Doping engineering is an effective strategy for graphitic carbon nitride(g-C3N4)to improve its photocat-alytic hydrogen evolution reaction(HER)performance.In this work,a novel nitrogen and sulfur co-doped g-C_(3...Doping engineering is an effective strategy for graphitic carbon nitride(g-C3N4)to improve its photocat-alytic hydrogen evolution reaction(HER)performance.In this work,a novel nitrogen and sulfur co-doped g-C3N4(N,S-g-C3N4)is elaborately designed on the basis of theoretical predictions of first-principle density functional theory(DFT).The calculated Gibbs free energy of adsorbed hydrogen(ΔGH∗)for N,S-g-C3N4 at the N-doping active sites is extremely close to zero(0.01 eV).Inspired by the theoretical predictions,the N,S-g-C3N4 is successfully fabricated through ammonia-rich pyrolysis synthesis strategy,in which ammonia is in-situ obtained by pyrolyzing melamine.Subsequent characterizations indicate that the N,S-g-C3N4 possesses high specific surface area,outstanding light utilization,good hydrophilicity,and efficient carrier transfer efficiency.Consequently,the N,S-g-C3N4 displays an extremely high H2 evolution rate of 8269.9μmol g−1 h−1,achieves an apparent quantum efficiency(AQE)of 3.24%,and also possesses outsatnding durability.Theoretical calculations further demonstrate that N and S dopants can not only introduce doping energy level to reduce the band gap,but also induce charge redistribution to facilitate hydrogen adsorption,thus promoting the photocatalytic HER process.Moreover,femtosecond transient absorption(fs-TA)spectroscopy further corroborates the efficient photogenerated carrier transport of N,S-g-C3N4.This research highlights a promising and reliable strategy to achieve superior photocatalytic activity,and exhibits significant guidance for precise designing high-efficiency photocatalysts.展开更多
Photocatalytic H2production from water splitting is a promising candidate for solving the increasing energy crisis and environmental issues.Herein we report a novel g-C3N4/Ag InxSyS-scheme heterojunctio...Photocatalytic H2production from water splitting is a promising candidate for solving the increasing energy crisis and environmental issues.Herein we report a novel g-C3N4/Ag InxSyS-scheme heterojunction photocatalyst for water splitting into stoichiometric H2and H2O2under visible light.The catalyst was prepared by depositing 3D bimetallic sulfide(Ag InxSy)nanotubes onto 2D g-C3N4nanosheets.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 H2evolution rate up to 237μmol g-1h-1.Furthermore,suitable band alignment enables simultaneous H2and H2O2production in a 1:1 stoichiometric ratio.H2and H2O2were evolved on the conduction band of g-C3N4and on the valance band of Ag InxSy,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
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
Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to real...Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to realize carbon-free hydrogen production remains a challenge.Heterojunction photocatalysts with well-defined dimensionality and perfectly matched interfaces are promising for achieving highly efficient solar-to-hydrogen conversion.Herein,we report the fabrication of a novel type of protonated graphitic carbon nitride(PCN)/Ti3C2 MXene heterojunctions with strong interfacial interactions.As expected,the two-dimensional(2D)PCN/2D Ti3C2 MXene interface heterojunction achieves a highly improved hydrogen evolution rate(2181μmol∙g‒1)in comparison with bulk g-C3N4(393μmol∙g‒1)and protonated g-C3N4(816μmol∙g‒1).The charge-regulated surfaces of PCN and the accelerated charge transport at the face-to-face 2D/2D Schottky heterojunction interface are the major contributors to the excellent hydrogen evolution performance of the composite photocatalyst.展开更多
Modification of nickel sulfide cocatalysts is considered to be a promising approach for efficient enhancement of the photocatalytic hydrogen production performance of g-C3N4.Providing more NiS cocatalyst to function a...Modification of nickel sulfide cocatalysts is considered to be a promising approach for efficient enhancement of the photocatalytic hydrogen production performance of g-C3N4.Providing more NiS cocatalyst to function as active sites of g-C3N4 is still highly desirable.To realize this goal,in this work,a facile sulfur-mediated photodeposition approach was developed.Specifically,photogenerated electrons excited by visible light reduce the S molecules absorbed on g-C3N4 surface to S^2‒,and subsequently NiS cocatalyst is formed in situ on the g-C3N4 surface by a combination of Ni2+and S2‒due to their small solubility product constant(Ksp=3.2×10^‒19).This approach has several advantages.The NiS cocatalyst is clearly in situ deposited on the photogenerated electron transfer sites of g-C3N4,and thus provides more active sites for H2 production.In addition,this method utilizes solar energy with mild reaction conditions at room temperature.Consequently,the synthesized NiS/g-C3N4 photocatalyst achieves excellent hydrogen generation performance with the performance of the optimal sample(244μmol h^‒1 g^‒1)close to that of 1 wt%Pt/g-C3N4(316μmol h^‒1 g^‒1,a well-known excellent photocatalyst).More importantly,the present sulfur-mediated photodeposition route is versatile and facile and can be used to deposit various metal sulfides such as CoSx,CuSx and AgSx on the g-C3N4 surface,and all the resulting metal sulfide-modified g-C3N4 photocatalysts exhibit improved H2-production performance.Our study offers a novel insight for the synthesis of high-efficiency photocatalysts.展开更多
A possible mechanism for boosting the visible-light photoactivities of graphitic carbon nitride(g-C3N4)nanosheets for CO2 reduction via coupling with the electron donor Co-metal-organic framework(MOF)is proposed in th...A possible mechanism for boosting the visible-light photoactivities of graphitic carbon nitride(g-C3N4)nanosheets for CO2 reduction via coupling with the electron donor Co-metal-organic framework(MOF)is proposed in this study.Specifically,Co-MOF as an electron donor is capable of transferring the photogenerated electrons in the lowest unoccupied molecular orbital(LUMO)to the conduction band of g-C3N4 to facilitate charge separation.As expected,the prepared Co-MOF/g-C3N4 nanocomposites display excellent visible-light-driven photocatalytic CO2 reduction activities.The CO production rate of 6.75μmol g–1 h–1 and CH4 evolution rate of 5.47μmol g–1 h–1 are obtained,which are approximately 2 times those obtained with the original g-C3N4 under the same conditions.Based on a series of analyses,it is shown that the introduction of Co-MOF not only broadens the range of visible-light absorption but also enhances the charge separation,which improves the photocatalytic activity of g-C3N4 to a higher level.In particular,the hydroxyl radical(·OH)experiment was operated under 590 nm(single-wavelength)irradiation,which further proved that the photogenerated electrons in the LUMO of Co-MOF can successfully migrate to g-C3N4.This work may provide an important strategy for the design of highly efficient g-C3N4-based photocatalysts for CO2 reduction.展开更多
The unique heterojunction photocatalyst of graphite carbon nitride (g-C3N4) modified ultrafine TiO2 (g-C3N4/TiO2) was successfully fabricated by electrochemical etching and co-annealing method. Howev...The unique heterojunction photocatalyst of graphite carbon nitride (g-C3N4) modified ultrafine TiO2 (g-C3N4/TiO2) was successfully fabricated by electrochemical etching and co-annealing method. However, the effects of various environmental factors on the degradation of TC by g-C3N4/TiO2 and the internal reaction mechanism are still unclear. In this study, the effects of initial pH, anions, and cations on the photocatalytic degradation of tetracycline hydrochloride (TC) by g-C3N4/TiO2 were systematically explored, and the scavenging experiment and intermediate detection were conducted to better reveal the mechanism on photocatalytic degradation of TC. The results showed that the removal efficiency of photocatalytic degradation of TC by g-C3N4/TiO2 could reach 99.04% under Xenon lamp irradiation within 120 min. The unique g-C3N4/TiO2 heterojunction photocatalyst showed excellent photocatalytic performance for the degradation of TC at pH 3~7, and possesses outstanding anti-interference ability to NO3-, Cl-, Na+, Ca2+ and Mg2+ ions in natural waters during the photocatalytic degradation TC process. Superoxide radicals (O2·-) and hydroxyl radicals (·OH) were proved as the main reactive species for TC degradation, and the possible mechanism of the unique photocatalytic system for g-C3N4/TiO2 was also proposed. The above results can provide a reliable basis and theoretical guidance for the design and application of visible photocatalyst with high activity to degrade the actual wastewater containing TC.展开更多
基金supported by the National Natural Science Foun-dation of China(No.62004143)the Key R&D Program of Hubei Province(No.2022BAA084)the Natural Science Foundation of Hubei Province(No.2021CFB133).
摘要Doping engineering is an effective strategy for graphitic carbon nitride(g-C3N4)to improve its photocat-alytic hydrogen evolution reaction(HER)performance.In this work,a novel nitrogen and sulfur co-doped g-C3N4(N,S-g-C3N4)is elaborately designed on the basis of theoretical predictions of first-principle density functional theory(DFT).The calculated Gibbs free energy of adsorbed hydrogen(ΔGH∗)for N,S-g-C3N4 at the N-doping active sites is extremely close to zero(0.01 eV).Inspired by the theoretical predictions,the N,S-g-C3N4 is successfully fabricated through ammonia-rich pyrolysis synthesis strategy,in which ammonia is in-situ obtained by pyrolyzing melamine.Subsequent characterizations indicate that the N,S-g-C3N4 possesses high specific surface area,outstanding light utilization,good hydrophilicity,and efficient carrier transfer efficiency.Consequently,the N,S-g-C3N4 displays an extremely high H2 evolution rate of 8269.9μmol g−1 h−1,achieves an apparent quantum efficiency(AQE)of 3.24%,and also possesses outsatnding durability.Theoretical calculations further demonstrate that N and S dopants can not only introduce doping energy level to reduce the band gap,but also induce charge redistribution to facilitate hydrogen adsorption,thus promoting the photocatalytic HER process.Moreover,femtosecond transient absorption(fs-TA)spectroscopy further corroborates the efficient photogenerated carrier transport of N,S-g-C3N4.This research highlights a promising and reliable strategy to achieve superior photocatalytic activity,and exhibits significant guidance for precise designing high-efficiency photocatalysts.
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)。
摘要Photocatalytic H2production from water splitting is a promising candidate for solving the increasing energy crisis and environmental issues.Herein we report a novel g-C3N4/Ag InxSyS-scheme heterojunction photocatalyst for water splitting into stoichiometric H2and H2O2under visible light.The catalyst was prepared by depositing 3D bimetallic sulfide(Ag InxSy)nanotubes onto 2D g-C3N4nanosheets.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 H2evolution rate up to 237μmol g-1h-1.Furthermore,suitable band alignment enables simultaneous H2and H2O2production in a 1:1 stoichiometric ratio.H2and H2O2were evolved on the conduction band of g-C3N4and on the valance band of Ag InxSy,respectively.The novel 3D-on-2D configuration for heterojunction construction proposed in this work provided alternative research ideas toward photocatalytic reaction.
摘要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.
摘要Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to realize carbon-free hydrogen production remains a challenge.Heterojunction photocatalysts with well-defined dimensionality and perfectly matched interfaces are promising for achieving highly efficient solar-to-hydrogen conversion.Herein,we report the fabrication of a novel type of protonated graphitic carbon nitride(PCN)/Ti3C2 MXene heterojunctions with strong interfacial interactions.As expected,the two-dimensional(2D)PCN/2D Ti3C2 MXene interface heterojunction achieves a highly improved hydrogen evolution rate(2181μmol∙g‒1)in comparison with bulk g-C3N4(393μmol∙g‒1)and protonated g-C3N4(816μmol∙g‒1).The charge-regulated surfaces of PCN and the accelerated charge transport at the face-to-face 2D/2D Schottky heterojunction interface are the major contributors to the excellent hydrogen evolution performance of the composite photocatalyst.
摘要Modification of nickel sulfide cocatalysts is considered to be a promising approach for efficient enhancement of the photocatalytic hydrogen production performance of g-C3N4.Providing more NiS cocatalyst to function as active sites of g-C3N4 is still highly desirable.To realize this goal,in this work,a facile sulfur-mediated photodeposition approach was developed.Specifically,photogenerated electrons excited by visible light reduce the S molecules absorbed on g-C3N4 surface to S^2‒,and subsequently NiS cocatalyst is formed in situ on the g-C3N4 surface by a combination of Ni2+and S2‒due to their small solubility product constant(Ksp=3.2×10^‒19).This approach has several advantages.The NiS cocatalyst is clearly in situ deposited on the photogenerated electron transfer sites of g-C3N4,and thus provides more active sites for H2 production.In addition,this method utilizes solar energy with mild reaction conditions at room temperature.Consequently,the synthesized NiS/g-C3N4 photocatalyst achieves excellent hydrogen generation performance with the performance of the optimal sample(244μmol h^‒1 g^‒1)close to that of 1 wt%Pt/g-C3N4(316μmol h^‒1 g^‒1,a well-known excellent photocatalyst).More importantly,the present sulfur-mediated photodeposition route is versatile and facile and can be used to deposit various metal sulfides such as CoSx,CuSx and AgSx on the g-C3N4 surface,and all the resulting metal sulfide-modified g-C3N4 photocatalysts exhibit improved H2-production performance.Our study offers a novel insight for the synthesis of high-efficiency photocatalysts.
基金supported by the National Natural Science Foundation of China(21871079,21501052)the Outstanding Youth Project of Natural Science Foundation of Heilongjiang Province(YQ2019B006)~~
摘要A possible mechanism for boosting the visible-light photoactivities of graphitic carbon nitride(g-C3N4)nanosheets for CO2 reduction via coupling with the electron donor Co-metal-organic framework(MOF)is proposed in this study.Specifically,Co-MOF as an electron donor is capable of transferring the photogenerated electrons in the lowest unoccupied molecular orbital(LUMO)to the conduction band of g-C3N4 to facilitate charge separation.As expected,the prepared Co-MOF/g-C3N4 nanocomposites display excellent visible-light-driven photocatalytic CO2 reduction activities.The CO production rate of 6.75μmol g–1 h–1 and CH4 evolution rate of 5.47μmol g–1 h–1 are obtained,which are approximately 2 times those obtained with the original g-C3N4 under the same conditions.Based on a series of analyses,it is shown that the introduction of Co-MOF not only broadens the range of visible-light absorption but also enhances the charge separation,which improves the photocatalytic activity of g-C3N4 to a higher level.In particular,the hydroxyl radical(·OH)experiment was operated under 590 nm(single-wavelength)irradiation,which further proved that the photogenerated electrons in the LUMO of Co-MOF can successfully migrate to g-C3N4.This work may provide an important strategy for the design of highly efficient g-C3N4-based photocatalysts for CO2 reduction.
基金financially supported by National Natural Science Foundation of China (Nos. 52070107, 51678323)Natural Science Foundation of Shandong Province (Nos. ZR2019MD012,ZR2017MEE026)+1 种基金Support Plan on Youth Innovation Science and Technology for Higher Education of Shandong Province (No.2019KJD014)Natural Science Foundation of Heilongjiang Province (No. B2015024)。
摘要The unique heterojunction photocatalyst of graphite carbon nitride (g-C3N4) modified ultrafine TiO2 (g-C3N4/TiO2) was successfully fabricated by electrochemical etching and co-annealing method. However, the effects of various environmental factors on the degradation of TC by g-C3N4/TiO2 and the internal reaction mechanism are still unclear. In this study, the effects of initial pH, anions, and cations on the photocatalytic degradation of tetracycline hydrochloride (TC) by g-C3N4/TiO2 were systematically explored, and the scavenging experiment and intermediate detection were conducted to better reveal the mechanism on photocatalytic degradation of TC. The results showed that the removal efficiency of photocatalytic degradation of TC by g-C3N4/TiO2 could reach 99.04% under Xenon lamp irradiation within 120 min. The unique g-C3N4/TiO2 heterojunction photocatalyst showed excellent photocatalytic performance for the degradation of TC at pH 3~7, and possesses outstanding anti-interference ability to NO3-, Cl-, Na+, Ca2+ and Mg2+ ions in natural waters during the photocatalytic degradation TC process. Superoxide radicals (O2·-) and hydroxyl radicals (·OH) were proved as the main reactive species for TC degradation, and the possible mechanism of the unique photocatalytic system for g-C3N4/TiO2 was also proposed. The above results can provide a reliable basis and theoretical guidance for the design and application of visible photocatalyst with high activity to degrade the actual wastewater containing TC.