究。起电过程在Milbrandt双参数微物理方案中写入,包含霰、雹与冰晶、雪之间的非感应起电机制,以及霰、雹与云滴之间的感应起电机制。放电参数化方案只考虑了闪电的整体效应。对一次超级单体的模拟结果表明,电荷结构呈现正、负、正的三极性结构,主正电荷区在-40℃到-60℃之间,主负电荷区在-10℃到-30℃之间,下部正电荷区在零度层附近,总电荷浓度最大值接近2nC/m3。这种电荷结构的垂直分布同以往在强对流天气系统中观测到的典型电荷结构一致。对飑线过程的模拟结果表明,部分单体电荷结构呈现出反的偶极性且飑线中最大电荷浓度小于超级单体。在飑线成熟阶段,模拟得到的闪电分布与观测的地闪活动在分布型上相似。展开更多
Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalys...Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.展开更多
Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolu...Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolution and benzaldehyde production by dehydrogenation of benzyl alcohol over Nidecorated Zn_(0.5)Cd_(0.5)S solid solution under visible light. The photocatalytic system shows an excellent hydrogen production rate of 666.3 μmol h^(-1) with high stability. The optimal apparent quantum yield of52.5% is obtained at 420 nm. This noble-metal-free photocatalytic system displays much higher activity than pure Zn_(0.5)Cd_(0.5)S and Pt-loaded Zn_(0.5)Cd_(0.5)S solid solution. Further studies reveal that the metallic Ni nanocrystals play an important role in accelerating the separation of photogenerated charge carriers and the subsequent cleavage of α-C–H bond during dehydrogenation of benzyl alcohol.展开更多
Developing low-cost and high-efficiency photocatalysts for hydrogen production from solar water splitting is intriguing but challenging. In this study, unique one-dimensional （1D） multi-node MoS2/CdS hetero-nanowir...Developing low-cost and high-efficiency photocatalysts for hydrogen production from solar water splitting is intriguing but challenging. In this study, unique one-dimensional （1D） multi-node MoS2/CdS hetero-nanowires （NWs） for efficient visible-light photocatalytic H2 evolution are synthesized via a facile hydrothermal method. Flower-like sheaths are assembled from numerous_ defect-rich O-incorporated {0001} MoS2 facet surrounded CdS NW stems are ultrathin nanosheets （NSs）, and {1120}- grown preferentially along the c-axis. Interestingly, the defects in the MoS2 NSs provide additional active S atoms on the exposed edge sites, and the incorporation of O reduces the energy barrier for H2 evolution and increases the electric conductivity of the MoS2 NSs. Moreover, the recombination of photoinduced charge carriers is significantly inhibited by the heterojunction formed between the MoS2 NSs and CdS NWs. Therefore, in the absence of noble metals as co-catalysts, the 1D MoS2 NS/CdS NW hybrids exhibit an excellent H2-generation rate of 10.85 mmol·g^-1·h^-1 and a quantum yield of 22.0% at ,λ = 475 nm, which is far better than those of Pt/CdS NWs, pure MoS2 NSs, and CdS NWs as well as their physical mixtures. Our results contribute to the rational construction of highly reactive nanostructures for various catalytic applications.展开更多
Constructing a Z-scheme is a significant approach to improve the separation of photogene rated carriers for effective organic pollutant degradation.Herein,a BiVO4/ZnIn2S4(BZ) Z-scheme composite was successfully synthe...Constructing a Z-scheme is a significant approach to improve the separation of photogene rated carriers for effective organic pollutant degradation.Herein,a BiVO4/ZnIn2S4(BZ) Z-scheme composite was successfully synthesized,and applied to photodegrade methyl orange(MO) irradiated by a LED lamp.Anchoring the BiVO4 on the ZnIn2S4 nanoparticles promoted the separation of photogenerated electronholes and broadened the light response range.The detailed characterizations,including surface morphology,elements valence state,and photocurrent performance,demonstrated that the enhanced separation of photogenerated carriers was the pivotal reason for the enhanced photocatalysis reaction.Benefiting from the excellent photocatalytic characteristics,the 5% mass ratio of BZ composite presented the highest MO degradation rate of 0.00997 min^-1,which was 1.9 and 10.3 times greater than the virgin ZnIn2S4 and BiVO4,respectively.Furthermore,the BZ hybrid materials indicated a well photo-stability in the four recycling tests.展开更多
A three-dimensional（3D） charging-discharging cloud resolution model was used to investigate the impact of the vertical velocity field on the charging processes and the formation of charge structure in a strong thund...A three-dimensional（3D） charging-discharging cloud resolution model was used to investigate the impact of the vertical velocity field on the charging processes and the formation of charge structure in a strong thunderstorm. The distribution and evolution of ice particle content and charges on ice particles were analyzed in different vertical velocity fields. The results show that the ice particles in the vertical velocity range from 1 to 5 m s-1obtained the most charge through charging processes during the lifetime of the thunderstorm. The magnitude of the charges could reach 1014 n C. Before the beginning of lightning activity,the charges produced in updraft region 2（updraft speed 13 m s-1） and updraft region 1（updraft speed between 5 and 13 m s-1） were relatively significant. The magnitudes of charge reached 1013 n C, which clearly impacted upon the early lightning activity. The vertical velocity conditions in the quasi-steady region（updraft speed between -1 and 1 m s-1） were the most conducive for charge separation on ice particles on different scales. Accordingly, a net charge structure always appeared in the quasi-steady and adjacent regions. Based on the results, a conceptual model of ice particle charging, charge separation, and charge structure formation in the flow field was constructed. The model helps to explain observations of the＂lightning hole＂ phenomenon.展开更多
基金the National Key R&D Program of China(No.2016YFA0401100)National Natural Science Foundation of China(Nos.12175154,11875092,and 12005149)+1 种基金the Natural Science Foundation of Top Talent of SZTU(Nos.2019010801001 and 2019020801001)The EPOCH code is used under UK EPSRC contract(EP/G055165/1 and EP/G056803/1).
文摘As an intense picosecond laser pulse irradiates a hydrocarbon target,the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target.We investigate the effect of the laser and hydrocarbon target parameters on proton acceleration with two/threedimensional particle-in-cell simulations.It is found that the resulting two-ion species plasma can generate a multiple peaked charge-separation field that accelerates the protons.In particular,a smaller carbon-to-hydrogen ratio,as well as the thinner and/or lower density of the target,leads to a larger sheath field and thus proton beams with a larger cutoff energy and smoother energy spectrum.These results may be useful in achieving high-flux quasi-monoenergetic proton beams by properly designing the hydrocarbon target.
文摘Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separation.Therefore,investigating highly effective COF-based photocatalysts is crucial.For the first time,conjugated COF/perylene diimide urea polymer(PUP)all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF(denoted as TATF-COF)with PUP.The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h^(-1) g^(-1) for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts,resulting in an apparent quantum efficiency of up to 19.7%at 420 nm.The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H_(2) evolution.Experiments and theoretical studies reveal plausible H_(2) evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation.This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.
基金supported by the National Natural Science Foundation of China(20837001 and 21077018)the Program for Changjiang Scholars and Innovative Research Team in University(IRT0813)~~
基金supported by the National Basic Research Program of China (2009CB623604 and 2009CB930604)National Natural Science Foundation of China (U0634003 and 60937001)
文摘A charge carrier mobility of polymer films with the time-of-flight(TOF) technique using a fullerene layer was measured and the TOF photocurrent waveform can be remarkably improved.The 80-nm-thick fullerene layer is functioned as a charge-separation layer(CSL) which was placed between ITO electrode and the polymer layer of MEH-PPV(poly[2-methoxy-5-(2'-ethylhexyloxy) 1,4-phenylenevinylene]).In the CSL,the photo-generated holes and electrons can be efficiently separated,resulting in an enhanced current signal and great improvement of TOF waveform.The sample structure with fullerene layer exhibits a great advantage to measure the hole mobilities of polymers with low energy band gap.
文摘本文将雷暴云的起电、放电物理过程引入中尺度的WRF(Weather Research and Forecasting)模式,并对超级单体和飑线过程进行了模拟研究。起电过程在Milbrandt双参数微物理方案中写入,包含霰、雹与冰晶、雪之间的非感应起电机制,以及霰、雹与云滴之间的感应起电机制。放电参数化方案只考虑了闪电的整体效应。对一次超级单体的模拟结果表明,电荷结构呈现正、负、正的三极性结构,主正电荷区在-40℃到-60℃之间,主负电荷区在-10℃到-30℃之间,下部正电荷区在零度层附近,总电荷浓度最大值接近2nC/m3。这种电荷结构的垂直分布同以往在强对流天气系统中观测到的典型电荷结构一致。对飑线过程的模拟结果表明,部分单体电荷结构呈现出反的偶极性且飑线中最大电荷浓度小于超级单体。在飑线成熟阶段,模拟得到的闪电分布与观测的地闪活动在分布型上相似。
基金the Australian Research Council for the financial support through its DP and FF programsthe Australian Government for the financial support through the Australian Government Research Training Program ScholarshipThe financial support from National Science Foundation of China(No.513228201)
文摘Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.
基金financially supported by the National Key Research and Development Program of China(2017YFA0402800)the National Natural Science Foundation of China(grant nos.51772285,21473170)the Fundamental Research Funds for the Central Universities
文摘Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolution and benzaldehyde production by dehydrogenation of benzyl alcohol over Nidecorated Zn_(0.5)Cd_(0.5)S solid solution under visible light. The photocatalytic system shows an excellent hydrogen production rate of 666.3 μmol h^(-1) with high stability. The optimal apparent quantum yield of52.5% is obtained at 420 nm. This noble-metal-free photocatalytic system displays much higher activity than pure Zn_(0.5)Cd_(0.5)S and Pt-loaded Zn_(0.5)Cd_(0.5)S solid solution. Further studies reveal that the metallic Ni nanocrystals play an important role in accelerating the separation of photogenerated charge carriers and the subsequent cleavage of α-C–H bond during dehydrogenation of benzyl alcohol.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Nos. 21431003 and 21521091） and China Ministry of Science and Technology （No. 2016YFA0202801）. We also thank Dr. Lina Zhang and Ms. Xiaohua Gu for their kind help with the TEM measurements.
文摘Developing low-cost and high-efficiency photocatalysts for hydrogen production from solar water splitting is intriguing but challenging. In this study, unique one-dimensional （1D） multi-node MoS2/CdS hetero-nanowires （NWs） for efficient visible-light photocatalytic H2 evolution are synthesized via a facile hydrothermal method. Flower-like sheaths are assembled from numerous_ defect-rich O-incorporated {0001} MoS2 facet surrounded CdS NW stems are ultrathin nanosheets （NSs）, and {1120}- grown preferentially along the c-axis. Interestingly, the defects in the MoS2 NSs provide additional active S atoms on the exposed edge sites, and the incorporation of O reduces the energy barrier for H2 evolution and increases the electric conductivity of the MoS2 NSs. Moreover, the recombination of photoinduced charge carriers is significantly inhibited by the heterojunction formed between the MoS2 NSs and CdS NWs. Therefore, in the absence of noble metals as co-catalysts, the 1D MoS2 NS/CdS NW hybrids exhibit an excellent H2-generation rate of 10.85 mmol·g^-1·h^-1 and a quantum yield of 22.0% at ,λ = 475 nm, which is far better than those of Pt/CdS NWs, pure MoS2 NSs, and CdS NWs as well as their physical mixtures. Our results contribute to the rational construction of highly reactive nanostructures for various catalytic applications.
基金financial supports from the National Natural Science Foundation of China(Nos.51908485 and 51608468)the China Postdoctoral Science Foundation(No.2019T120194)the University Science and Technology Program Project of Hebei Provincial Department of Education(No.QN2018258)。
文摘Constructing a Z-scheme is a significant approach to improve the separation of photogene rated carriers for effective organic pollutant degradation.Herein,a BiVO4/ZnIn2S4(BZ) Z-scheme composite was successfully synthesized,and applied to photodegrade methyl orange(MO) irradiated by a LED lamp.Anchoring the BiVO4 on the ZnIn2S4 nanoparticles promoted the separation of photogenerated electronholes and broadened the light response range.The detailed characterizations,including surface morphology,elements valence state,and photocurrent performance,demonstrated that the enhanced separation of photogenerated carriers was the pivotal reason for the enhanced photocatalysis reaction.Benefiting from the excellent photocatalytic characteristics,the 5% mass ratio of BZ composite presented the highest MO degradation rate of 0.00997 min^-1,which was 1.9 and 10.3 times greater than the virgin ZnIn2S4 and BiVO4,respectively.Furthermore,the BZ hybrid materials indicated a well photo-stability in the four recycling tests.
基金Supported by the National Natural Science Foundation of China(41205001 and 41030960)National(Key)Basic Research and Development(973)Program of China(2014CB441406)+1 种基金Basic Research Funds of CAMS(2012Y005 and 2013Z006)LASW State Key Laboratory Special Fund
文摘A three-dimensional（3D） charging-discharging cloud resolution model was used to investigate the impact of the vertical velocity field on the charging processes and the formation of charge structure in a strong thunderstorm. The distribution and evolution of ice particle content and charges on ice particles were analyzed in different vertical velocity fields. The results show that the ice particles in the vertical velocity range from 1 to 5 m s-1obtained the most charge through charging processes during the lifetime of the thunderstorm. The magnitude of the charges could reach 1014 n C. Before the beginning of lightning activity,the charges produced in updraft region 2（updraft speed 13 m s-1） and updraft region 1（updraft speed between 5 and 13 m s-1） were relatively significant. The magnitudes of charge reached 1013 n C, which clearly impacted upon the early lightning activity. The vertical velocity conditions in the quasi-steady region（updraft speed between -1 and 1 m s-1） were the most conducive for charge separation on ice particles on different scales. Accordingly, a net charge structure always appeared in the quasi-steady and adjacent regions. Based on the results, a conceptual model of ice particle charging, charge separation, and charge structure formation in the flow field was constructed. The model helps to explain observations of the＂lightning hole＂ phenomenon.
