Novel WO3/g-C3N4/Ni（OH）x hybrids have been successfully synthesized by a two-step strategy of high temperature calcination and in situ photodeposition.Their photocatalytic performance was investigated using TEOA as ...Novel WO3/g-C3N4/Ni（OH）x hybrids have been successfully synthesized by a two-step strategy of high temperature calcination and in situ photodeposition.Their photocatalytic performance was investigated using TEOA as a hole scavenger under visible light irradiation.The loading of WO3 and Ni（OH）x cocatalysts boosted the photocatalytic H2 evolution efficiency of g-C3N4.WO3/g-C3N4/Ni（OH）x with 20 wt%defective WO3 and 4.8 wt%Ni（OH）x showed the highest hydrogen production rate of 576 μmol/（g·h）,which was 5.7,10.8 and 230 times higher than those of g-C3N4/4.8 wt%Ni（OH）x,20 wt%WO3/C3N4 and g-C3N4 photocatalysts,respectively.The remarkably enhanced H2 evolution performance was ascribed to the combination effects of the Z-scheme heterojunction（WO3/g-C3N4） and loaded cocatalysts（Ni（OH）x）,which effectively inhibited the recombination of the photoexcited electron-hole pairs of g-C3N4 and improved both H2 evolution and TEOA oxidation kinetics.The electron spin resonance spectra of ·O2^- and ·OH radicals provided evidence for the Z-scheme charge separation mechanism.The loading of easily available Ni（OH）x cocatalysts on the Z-scheme WO3/g-C3N4 nanocomposites provided insights into constructing a robust multiple-heterojunction material for photocatalytic applications.展开更多
Hole/electron separation and charge transfer are the key processes for enhancing the visible-light photocatalysis performance of heterogeneous photocatalytic systems.To better utilize and understand these effects,bina...Hole/electron separation and charge transfer are the key processes for enhancing the visible-light photocatalysis performance of heterogeneous photocatalytic systems.To better utilize and understand these effects,binary Ag3PO4/Ag2MoO4 hybrid materials were fabricated by a facile solution-phase reaction and characterized systematically by X-ray diffraction（XRD）,energy-dispersive spectroscopy,Fourier transform infrared spectroscopy,Raman spectroscopy,field-emission scanning electron microscopy and ultraviolet-visible diffuse-reflectance spectroscopy.Under visible-light illumination,a heterogeneous Ag3PO4/Ag/Ag2MoO4 photocatalyst was constructed and demonstrated enhanced photocatalytic activity and photostability compared with pristine Ag3PO4toward the remediation of the organic dye rhodamine B.The Ag3PO4/Ag2MoO4 hybrid catalyst with8%mole fraction of Ag2MoO4 exhibited the highest photocatalytic activity toward the removal of typical dye molecules,including methyl orange,methylene blue and phenol aqueous solution.Moreover,the mechanism of the photocatalytic enhancement was investigated via hole- and radical-trapping experiments,photocurrent measurements,electrochemical impedance spectroscopy and XRD measurements.The XRD analysis revealed that metallic Ag nanoparticles formed initially on the surface of the Ag3PO4/Ag2MoO4 composites under visible-light illumination,leading to the generation of a Ag3PO4/Ag/Ag2MoO4 Z-scheme tandem photocatalytic system.The enhanced photocatalytic activity and stability were attributed to the formation of the Ag3PO4/Ag/Ag2MoO4Z-scheme heterojunction and surface plasmon resonance of photo-reduced Ag nanoparticles on the surface.Finally,a plasmonic Z-scheme photocatalytic mechanism was proposed.This work may provide new insights into the design and preparation of advanced visible-light photocatalytic materials and facilitate their practical application in environmental issues.展开更多
Constructing Z-scheme heterojunction to improve the separation efficiency of photogenerated carriers of photocatalysts has gained extensive attention.In this work,we fabricated a novel Z-scheme MoO3/Bi2O4 heterojuncti...Constructing Z-scheme heterojunction to improve the separation efficiency of photogenerated carriers of photocatalysts has gained extensive attention.In this work,we fabricated a novel Z-scheme MoO3/Bi2O4 heterojunction photocatalyst by a hydrothermal method.XPS analysis results indicated that strong interaction between MoO3 and Bi2O4 is generated,which contributes to charge transfer and separation of the photogenerated carriers.This was confirmed by photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)tests.The photocatalytic performance of the as-synthesized photocatalysts was evaluated by degrading rhodamine B(RhB)in aqueous solution under visible light irradiation,showing that 15%MoO3/Bi2O4(15-MB)composite exhibited the highest photocatalytic activity,which is 2 times higher than that of Bi2O4.Besides,the heterojunction photocatalyst can keep good photocatalytic activity and stability after five recycles.Trapping experiments demonstrated that the dominant active radicals in photocatalytic reactions are superoxide radical( O2-)and holes(h+),indicating that the 15-MB composite is a Z-scheme photocatalyst.Finally,the mechanism of the Z-scheme MoO3/Bi2O4 composite for photo-degrading RhB in aqueous solution is proposed.This work provides a promising strategy for designing Bi-based Z-scheme heterojunction photocatalysts for highly efficient removal of environmental pollutants.展开更多
The surface plasmonic resonance(SPR)effect of Bi can effectively improve the light absorption abilities and photogenerated charge carrier separation rate.In this study,a novel ternary heterojunction of g-C3N4/Bi2MoO6/...The surface plasmonic resonance(SPR)effect of Bi can effectively improve the light absorption abilities and photogenerated charge carrier separation rate.In this study,a novel ternary heterojunction of g-C3N4/Bi2MoO6/Bi(CN/BMO/Bi)hollow microsphere was successfully fabricated through solvothermal and in situ reduction methods.The results revealed that the optimal ternary 0.4 CN/BMO/9 Bi photocatalyst exhibited the highest photocatalytic efficiency toward rhodamine B(RhB)degradation with nine times that of pure BMO.The DRS and valence band of the X-ray photoelectron spectroscopy spectrum demonstrate that the band structure of 0.4 CN/BMO/9 Bi is a z-scheme structure.Quenching experiments also provided solid evidence that the·O^2-(at-0.33 eV)is the main species during dye degradation,and the conduction band of g-C3N4 is only the reaction site,demonstrating that the transfer of photogenerated charge carriers of g-C3N4/Bi2 MoO 6/Bi is through an indirect z-scheme structure.Thus,the enhanced photocatalytic performance was mainly ascribed to the synergetic effect of heterojunction structures between g-C3N4 and Bi2MoO6 and the SPR effect of Bi doping,resulting in better optical absorption ability and a lower combination rate of photogenerated charge carriers.The findings in this work provide insight into the synergism of heterostructures and the SPR absorption ability in wastewater treatment.展开更多
A simple calcination method was employed to prepare a Z-scheme N-doped K4Nb6O17/g-C3N4(KCN)heterojunction photocatalyst,in which the electronic structure of K4Nb6O17 was regulated by N-doping,and g-C3N4 was formed bot...A simple calcination method was employed to prepare a Z-scheme N-doped K4Nb6O17/g-C3N4(KCN)heterojunction photocatalyst,in which the electronic structure of K4Nb6O17 was regulated by N-doping,and g-C3N4 was formed both on the surface and within the interlayer spaces of K4Nb6O17.The KCN composite showed profoundly improved photocatalytic activity for both H2 generation and RhB degradation compared to its counterparts.This improved performance was attributed to the synergistic effects of N-doping,which broadened its light harvesting ability,and heterojunction formation,which increased the charge separation rate.The relatively low BET specific surface area of the KCN composite had little effect on its photocatalytic activity.Based on ESR spectroscopy studies,•O2^−,•OH,and h^+are the main active species in the photocatalytic degradation of RhB.Thus,it is reasonable to propose a Z-scheme photocatalytic mechanism over the KCN composite,which exhibits the dual advantages of efficient charge separation and high redox ability.Our work provides a simple approach for constructing large-scale Z-scheme heterojunction photocatalysts with high photocatalytic performance.展开更多
To increase the number of active sites and defects in TiO2 and promote rapid and efficient transfer of photogenerated charges, a g-C3N4@C-TiO2 composite photocatalyst was prepared via in situ deposition of g-C3N4 on a...To increase the number of active sites and defects in TiO2 and promote rapid and efficient transfer of photogenerated charges, a g-C3N4@C-TiO2 composite photocatalyst was prepared via in situ deposition of g-C3N4 on a carbon-doped anatase TiO2 surface. The effects of carbon doping state and surface modification of g-C3N4 on the performance of g-C3N4@C-TiO2 composite photocatalysts were studied by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse-reflectance spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance. With increasing carbon doping content, the carbon doping state in TiO2 gradually changed from gap to substitution doping. Although the number of oxygen vacancies gradually increased, the degradation efficiency of g-C3N4@C-TiO2 for RhB (phenol) initially increased and subsequently decreased with increasing carbon content. The g-C3N4@10C-TiO2 sample exhibited the highest apparent reaction rate constant of 0.036 min儃1 (0.039 min儃1) for RhB (phenol) degradation, which was 150 (139), 6.4 (6.8), 2.3 (3), and 1.7 (2.1) times higher than that of pure TiO2, 10C-TiO2, g-C3N4, and g-C3N4@TiO2, respectively. g-C3N4 was grown in situ on the surface of C-TiO2 by surface carbon hybridization and bonding. The resultant novel g-C3N4@C-TiO2 photocatalyst exhibited direct Z-scheme heterojunctions with non-local impurity levels. The high photocatalytic activity can be attributed to the synergistic effects of the improved visible light response ability, higher photogenerated electron transfer efficiency, and redox ability arising from Z-type heterojunctions.展开更多
Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical(PEC)water splitting.Among the many obstacles facing a Z-scheme photocatalytic system,the analysis methods of inte...Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical(PEC)water splitting.Among the many obstacles facing a Z-scheme photocatalytic system,the analysis methods of interfacial Z-scheme charge transfer still remain a significant challenge.Hence,in this study,CdS/Ti-Fe_(2)O_(3)heterojunction photoanodes are elaborately designed to explore the charge-transfer behavior in PEC water splitting.In this study,photophysical measurements,including the Kelvin probe measurement,surface photovoltage spectroscopy(SPV),and transient photovoltage spectroscopy(TPV),are used to monitor the migration behavior of photogenerated charges at the interface electric field of CdS/Ti-Fe_(2)O_(3)Z-scheme heterojunction photoanodes.The Kelvin probe and SPV measurements demonstrate that CdS/Ti-Fe_(2)O_(3)interfacial driving force favors the rapid transfer of photoexcited electrons to CdS.The double-beam strategy based on TPV indicates that more electrons of Ti-Fe_(2)O_(3)are combined with the holes of CdS owing to the intensive interface electric field.The results of these measurements successfully prove the Z-scheme migration mechanism of CdS/Ti-Fe_(2)O_(3)photoanodes.Benefiting from the desirable charge transfer at the interface electric field,CdS/Ti-Fe_(2)O_(3)photoanodes exhibit superior photocatalytic oxygen evolution reaction performance compared with that of pure Ti-Fe_(2)O_(3).The photocurrent density of the 25CdS/Ti-Fe_(2)O_(3)photoanode reaches 1.94 mA/cm^(2) at 1.23 V versus reversible hydrogen electrode without excess cocatalyst,and it is two times higher than that of pure Ti-Fe_(2)O_(3)photoanode.Therefore,an outstanding strategy is provided in this study to prove the Z-scheme charge-transfer mechanism of photocatalytic systems in PEC water splitting.展开更多
TiO2 nanoparticles were prepared using the hydrothermal method and modified with CgN to syn-thesize a Type-Ⅱheterojunction semiconductor photocatalyst,TiO2-C;Na.In addition,a carbon layerwas coated onto the TiO2 nano...TiO2 nanoparticles were prepared using the hydrothermal method and modified with CgN to syn-thesize a Type-Ⅱheterojunction semiconductor photocatalyst,TiO2-C;Na.In addition,a carbon layerwas coated onto the TiO2 nanoparticles and the obtained material was uniformly covered on thesurface of CaNa to form an all-solid-state Z-scheme semiconductor photocatalyst,TiO2-C-C3N4,Through characterization by XRD,XPS,SEM,TEM,BET,photoelectrochemical experiments,UV-visible diffuse reflection,and PL spectroscopy,the charge transfer mechanism and band gappositions for the composite photocatalysts were analyzed.The Type-Ⅱand all-solid-state Z-schemeheterojunction structures were compared.By combining microscopic internal mechanisms withmacroscopic experimental phenomena,the relationship between performance and structure wasverified.Experimental methods were used to explore the adaptation degree of different photocata-lytic mechanisms using the same degradation system.This study highlights effective photocatalystdesign to meet the requirements for specific degradation conditions.展开更多
It is still challenging for exploring high-active photocatalysts to efficiently remove levofloxacin(LFX)by activating peroxymonosulfate(PMS).Herein,we constructed a novel Z scheme ZnFe_(2)O_(4)/g-C_(3)N_(4)/CQDs(ZCC)h...It is still challenging for exploring high-active photocatalysts to efficiently remove levofloxacin(LFX)by activating peroxymonosulfate(PMS).Herein,we constructed a novel Z scheme ZnFe_(2)O_(4)/g-C_(3)N_(4)/CQDs(ZCC)heterojunction by anchoring ZnFe_(2)O_(4)on tubular-like g-C_(3)N_(4)induced by CQDs(denoted as CNC)using microwave-assisted thermal methods.The ZCC exhibits the highest photocatalytic activity in activating PMS for LFX degradation,endowing a removal rate~95.3%,which is 4.8 and 7.3 times that of pure ZnFe_(2)O_(4)(19.8%)and g-C_(3)N_(4)(13.1%),separately.The enhanced photocatalytic activity of ZCC can be attributed to the distinctive morphology of CNC,enhanced light response,increased specific surface area and abundant pore structure.Besides,the formed Z scheme heterojunction and CQDs acting as a transmission bridge of the photogenerated charges(e−and h+)can accelerate transfer and inhibit recombination of e−and h+.Radical capture experiments and electron spin resonance(ESR)measurements revealed that SO4•-and O2•-play a predominant role in degradation process of LFX.Liquid chromatography-mass spectrometry(LC-MS)was applied to identify intermediates and propose feasible degradation pathways of LFX.In conclusion,this study presents a promising strategy for regulating the photocatalytic activity of g-C_(3)N_(4)by simultaneously integrating CQDs induction and Z scheme heterojunction construction.展开更多
Simultaneously utilizing photogenerated electrons and holes to convert renewable biomass and its derivatives into corresponding value‐added products and hydrogen(H_(2))is a promising strategy to deal with the energy ...Simultaneously utilizing photogenerated electrons and holes to convert renewable biomass and its derivatives into corresponding value‐added products and hydrogen(H_(2))is a promising strategy to deal with the energy and environmental crisis.Herein,we report a facile hydrothermal method to construct a direct Z‐scheme CdS/WO_(3) binary composite for photocatalytic coupling redox reaction,simultaneously producing H_(2) and selectively converting aromatic alcohols into aromatic aldehydes in one pot.Compared with bare CdS and WO_(3),the CdS/WO_(3) binary composite exhibits significantly enhanced performance for this photocatalytic coupled redox reaction,which is ascribed to the ex‐tended light harvesting range,efficient charge carrier separation rate and optimized redox capabil‐ity of CdS/WO_(3) composite.Furthermore,the feasibility of converting various aromatic alcohols to corresponding aldehydes coupled with H_(2) evolution on the CdS/WO_(3) photocatalyst is proved and a reasonable reaction mechanism is proposed.It is hoped that this work can provide a new insight into the construction of direct Z‐scheme photocatalysts to effectively utilize the photogenerated electrons and holes for photocatalytic coupled redox reaction.展开更多
To alleviate the growing serious ecological threats brought by carbon-based fuels,it is a promising approach to construct a Z-scheme heterojunction via simulating the photosynthetic mechanism for solar-driven CO_(2)re...To alleviate the growing serious ecological threats brought by carbon-based fuels,it is a promising approach to construct a Z-scheme heterojunction via simulating the photosynthetic mechanism for solar-driven CO_(2)reduction into high value-added chemical fuels.Herein,we design and prepare a Z-scheme composite photocatalyst based on coupling metalloporphyrin-like Co_(x)-CN with Keggin-type POMs(PMo_(10)V_(2)O_(40)^(5-))by electrostatic interactions.By virtue of the redox property and charge transfer mechanism similar to chlorophyll P700 and P680 in green plants,the composite heterojunction exhibits broadspectrum absorption and strong CO_(2)absorption capacity,as well as the inhibition of the recombination of photo-introduced carriers.Under visible light irradiation,the optimized 0.05PMo_(10)V_(2)/Co_(1)-CN heterojunction shows the highest CO yield of 101.38μmol·g^(-1)·h^(-1),which is increased by about 250 and 9 times compared with those of CN and Co_(1)-CN,respectively,and concomitantly inhibits competitive H_(2) generation.This work provides a promising strategy to develop high-efficiency and low-cost Z-scheme photocatalysts for CO_(2)conversion.展开更多
基金supported by the National Natural Science Foundation of China (51672089)the Industry and Research Collaborative Innovation Major Projects of Guangzhou (201508020098)+1 种基金the State Key Laboratory of Advanced Technology for Material Synthesis and Processing (Wuhan University of Technology) (2015-KF-7)the Hunan Key Laboratory of Applied Environmental Photocatalysis (Changsha University) (CCSU-XT-04)~~
文摘Novel WO3/g-C3N4/Ni（OH）x hybrids have been successfully synthesized by a two-step strategy of high temperature calcination and in situ photodeposition.Their photocatalytic performance was investigated using TEOA as a hole scavenger under visible light irradiation.The loading of WO3 and Ni（OH）x cocatalysts boosted the photocatalytic H2 evolution efficiency of g-C3N4.WO3/g-C3N4/Ni（OH）x with 20 wt%defective WO3 and 4.8 wt%Ni（OH）x showed the highest hydrogen production rate of 576 μmol/（g·h）,which was 5.7,10.8 and 230 times higher than those of g-C3N4/4.8 wt%Ni（OH）x,20 wt%WO3/C3N4 and g-C3N4 photocatalysts,respectively.The remarkably enhanced H2 evolution performance was ascribed to the combination effects of the Z-scheme heterojunction（WO3/g-C3N4） and loaded cocatalysts（Ni（OH）x）,which effectively inhibited the recombination of the photoexcited electron-hole pairs of g-C3N4 and improved both H2 evolution and TEOA oxidation kinetics.The electron spin resonance spectra of ·O2^- and ·OH radicals provided evidence for the Z-scheme charge separation mechanism.The loading of easily available Ni（OH）x cocatalysts on the Z-scheme WO3/g-C3N4 nanocomposites provided insights into constructing a robust multiple-heterojunction material for photocatalytic applications.
基金supported by the National Natural Science Foundation of China (51672113, 51302112)the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology, 2016-KF-10)~~
文摘Hole/electron separation and charge transfer are the key processes for enhancing the visible-light photocatalysis performance of heterogeneous photocatalytic systems.To better utilize and understand these effects,binary Ag3PO4/Ag2MoO4 hybrid materials were fabricated by a facile solution-phase reaction and characterized systematically by X-ray diffraction（XRD）,energy-dispersive spectroscopy,Fourier transform infrared spectroscopy,Raman spectroscopy,field-emission scanning electron microscopy and ultraviolet-visible diffuse-reflectance spectroscopy.Under visible-light illumination,a heterogeneous Ag3PO4/Ag/Ag2MoO4 photocatalyst was constructed and demonstrated enhanced photocatalytic activity and photostability compared with pristine Ag3PO4toward the remediation of the organic dye rhodamine B.The Ag3PO4/Ag2MoO4 hybrid catalyst with8%mole fraction of Ag2MoO4 exhibited the highest photocatalytic activity toward the removal of typical dye molecules,including methyl orange,methylene blue and phenol aqueous solution.Moreover,the mechanism of the photocatalytic enhancement was investigated via hole- and radical-trapping experiments,photocurrent measurements,electrochemical impedance spectroscopy and XRD measurements.The XRD analysis revealed that metallic Ag nanoparticles formed initially on the surface of the Ag3PO4/Ag2MoO4 composites under visible-light illumination,leading to the generation of a Ag3PO4/Ag/Ag2MoO4 Z-scheme tandem photocatalytic system.The enhanced photocatalytic activity and stability were attributed to the formation of the Ag3PO4/Ag/Ag2MoO4Z-scheme heterojunction and surface plasmon resonance of photo-reduced Ag nanoparticles on the surface.Finally,a plasmonic Z-scheme photocatalytic mechanism was proposed.This work may provide new insights into the design and preparation of advanced visible-light photocatalytic materials and facilitate their practical application in environmental issues.
基金supported by the Natural Science Foundation of Hubei Province(2016CFA078)the National Natural Science Foundation of China(51472194)~~
文摘Constructing Z-scheme heterojunction to improve the separation efficiency of photogenerated carriers of photocatalysts has gained extensive attention.In this work,we fabricated a novel Z-scheme MoO3/Bi2O4 heterojunction photocatalyst by a hydrothermal method.XPS analysis results indicated that strong interaction between MoO3 and Bi2O4 is generated,which contributes to charge transfer and separation of the photogenerated carriers.This was confirmed by photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)tests.The photocatalytic performance of the as-synthesized photocatalysts was evaluated by degrading rhodamine B(RhB)in aqueous solution under visible light irradiation,showing that 15%MoO3/Bi2O4(15-MB)composite exhibited the highest photocatalytic activity,which is 2 times higher than that of Bi2O4.Besides,the heterojunction photocatalyst can keep good photocatalytic activity and stability after five recycles.Trapping experiments demonstrated that the dominant active radicals in photocatalytic reactions are superoxide radical( O2-)and holes(h+),indicating that the 15-MB composite is a Z-scheme photocatalyst.Finally,the mechanism of the Z-scheme MoO3/Bi2O4 composite for photo-degrading RhB in aqueous solution is proposed.This work provides a promising strategy for designing Bi-based Z-scheme heterojunction photocatalysts for highly efficient removal of environmental pollutants.
基金financially supported by the Science Foundation of China University of Petroleum,Beijing(2462017YJRC048,2462018BJC005)the National Natural Science Foundation of China(51802351)~~
文摘The surface plasmonic resonance(SPR)effect of Bi can effectively improve the light absorption abilities and photogenerated charge carrier separation rate.In this study,a novel ternary heterojunction of g-C3N4/Bi2MoO6/Bi(CN/BMO/Bi)hollow microsphere was successfully fabricated through solvothermal and in situ reduction methods.The results revealed that the optimal ternary 0.4 CN/BMO/9 Bi photocatalyst exhibited the highest photocatalytic efficiency toward rhodamine B(RhB)degradation with nine times that of pure BMO.The DRS and valence band of the X-ray photoelectron spectroscopy spectrum demonstrate that the band structure of 0.4 CN/BMO/9 Bi is a z-scheme structure.Quenching experiments also provided solid evidence that the·O^2-(at-0.33 eV)is the main species during dye degradation,and the conduction band of g-C3N4 is only the reaction site,demonstrating that the transfer of photogenerated charge carriers of g-C3N4/Bi2 MoO 6/Bi is through an indirect z-scheme structure.Thus,the enhanced photocatalytic performance was mainly ascribed to the synergetic effect of heterojunction structures between g-C3N4 and Bi2MoO6 and the SPR effect of Bi doping,resulting in better optical absorption ability and a lower combination rate of photogenerated charge carriers.The findings in this work provide insight into the synergism of heterostructures and the SPR absorption ability in wastewater treatment.
文摘A simple calcination method was employed to prepare a Z-scheme N-doped K4Nb6O17/g-C3N4(KCN)heterojunction photocatalyst,in which the electronic structure of K4Nb6O17 was regulated by N-doping,and g-C3N4 was formed both on the surface and within the interlayer spaces of K4Nb6O17.The KCN composite showed profoundly improved photocatalytic activity for both H2 generation and RhB degradation compared to its counterparts.This improved performance was attributed to the synergistic effects of N-doping,which broadened its light harvesting ability,and heterojunction formation,which increased the charge separation rate.The relatively low BET specific surface area of the KCN composite had little effect on its photocatalytic activity.Based on ESR spectroscopy studies,•O2^−,•OH,and h^+are the main active species in the photocatalytic degradation of RhB.Thus,it is reasonable to propose a Z-scheme photocatalytic mechanism over the KCN composite,which exhibits the dual advantages of efficient charge separation and high redox ability.Our work provides a simple approach for constructing large-scale Z-scheme heterojunction photocatalysts with high photocatalytic performance.
基金supported by the National Natural Science Foundation of China(51772140)the Natural Science Foundation of Jiangxi Province,China(20161BAB206111,20171ACB21033)the Scientific Research Foundation of Jiangxi Provincial Education Department,China(GJJ170578)~~
文摘To increase the number of active sites and defects in TiO2 and promote rapid and efficient transfer of photogenerated charges, a g-C3N4@C-TiO2 composite photocatalyst was prepared via in situ deposition of g-C3N4 on a carbon-doped anatase TiO2 surface. The effects of carbon doping state and surface modification of g-C3N4 on the performance of g-C3N4@C-TiO2 composite photocatalysts were studied by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse-reflectance spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance. With increasing carbon doping content, the carbon doping state in TiO2 gradually changed from gap to substitution doping. Although the number of oxygen vacancies gradually increased, the degradation efficiency of g-C3N4@C-TiO2 for RhB (phenol) initially increased and subsequently decreased with increasing carbon content. The g-C3N4@10C-TiO2 sample exhibited the highest apparent reaction rate constant of 0.036 min儃1 (0.039 min儃1) for RhB (phenol) degradation, which was 150 (139), 6.4 (6.8), 2.3 (3), and 1.7 (2.1) times higher than that of pure TiO2, 10C-TiO2, g-C3N4, and g-C3N4@TiO2, respectively. g-C3N4 was grown in situ on the surface of C-TiO2 by surface carbon hybridization and bonding. The resultant novel g-C3N4@C-TiO2 photocatalyst exhibited direct Z-scheme heterojunctions with non-local impurity levels. The high photocatalytic activity can be attributed to the synergistic effects of the improved visible light response ability, higher photogenerated electron transfer efficiency, and redox ability arising from Z-type heterojunctions.
文摘Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical(PEC)water splitting.Among the many obstacles facing a Z-scheme photocatalytic system,the analysis methods of interfacial Z-scheme charge transfer still remain a significant challenge.Hence,in this study,CdS/Ti-Fe_(2)O_(3)heterojunction photoanodes are elaborately designed to explore the charge-transfer behavior in PEC water splitting.In this study,photophysical measurements,including the Kelvin probe measurement,surface photovoltage spectroscopy(SPV),and transient photovoltage spectroscopy(TPV),are used to monitor the migration behavior of photogenerated charges at the interface electric field of CdS/Ti-Fe_(2)O_(3)Z-scheme heterojunction photoanodes.The Kelvin probe and SPV measurements demonstrate that CdS/Ti-Fe_(2)O_(3)interfacial driving force favors the rapid transfer of photoexcited electrons to CdS.The double-beam strategy based on TPV indicates that more electrons of Ti-Fe_(2)O_(3)are combined with the holes of CdS owing to the intensive interface electric field.The results of these measurements successfully prove the Z-scheme migration mechanism of CdS/Ti-Fe_(2)O_(3)photoanodes.Benefiting from the desirable charge transfer at the interface electric field,CdS/Ti-Fe_(2)O_(3)photoanodes exhibit superior photocatalytic oxygen evolution reaction performance compared with that of pure Ti-Fe_(2)O_(3).The photocurrent density of the 25CdS/Ti-Fe_(2)O_(3)photoanode reaches 1.94 mA/cm^(2) at 1.23 V versus reversible hydrogen electrode without excess cocatalyst,and it is two times higher than that of pure Ti-Fe_(2)O_(3)photoanode.Therefore,an outstanding strategy is provided in this study to prove the Z-scheme charge-transfer mechanism of photocatalytic systems in PEC water splitting.
文摘TiO2 nanoparticles were prepared using the hydrothermal method and modified with CgN to syn-thesize a Type-Ⅱheterojunction semiconductor photocatalyst,TiO2-C;Na.In addition,a carbon layerwas coated onto the TiO2 nanoparticles and the obtained material was uniformly covered on thesurface of CaNa to form an all-solid-state Z-scheme semiconductor photocatalyst,TiO2-C-C3N4,Through characterization by XRD,XPS,SEM,TEM,BET,photoelectrochemical experiments,UV-visible diffuse reflection,and PL spectroscopy,the charge transfer mechanism and band gappositions for the composite photocatalysts were analyzed.The Type-Ⅱand all-solid-state Z-schemeheterojunction structures were compared.By combining microscopic internal mechanisms withmacroscopic experimental phenomena,the relationship between performance and structure wasverified.Experimental methods were used to explore the adaptation degree of different photocata-lytic mechanisms using the same degradation system.This study highlights effective photocatalystdesign to meet the requirements for specific degradation conditions.
基金Project(32272823) supported by the National Natural Science Foundation of ChinaProject(145309315) supported by the Research Foundation of Education Bureau of Heilongjiang Province of ChinaProject(YSTSXK202309) supported by the Plant Food Processing Technology Advantages Characteristic Discipline “Science and Technology Research” Special Project in Heilongjiang Province,China。
文摘It is still challenging for exploring high-active photocatalysts to efficiently remove levofloxacin(LFX)by activating peroxymonosulfate(PMS).Herein,we constructed a novel Z scheme ZnFe_(2)O_(4)/g-C_(3)N_(4)/CQDs(ZCC)heterojunction by anchoring ZnFe_(2)O_(4)on tubular-like g-C_(3)N_(4)induced by CQDs(denoted as CNC)using microwave-assisted thermal methods.The ZCC exhibits the highest photocatalytic activity in activating PMS for LFX degradation,endowing a removal rate~95.3%,which is 4.8 and 7.3 times that of pure ZnFe_(2)O_(4)(19.8%)and g-C_(3)N_(4)(13.1%),separately.The enhanced photocatalytic activity of ZCC can be attributed to the distinctive morphology of CNC,enhanced light response,increased specific surface area and abundant pore structure.Besides,the formed Z scheme heterojunction and CQDs acting as a transmission bridge of the photogenerated charges(e−and h+)can accelerate transfer and inhibit recombination of e−and h+.Radical capture experiments and electron spin resonance(ESR)measurements revealed that SO4•-and O2•-play a predominant role in degradation process of LFX.Liquid chromatography-mass spectrometry(LC-MS)was applied to identify intermediates and propose feasible degradation pathways of LFX.In conclusion,this study presents a promising strategy for regulating the photocatalytic activity of g-C_(3)N_(4)by simultaneously integrating CQDs induction and Z scheme heterojunction construction.
文摘Simultaneously utilizing photogenerated electrons and holes to convert renewable biomass and its derivatives into corresponding value‐added products and hydrogen(H_(2))is a promising strategy to deal with the energy and environmental crisis.Herein,we report a facile hydrothermal method to construct a direct Z‐scheme CdS/WO_(3) binary composite for photocatalytic coupling redox reaction,simultaneously producing H_(2) and selectively converting aromatic alcohols into aromatic aldehydes in one pot.Compared with bare CdS and WO_(3),the CdS/WO_(3) binary composite exhibits significantly enhanced performance for this photocatalytic coupled redox reaction,which is ascribed to the ex‐tended light harvesting range,efficient charge carrier separation rate and optimized redox capabil‐ity of CdS/WO_(3) composite.Furthermore,the feasibility of converting various aromatic alcohols to corresponding aldehydes coupled with H_(2) evolution on the CdS/WO_(3) photocatalyst is proved and a reasonable reaction mechanism is proposed.It is hoped that this work can provide a new insight into the construction of direct Z‐scheme photocatalysts to effectively utilize the photogenerated electrons and holes for photocatalytic coupled redox reaction.
基金supported by the National Natural Science Foundation of China(22071020,22171041,22379024,22205034)the Natural Science Foundation of Jilin Province Science and Technology Department(20230508094RC and 20240101178JC)the Fundamental Research Funds for Central Universities(2412022QD012)
文摘To alleviate the growing serious ecological threats brought by carbon-based fuels,it is a promising approach to construct a Z-scheme heterojunction via simulating the photosynthetic mechanism for solar-driven CO_(2)reduction into high value-added chemical fuels.Herein,we design and prepare a Z-scheme composite photocatalyst based on coupling metalloporphyrin-like Co_(x)-CN with Keggin-type POMs(PMo_(10)V_(2)O_(40)^(5-))by electrostatic interactions.By virtue of the redox property and charge transfer mechanism similar to chlorophyll P700 and P680 in green plants,the composite heterojunction exhibits broadspectrum absorption and strong CO_(2)absorption capacity,as well as the inhibition of the recombination of photo-introduced carriers.Under visible light irradiation,the optimized 0.05PMo_(10)V_(2)/Co_(1)-CN heterojunction shows the highest CO yield of 101.38μmol·g^(-1)·h^(-1),which is increased by about 250 and 9 times compared with those of CN and Co_(1)-CN,respectively,and concomitantly inhibits competitive H_(2) generation.This work provides a promising strategy to develop high-efficiency and low-cost Z-scheme photocatalysts for CO_(2)conversion.
