To further improve the charge separation and photocatalytic activities of g-C3N4 and CdMoO4 under visible light irradiation,CdMoO4/g-C3N4 composites were rationally synthesized by a facile precipitation-calcination pr...To further improve the charge separation and photocatalytic activities of g-C3N4 and CdMoO4 under visible light irradiation,CdMoO4/g-C3N4 composites were rationally synthesized by a facile precipitation-calcination procedure.The crystal phases,morphologies,chemical compositions,textural structures,and optical properties of the as-prepared composites were characterized by the corresponding analytical techniques.The photocatalytic activities toward degradation of rhodamine B solution were evaluated under visible light irradiation.The results revealed that integrating CdMoO4 with g-C3N4 could remarkably improve the charge separation and photocatalytic activity,compared with those of pristine g-C3N4 and CdMoO4.This would be because the CdMoO4/g-C3N4 composites could facilitate the transfer and separation of the photoexcited electron-hole pairs,which was confirmed by electrochemical impedance spectroscopy,transient photocurrent responses,and photoluminescence measurements.Moreover,active species trapping experiments demonstrated that holes(h+)and superoxide radicals(?O2?)were the main active species during the photocatalytic reaction.A possible photocatalytic mechanism was proposed on the basis of the energy band structures determined by Mott-Schottky tests.This work would provide further insights into the rational fabrication of composites for organic contaminant removal.展开更多
Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g...Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g ） = 3 Si2 N2O （ s ） ＋ N2 （ g ） . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition ： amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa （Vickers） at 1 600 ℃ .展开更多
A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process ...A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra （EDS） result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction （XRD） results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope （SEM）. As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.展开更多
Constructing step-scheme(S-scheme)heterojunctions has been confirmed as a promising strategy for enhancing the photocatalytic activity of composite materials.In this work,a series of sulfur-doped g-C3N4(SCN)/TiO2 S-sc...Constructing step-scheme(S-scheme)heterojunctions has been confirmed as a promising strategy for enhancing the photocatalytic activity of composite materials.In this work,a series of sulfur-doped g-C3N4(SCN)/TiO2 S-scheme photocatalysts were synthesized using electrospinning and calcination methods.The as-prepared SCN/TiO2 composites showed superior photocatalytic performance than pure TiO2 and SCN in the photocatalytic degradation of Congo Red(CR)aqueous solution.The significant enhancement in photocatalytic activity benefited not only from the 1D well-distributed nanostructure,but also from the S-scheme heterojunction.Furthermore,the XPS analyses and DFT calculations demonstrated that electrons were transferred from SCN to TiO2 across the interface of the SCN/TiO2 composites.The built-in electric field,band edge bending,and Coulomb interaction synergistically facilitated the recombination of relatively useless electrons and holes in hybrid when the interface was irradiated by simulated solar light.Therefore,the remaining electrons and holes with higher reducibility and oxidizability endowed the composite with supreme redox ability.These results were adequately verified by radical trapping experiments,ESR tests,and in situ XPS analyses,suggesting that the electron immigration in the photocatalyst followed the S-scheme heterojunction mechanism.This work can enrich our knowledge of the design and fabrication of novel S-scheme heterojunction photocatalysts and provide a promising strategy for solving environmental pollution in the future.展开更多
Photocatalytic H_(2)production from water splitting is a promising candidate for solving the increasing energy crisis and environmental issues.Herein we report a novel g-C_(3)N_(4)/Ag In_(x)S_(y)S-scheme heterojunctio...Photocatalytic H_(2)production from water splitting is a promising candidate for solving the increasing energy crisis and environmental issues.Herein we report a novel g-C_(3)N_(4)/Ag In_(x)S_(y)S-scheme heterojunction photocatalyst for water splitting into stoichiometric H_(2)and H_(2)O_(2)under visible light.The catalyst was prepared by depositing 3D bimetallic sulfide(Ag In_(x)S_(y))nanotubes onto 2D g-C_(3)N_(4)nanosheets.Owing to the special 3D-on-2D configuration,the photogenerated carriers could be rapidly transferred and effectively separated through the abundant interfacial heterostructures to avoid recombination,and therefore excellent performance for visible light-driven water splitting could be obtained,with a 24-h H_(2)evolution rate up to 237μmol g^(-1)h^(-1).Furthermore,suitable band alignment enables simultaneous H_(2)and H_(2)O_(2)production in a 1:1 stoichiometric ratio.H_(2)and H_(2)O_(2)were evolved on the conduction band of g-C_(3)N_(4)and on the valance band of Ag In_(x)S_(y),respectively.The novel 3D-on-2D configuration for heterojunction construction proposed in this work provided alternative research ideas toward photocatalytic reaction.展开更多
The development of low cost, metal free semiconductor photocatalysts for CO2 reduction to fuels and valuable chemical feedstocks is a practically imperative for reducing anthropogenic CO2 emissions. In this work, blac...The development of low cost, metal free semiconductor photocatalysts for CO2 reduction to fuels and valuable chemical feedstocks is a practically imperative for reducing anthropogenic CO2 emissions. In this work, black phosphorus quantum dots（BPQDs） were successfully dispersed on a graphitic carbon nitride（g-C3N4） support via a simple electrostatic attraction approach, and the activities of BP@g-C3N4 composites were evaluated for photocatalytic CO2 reduction. The BP@g-C3N4 composites displayed improved carrier separation efficiency and higher activities for photocatalytic CO2 reduction to CO（6.54 μmol g^-1h^-1 at the optimum BPQDs loading of 1 wt%） compared with pure g-C3N4（2.65 μmol g^-1h^-1）. This work thus identifies a novel approach towards metal free photocatalysts for CO2 photoreduction.展开更多
将工业偏钛酸浆料和尿素混合均匀后高温煅烧制备g-C3N4/TiO2光催化复合材料,对其结构进行了表征,以NO为目标物、波长430~470 nm的12 W LED灯为光源,用对NO的去除率评价复合材料的气相光催化活性.结果表明,所制样品为氮掺杂Ti O2与g-C3N4...将工业偏钛酸浆料和尿素混合均匀后高温煅烧制备g-C3N4/TiO2光催化复合材料,对其结构进行了表征,以NO为目标物、波长430~470 nm的12 W LED灯为光源,用对NO的去除率评价复合材料的气相光催化活性.结果表明,所制样品为氮掺杂Ti O2与g-C3N4/TiO2的复合物.复合材料的最佳制备条件为尿素与偏钛酸质量比2：1,450℃下煅烧1 h,该条件下样品产率最高,对NO的去除率达48.40%.展开更多
基金supported by the Open Project Program of Hubei Key Laboratory of Animal Nutrition and Feed Science,Wuhan Polytechnic University(No.201808)Hubei Important Project of Technological Innovation(2018ABA094)~~
文摘To further improve the charge separation and photocatalytic activities of g-C3N4 and CdMoO4 under visible light irradiation,CdMoO4/g-C3N4 composites were rationally synthesized by a facile precipitation-calcination procedure.The crystal phases,morphologies,chemical compositions,textural structures,and optical properties of the as-prepared composites were characterized by the corresponding analytical techniques.The photocatalytic activities toward degradation of rhodamine B solution were evaluated under visible light irradiation.The results revealed that integrating CdMoO4 with g-C3N4 could remarkably improve the charge separation and photocatalytic activity,compared with those of pristine g-C3N4 and CdMoO4.This would be because the CdMoO4/g-C3N4 composites could facilitate the transfer and separation of the photoexcited electron-hole pairs,which was confirmed by electrochemical impedance spectroscopy,transient photocurrent responses,and photoluminescence measurements.Moreover,active species trapping experiments demonstrated that holes(h+)and superoxide radicals(?O2?)were the main active species during the photocatalytic reaction.A possible photocatalytic mechanism was proposed on the basis of the energy band structures determined by Mott-Schottky tests.This work would provide further insights into the rational fabrication of composites for organic contaminant removal.
基金Funded by the National Science Foundation of China ( No.50375037)
文摘Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g ） = 3 Si2 N2O （ s ） ＋ N2 （ g ） . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition ： amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa （Vickers） at 1 600 ℃ .
基金This study was financially supported by the Key Foundation of National Science in China (No. 90405015), the National Elitist Youth Foundation of China (No. 50425208the Doctorate Foundation of Northwestern Polytechnical University (CX200505).
文摘A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra （EDS） result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction （XRD） results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope （SEM）. As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.
文摘Constructing step-scheme(S-scheme)heterojunctions has been confirmed as a promising strategy for enhancing the photocatalytic activity of composite materials.In this work,a series of sulfur-doped g-C3N4(SCN)/TiO2 S-scheme photocatalysts were synthesized using electrospinning and calcination methods.The as-prepared SCN/TiO2 composites showed superior photocatalytic performance than pure TiO2 and SCN in the photocatalytic degradation of Congo Red(CR)aqueous solution.The significant enhancement in photocatalytic activity benefited not only from the 1D well-distributed nanostructure,but also from the S-scheme heterojunction.Furthermore,the XPS analyses and DFT calculations demonstrated that electrons were transferred from SCN to TiO2 across the interface of the SCN/TiO2 composites.The built-in electric field,band edge bending,and Coulomb interaction synergistically facilitated the recombination of relatively useless electrons and holes in hybrid when the interface was irradiated by simulated solar light.Therefore,the remaining electrons and holes with higher reducibility and oxidizability endowed the composite with supreme redox ability.These results were adequately verified by radical trapping experiments,ESR tests,and in situ XPS analyses,suggesting that the electron immigration in the photocatalyst followed the S-scheme heterojunction mechanism.This work can enrich our knowledge of the design and fabrication of novel S-scheme heterojunction photocatalysts and provide a promising strategy for solving environmental pollution in the future.
基金financially supported by the National Natural Science Foundation of China(Nos.52362012,42077162,51978323)Natural Science Foundation of Jiangxi Province(No.2022ACB203014)+4 种基金Major Discipline Academic and Technical Leaders Training Program of Jiangxi Province(Nos.20213BCJ22018,20232BCJ22048)Natural Science Project of the Educational Department in Jiangxi Province(No.GJJ2201121)Natural Science Foundation of Nanchang Hangkong University(No.EA202202256)Educational Reform Project of Jiangxi Province(No.JXYJG-2022-135)Nanchang Hangkong University Educational Reform Project(Nos.sz2214,sz2213,JY22017,KCPY1806)。
文摘Photocatalytic H_(2)production from water splitting is a promising candidate for solving the increasing energy crisis and environmental issues.Herein we report a novel g-C_(3)N_(4)/Ag In_(x)S_(y)S-scheme heterojunction photocatalyst for water splitting into stoichiometric H_(2)and H_(2)O_(2)under visible light.The catalyst was prepared by depositing 3D bimetallic sulfide(Ag In_(x)S_(y))nanotubes onto 2D g-C_(3)N_(4)nanosheets.Owing to the special 3D-on-2D configuration,the photogenerated carriers could be rapidly transferred and effectively separated through the abundant interfacial heterostructures to avoid recombination,and therefore excellent performance for visible light-driven water splitting could be obtained,with a 24-h H_(2)evolution rate up to 237μmol g^(-1)h^(-1).Furthermore,suitable band alignment enables simultaneous H_(2)and H_(2)O_(2)production in a 1:1 stoichiometric ratio.H_(2)and H_(2)O_(2)were evolved on the conduction band of g-C_(3)N_(4)and on the valance band of Ag In_(x)S_(y),respectively.The novel 3D-on-2D configuration for heterojunction construction proposed in this work provided alternative research ideas toward photocatalytic reaction.
基金supported by the National Natural Science Foundation of China (51502146, U1404506, 21671113, 51772305, 51572270, and U1662118)the International Partnership Program of Chinese Academy of Sciences (GJHZ1819)+1 种基金the Royal Society-Newton Advanced Fellowship (NA170422)supported by Open Fund (PEBM201702) of Key Laboratory for Photonic and Electric Bandgap Materials, Ministry of Education (Harbin Normal University)
文摘The development of low cost, metal free semiconductor photocatalysts for CO2 reduction to fuels and valuable chemical feedstocks is a practically imperative for reducing anthropogenic CO2 emissions. In this work, black phosphorus quantum dots（BPQDs） were successfully dispersed on a graphitic carbon nitride（g-C3N4） support via a simple electrostatic attraction approach, and the activities of BP@g-C3N4 composites were evaluated for photocatalytic CO2 reduction. The BP@g-C3N4 composites displayed improved carrier separation efficiency and higher activities for photocatalytic CO2 reduction to CO（6.54 μmol g^-1h^-1 at the optimum BPQDs loading of 1 wt%） compared with pure g-C3N4（2.65 μmol g^-1h^-1）. This work thus identifies a novel approach towards metal free photocatalysts for CO2 photoreduction.
