Graphitic carbon nitride nanosheets(CNNs)become the most promising member in the carbon nitride family benefitted from their two-dimensional structural features.Recently,great endeavors have been made in the synthesis...Graphitic carbon nitride nanosheets(CNNs)become the most promising member in the carbon nitride family benefitted from their two-dimensional structural features.Recently,great endeavors have been made in the synthesis and modification of CNNs to improve their photocatalytic properties,and many exciting progresses have been gained.In order to elucidate the fundamentals of CNNs based catalysts and provide the insights into rational design of photocatalysis system,we describe recent progress made in CNNs preparation strategies and their applications in this review.Firstly,the physicochemical properties of CNNs are briefly introduced.Secondly,the synthesis approaches of CNNs are reviewed,including top-down stripping strategies(thermal,gas,liquid,and composite stripping)and bottom-up precursor molecules design strategies(solvothermal,template,and supramolecular self-assembly method).Subsequently,the modification strategies based on CNNs in recent years are discussed,including crystal structure design,doping,surface functionalization,constructing 2D heterojunction,and anchoring single-atom.Then the multifunctional applications of g-C_(3)N_(4) nanosheet based materials in photocatalysis including H_(2) evolution,O_(2) evolution,overall water splitting,H_(2)O_(2) production,CO_(2) reduction,N_(2) fixation,pollutant removal,organic synthesis,and sensing are highlighted.Finally,the opportunities and challenges for the development of high-performance CNNs photocatalytic systems are also prospected.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
In this study, the effect of reduced graphene oxide(rGO) on interconnected Co_3O_4 nanosheets and the improved supercapacitive behaviors is reported. By optimizing the experimental parameters, we achieved a specific c...In this study, the effect of reduced graphene oxide(rGO) on interconnected Co_3O_4 nanosheets and the improved supercapacitive behaviors is reported. By optimizing the experimental parameters, we achieved a specific capacitance of ~1016.4 F g^(-1) for the Co_3O_4/rGO/NF(nickel foam) system at a current density of 1 A g^(-1). However, the Co_3O_4/NF structure without rGO only delivers a specific capacitance of ~520.0 F g^(-1)at the same current density. The stability test demonstrates that Co_3O_4/rGO/NF retains ~95.5% of the initial capacitance value even after 3000 charge–discharge cycles at a high current density of 7 A g^(-1). Further investigation reveals that capacitance improvement for the Co_3O_4/rGO/NF structure is mainly because of a higher specific surface area(~87.8 m^2g^(-1))and a more optimal mesoporous size(4–15 nm) compared to the corresponding values of 67.1 m^2g^(-1) and 6–25 nm,respectively, for the Co_3O_4/NF structure. rGO and the thinner Co_3O_4 nanosheets benefit from the strain relaxation during the charge and discharge processes, improving the cycling stability of Co_3O_4/rGO/NF.展开更多
In this study,MnCo2O4 nanosheets were proposed to be utilized as an electrode material for supercapacitors.A two-step hydrothermal method with post-annealing treatment was employed in preparation of the nanostructures...In this study,MnCo2O4 nanosheets were proposed to be utilized as an electrode material for supercapacitors.A two-step hydrothermal method with post-annealing treatment was employed in preparation of the nanostructures.MnCo2O4 electrode delivered a high specific capacitance of 2000 F g^-1 at 0.5 A g^-1,remarkable high-rate capability of 1150 F g^-1 at 20 A g^-1,and an excellent cycling stability of 92.3%at 5 A g^-1 after 5000 cycles.It is found that a three-electrode supercapacitor based on MnCo2O4 exhibits a promising electrochemical performance,better than the other similar materials,benefited from the synergistic effects of MnCo2O4 nanosheets.In fact,the self-assembly of nanosheets structure with high specific surface area and mesoporous structure can potentially enhance the electrochemical performance of supercapacitors.展开更多
PtPd bimetallic alloy nanoparticle (NP)-modified graphitic carbon nitride (g-C3N4) nanosheet photocatalysts were synthesized via chemical deposition precipitation. Characterization of the photocatalytic H2 evolution o...PtPd bimetallic alloy nanoparticle (NP)-modified graphitic carbon nitride (g-C3N4) nanosheet photocatalysts were synthesized via chemical deposition precipitation. Characterization of the photocatalytic H2 evolution of the g-C3N4 nanosheets shows that it was significantly enhanced when PtPd alloy NPs were introduced as a co-catalyst. The 0.2 wt% PtPd/g-C3N4 composite photocatalyst gave a maximum H2 production rate of 1600.8 μmol g^–1 h^–1. Furthermore, when K2HPO4 was added to the reaction system, the H2 production rate increased to 2885.0 μmol g^–1 h^–1. The PtPd/g-C3N4 photocatalyst showed satisfactory photocatalytic stability and was able to maintain most of its photocatalytic activity after four experimental photocatalytic cycles. In addition, a possible mechanism for the enhanced photocatalytic activity was proposed and verified by various photoelectric techniques. These results demonstrate that the synergistic effect between PtPd and g-C3N4 helps to greatly improve the photocatalytic activity of the composite photocatalyst.展开更多
Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO_4/WO_3 nanocomposite powder.The particle morphology,crystalline size,forming course,chem...Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO_4/WO_3 nanocomposite powder.The particle morphology,crystalline size,forming course,chemical composition and phase structure of the powder were studied by SEM,TEM,DTA-TG,IR and XRD,respectively.Results show that the powder is homogeneous,spherical and nano-aggregated.展开更多
Exfoliation of bulk graphitic carbon nitride(g‐C3N4)into two‐dimensional(2D)nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g‐C3N4 nanosheets(CN)have larger spe...Exfoliation of bulk graphitic carbon nitride(g‐C3N4)into two‐dimensional(2D)nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g‐C3N4 nanosheets(CN)have larger specific surface areas and more reaction sites.In addition,poly‐o‐phenylenediamine(PoPD)can improve the electrical conductivity and photocatalytic activity of semiconductor materials.Here,the novel efficient composite PoPD/AgCl/g‐C3N4 nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach.The obtained photocatalysts have larger specific surface areas and could achieve better visible‐light response.However,silver chloride(AgCl)is susceptible to agglomeration and photocorrosion.The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density,which is three times that of CN.Obviously enhanced photocatalytic activities of PoPD/AgCl/g‐C3N4 are revealed through the photodegradation of tetracycline.The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly.Furthermore,.O2^-and h+are the main active species,which are confirmed through a trapping experiment and ESR spin‐trap technique.Therefore,the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst,in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles.This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues.展开更多
In this study,the sulfur-doped porous g-C_(3)N_(4) nanosheets(CN-T-U 1.75)were synthesized successfully by onestep calcination utilizing urea and thiourea as precursors.Under visible light irradiation,CN-T-U 1.75 show...In this study,the sulfur-doped porous g-C_(3)N_(4) nanosheets(CN-T-U 1.75)were synthesized successfully by onestep calcination utilizing urea and thiourea as precursors.Under visible light irradiation,CN-T-U 1.75 showed remarkable photocatalytic activity for Rhodamine B(RhB)degradation with a kinetic reaction rate constant of 0.01838 min^(-1).The characterization analysis indicated that CN-T-U 1.75 had a higher specific surface area and the doping altered the energy band structure.This work offers a new viewpoint on modifying the band structure of a photocatalyst using a doping strategy,as well as new insights into the generation routes of active species involved in the photocatalytic process.展开更多
Engineering the electronic properties of semiconductor-based photocatalysts using elemental doping is an effective approach to improve their catalytic activity.Nevertheless,there still remain contradictions regarding ...Engineering the electronic properties of semiconductor-based photocatalysts using elemental doping is an effective approach to improve their catalytic activity.Nevertheless,there still remain contradictions regarding the role of the dopants played in photocatalysis.Herein,ultrathin ZnIn_(2)S_(4)(ZIS) nanosheets with oxygen doping were synthesized by a one-pot solvothermal method.XRD,XPS and Raman spectral measurements support the presence of lattice oxygen in the oxygen-doped ZIS(O-ZIS) sample.With optimum doping of oxygen,the ultrathin O-ZIS nanosheets show enhanced CO_(2)-to-CO conversion activity with a CO_(2)-evolving rate of 1680 μmol h^(-1) g^(-1) under visible light irradiation,which is about 7 times higher than that of the pristine ZIS.First-principle calculations support that doping of oxygen in the lattice of ZnIn_(2)S_(4) nanosheets plays a key role in tuning its electronic properties.The remarkable photocatalytic performance of O-ZIS can be assigned to a synergistic consequence of a unique ultrathin-layered structure and an upward shift of the conduction band minimum(CBM) caused by the oxygen doping into ZIS and the quantum confinement effect(QCE) induced by the decreased particle size after doping as well as to the improved charge separation efficiency.The present work offers a simple elemental doping method to promote charge separation at atomic level and illustrates the roles played by oxygen doping in photocatalysis,giving new insights into highly efficient artificial photosynthesis.展开更多
Structure manipulation of photocatalysts at an atomic scale is a promising way to improve its photocatalytic performance.Herein,we realize the anchoring of single Ni atoms on the ZnIn_(2)S_(4) nanosheets with rich sul...Structure manipulation of photocatalysts at an atomic scale is a promising way to improve its photocatalytic performance.Herein,we realize the anchoring of single Ni atoms on the ZnIn_(2)S_(4) nanosheets with rich sulfur vacancies.Experimental results demonstrate that single Ni atoms induce the formation of NiO-M(Zn/In) atomic interface,which can efficiently promote the carriers separation and prolong the carrier life time.In addition,in situ electron spin resonance spectroscopy(ESR) confirms that the single Ni atoms act as an electron trapping center for protons reduction.As a result,the single Ni atoms decorated ZnIn_(2)S_(4) nanosheets with rich sulfur vacancies(Ni/ZnIn_(2)S_(4)-RVs) shows a hydrogen evolution rate up to 89.4 μmol h^(-1), almost 5.7 and 2.3 times higher compared to that of ZnIn_(2)S_(4) nanosheets with poor sulfur vacancies and rich sulfur vacancies(denoted as ZnIn_(2)S_(4)-PVs and ZnIn_(2)S_(4)-RVs).This work opens up a new perspective manipulating the single-atom cocatalyst and sulfur vacancy on sulfide supports for improving photocatalytic hydrogen evolution.展开更多
H＋-restacked nanosheets and nanoscrolls peeled from K4Nb6O17 display different structures and surface characters. The two restacked samples with increased surface areas have an amazing visible-light response for the ...H＋-restacked nanosheets and nanoscrolls peeled from K4Nb6O17 display different structures and surface characters. The two restacked samples with increased surface areas have an amazing visible-light response for the photodegradation of dyes, which is superior to commercial TiO2 （P25） and Nb205. By comparison, H＋/nanosheets have a relatively faster photodegradation rate originated from large and smooth basal plane. The work reveals that dye adsorbed on the unfolded nanosheets can effectively harvest sunlight. Due to facile preparation, low-cost and high photocatalytic efficiency, H＋/nanosheets and H＋/nanoscrolls might be used for the visible light-driven degradation of organic dyes as a substitute for TiO2 in industry.展开更多
Graphitic carbon nitride(g-C_(3)N_(4)) is a fascinating photocatalyst for solar energy utilization in photo-catalysis.Nevertheless,it often suffers from moderate photo-catalytic activity due to its low specific surfac...Graphitic carbon nitride(g-C_(3)N_(4)) is a fascinating photocatalyst for solar energy utilization in photo-catalysis.Nevertheless,it often suffers from moderate photo-catalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons upon photo-excitation.Herein,we overcome the bottlenecks by constructing a porous g-C_(3)N_(4) nanosheet(PCNS)through a simple thermal oxidation etching method.Benefited from its porous layer structure,the obtained PCNS exhibits large specific surface area,efficient separation of photogenerated charge carriers,as well as high exposure of active sites.As a result,it is robust and universal in visible light-driven dehydrogenation of alcohols in water under oxidant-free condition.Almost quantitative yields(>99%)of various valuable carbonyl compounds were obtained over PCNS,while bulk g-C_(3)N_(4) was far less efficient.Moreover,the photo-catalyst was highly stable and could be facilely recovered from the aqueous system for efficient reuse.The easy preparation and excellent performance made PCNS a promising and competitive photocatalyst for the solar applications.展开更多
Energetic molecular perovskites have attracted widespread attention in the fields of energy materials due to their high detonation performance.In this work,we reported the effect of MgCo_(2)O_(4) nanosheets on the the...Energetic molecular perovskites have attracted widespread attention in the fields of energy materials due to their high detonation performance.In this work,we reported the effect of MgCo_(2)O_(4) nanosheets on the thermal decomposition of ammonium perchlorate(NH_(4)ClO_(4),AP)-based energetic molecular perovskites(AP-based energetic molecular perovskites).The morphology and structure of the MgCo_(2)O_(4) nanosheets were characterized.And their catalytic effect on the thermal decomposition of AP-based energetic molecular perovskites(H_2pz)[NH_(4)(ClO_(4))_(3)](PAP-4),(H_2dabco)[NH_(4)(ClO_(4))_(3)](DAP-4),(H_2mpz)[NH_(4)(ClO_(4))_(3)](PAP-M_(4)),and (H_2hpz)[NH_(4)(ClO_(4))_(3)](PAP-H_(4)) was analyzed.The results showed that MgCo_(2)O_(4) nanosheets had excellent intrinsically catalytic performance towards enhancing the thermal decomposition of AP-based energetic molecular perovskites.After adding MgCo_(2)O_(4) nanosheets,the thermal decomposition peak temperatures of PAP-4,DAP-4,PAP-M_(4),and PAP-H_(4) had been reduced by35.7℃,48.4℃,37.9℃,and 43.6℃,respectively.And the activation energy(Ea)of the thermal decomposition of AP-based energetic molecular perovskites had been reduced,the Eaof PAP-H_(4) decreased by 46.4 kJ/mol at most among them.The catalytic mechanism of MgCo_(2)O_(4) nanosheets for AP-based energetic molecular perovskites is analyzed.This work provides a reference for the future application of AP-based energetic molecular perovskites.展开更多
Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction(ORR).The...Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction(ORR).The obtained C4N nanosheets are semi-conductive with a small band gap of 1.41 eV and contain abundant pyrazine-nitrogen moieties uniformly distributed throughout C4N.Density function theory calculations reveal that the intramolecular charge transfer induced by pyrazine-nitrogen in C4N enables effective charge redistribution to activate the conjugated structure and facilitate the oxygen adsorption,while the exfoliated sheet-like C4N formation renders improved electrochemical active surface area and results in high exposure of active sites.As a result,despite the bulk C4N is not active,the sheet-like C4N yield markedly improved ORR performance,even on a par with the commercial Pt/C catalyst.Our recent findings not only enrich the family members of two-dimensional conjugated polymer nanosheets but also open up new opportunity to explore new metal-free organic polymeric materials for efficient oxygen reduction catalysis and beyond.展开更多
The development of zinc ion batteries (ZIBs) with large capacity,high rate,and durable cathode material is a crucial and urgent task.Ni Co_(2)O_(4)(NCO) has received ever-growing interest as a potential cathode materi...The development of zinc ion batteries (ZIBs) with large capacity,high rate,and durable cathode material is a crucial and urgent task.Ni Co_(2)O_(4)(NCO) has received ever-growing interest as a potential cathode material for ZIBs,owing to the high theoretical capacity,rich source,cost-effective,and versatile redox nature.However,due to the slow dynamics of the NCO electrodes,its practical application in highperformance systems is severely limited.Herein,we report an electron density modulated NCO nanosheets (N-NCO NSs) with high-kinetics Zn^(2+)-storage capability as an additive-free cathode for flexible all-solid-state (ASS) ZIBs.By virtue of the enhanced electronic conductivity,improved reaction kinetics,and increased active sites,the optimized N-NCO NSs electrode delivers a high capacity of 357.7 m Ah g^(-1)at 1.0 A g^(-1)and a superior rate capacity of 201.4 m Ah g^(-1)at 20 A g^(-1).More importantly,a flexible ASS ZIBs device is manufactured using a solid polymer electrolyte of a poly (vinylidene fluoride hexafluoropropylene)(PVDF-HFP) film.The flexible ASS ZIBs device shows superb durability with 80.2%capacity retention after 20,000 cycles and works well in the range of-20–70℃.Furthermore,the flexible ASS ZIBs achieves an impressive energy density as high as 578.1 W h kg^(-1)with a peak power density of 33.6 k W kg^(-1),substantially outperforming those latest ZIBs.This work could provide valuable insights for constructing high-kinetics and high-capability cathodes with long-term stability for flexible ASS ZIBs.展开更多
The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,whi...The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,which are in situ reduced into Cu nanosheets during electrochemical CO_(2)reduction reaction(ECO_(2)RR).The derived Cu nanosheets demonstrate much higher selectivity for C2H4production than commercial CuO derived Cu powder,with an optimum Faradaic efficiency of 56.2%and a partial current density of C_(2)H_(4)as large as 171.0 mA cm^(-2)in a gas diffusion flow cell.The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5(4–6),which facilitates the formation of^(*)CHO rather than^(*)COH intermediate,meanwhile boosting the C-C coupling reaction of^(*)CO and^(*)CHO intermediates,which are the critical steps for C_(2)H_(4)formation.展开更多
Nanoporous anorthic-phase Sn3O4 nanosheets are successfully fabricated via a hydrothermal process without any additives. With the pH value of the precursor increasing from 2.0 to 11.8, the valence of the precursor cha...Nanoporous anorthic-phase Sn3O4 nanosheets are successfully fabricated via a hydrothermal process without any additives. With the pH value of the precursor increasing from 2.0 to 11.8, the valence of the precursor changes from mixed valence （the ratio of Sn2＋ to Sn4＋ is 2.7： 1） to pure bivalent, and the product transformed from Sn3O4 to SnO mesocrystals. When doping SbC13 to the alkaline precursor, the valence of the precursor shows mixed valence with the ratio of Sn2＋ to Sn4＋ being 2.6： I and Sn3O4 is synthesized after the hydrothermal process. The valence state of Sn species in the precursor is the key factor of the formation of Sn3O4. The synthesis mechanism is discussed and proposed. These experimental results expand the knowledge base that can be used to guide technological applications of intermediate tin oxide materials.展开更多
基金supported by the National Natural Science Foundation of China(22172195)Central South University Graduate Students Independent Exploration and Innovation Project(2023ZZTS0736 and 2023ZZTS0760).
文摘Graphitic carbon nitride nanosheets(CNNs)become the most promising member in the carbon nitride family benefitted from their two-dimensional structural features.Recently,great endeavors have been made in the synthesis and modification of CNNs to improve their photocatalytic properties,and many exciting progresses have been gained.In order to elucidate the fundamentals of CNNs based catalysts and provide the insights into rational design of photocatalysis system,we describe recent progress made in CNNs preparation strategies and their applications in this review.Firstly,the physicochemical properties of CNNs are briefly introduced.Secondly,the synthesis approaches of CNNs are reviewed,including top-down stripping strategies(thermal,gas,liquid,and composite stripping)and bottom-up precursor molecules design strategies(solvothermal,template,and supramolecular self-assembly method).Subsequently,the modification strategies based on CNNs in recent years are discussed,including crystal structure design,doping,surface functionalization,constructing 2D heterojunction,and anchoring single-atom.Then the multifunctional applications of g-C_(3)N_(4) nanosheet based materials in photocatalysis including H_(2) evolution,O_(2) evolution,overall water splitting,H_(2)O_(2) production,CO_(2) reduction,N_(2) fixation,pollutant removal,organic synthesis,and sensing are highlighted.Finally,the opportunities and challenges for the development of high-performance CNNs photocatalytic systems are also prospected.
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)~~
文摘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 from the National Natural Science Foundation of China (Grant Nos.: 61376068, 11304132, 11304133, and 11405144)the Specialized Research Fund of the Doctoral Program of Higher Education (Grant Nos.: 20120211120003 and 20130211120009)the Fundamental Research Funds for the Central Universities (Grant Nos.: lzujbky2013-36 and lzujbky-2014-30)
文摘In this study, the effect of reduced graphene oxide(rGO) on interconnected Co_3O_4 nanosheets and the improved supercapacitive behaviors is reported. By optimizing the experimental parameters, we achieved a specific capacitance of ~1016.4 F g^(-1) for the Co_3O_4/rGO/NF(nickel foam) system at a current density of 1 A g^(-1). However, the Co_3O_4/NF structure without rGO only delivers a specific capacitance of ~520.0 F g^(-1)at the same current density. The stability test demonstrates that Co_3O_4/rGO/NF retains ~95.5% of the initial capacitance value even after 3000 charge–discharge cycles at a high current density of 7 A g^(-1). Further investigation reveals that capacitance improvement for the Co_3O_4/rGO/NF structure is mainly because of a higher specific surface area(~87.8 m^2g^(-1))and a more optimal mesoporous size(4–15 nm) compared to the corresponding values of 67.1 m^2g^(-1) and 6–25 nm,respectively, for the Co_3O_4/NF structure. rGO and the thinner Co_3O_4 nanosheets benefit from the strain relaxation during the charge and discharge processes, improving the cycling stability of Co_3O_4/rGO/NF.
基金supported by the National Natural Science Foundation of China (51572194)the National Key Research and Development Program of China (2018YFB0105900)
文摘In this study,MnCo2O4 nanosheets were proposed to be utilized as an electrode material for supercapacitors.A two-step hydrothermal method with post-annealing treatment was employed in preparation of the nanostructures.MnCo2O4 electrode delivered a high specific capacitance of 2000 F g^-1 at 0.5 A g^-1,remarkable high-rate capability of 1150 F g^-1 at 20 A g^-1,and an excellent cycling stability of 92.3%at 5 A g^-1 after 5000 cycles.It is found that a three-electrode supercapacitor based on MnCo2O4 exhibits a promising electrochemical performance,better than the other similar materials,benefited from the synergistic effects of MnCo2O4 nanosheets.In fact,the self-assembly of nanosheets structure with high specific surface area and mesoporous structure can potentially enhance the electrochemical performance of supercapacitors.
基金supported by the National Natural Science Foundation of China(51572295,21273285,21003157)the Beijing Nova Program(2008B76)the Science Foundation of China University of Petroleum Beijing(KYJJ2012-06-20 and 2462016YXBS05)~~
文摘PtPd bimetallic alloy nanoparticle (NP)-modified graphitic carbon nitride (g-C3N4) nanosheet photocatalysts were synthesized via chemical deposition precipitation. Characterization of the photocatalytic H2 evolution of the g-C3N4 nanosheets shows that it was significantly enhanced when PtPd alloy NPs were introduced as a co-catalyst. The 0.2 wt% PtPd/g-C3N4 composite photocatalyst gave a maximum H2 production rate of 1600.8 μmol g^–1 h^–1. Furthermore, when K2HPO4 was added to the reaction system, the H2 production rate increased to 2885.0 μmol g^–1 h^–1. The PtPd/g-C3N4 photocatalyst showed satisfactory photocatalytic stability and was able to maintain most of its photocatalytic activity after four experimental photocatalytic cycles. In addition, a possible mechanism for the enhanced photocatalytic activity was proposed and verified by various photoelectric techniques. These results demonstrate that the synergistic effect between PtPd and g-C3N4 helps to greatly improve the photocatalytic activity of the composite photocatalyst.
文摘Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO_4/WO_3 nanocomposite powder.The particle morphology,crystalline size,forming course,chemical composition and phase structure of the powder were studied by SEM,TEM,DTA-TG,IR and XRD,respectively.Results show that the powder is homogeneous,spherical and nano-aggregated.
基金supported by the National Natural Science Foundation of China(21576125,21776117)the China Postdoctoral Science Foundation(2017M611716,2017M611734)+1 种基金the Six talent peaks project of Jiangsu Province(XCL-014)the Zhenjiang Science&Technology Program(SH2016012)~~
文摘Exfoliation of bulk graphitic carbon nitride(g‐C3N4)into two‐dimensional(2D)nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g‐C3N4 nanosheets(CN)have larger specific surface areas and more reaction sites.In addition,poly‐o‐phenylenediamine(PoPD)can improve the electrical conductivity and photocatalytic activity of semiconductor materials.Here,the novel efficient composite PoPD/AgCl/g‐C3N4 nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach.The obtained photocatalysts have larger specific surface areas and could achieve better visible‐light response.However,silver chloride(AgCl)is susceptible to agglomeration and photocorrosion.The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density,which is three times that of CN.Obviously enhanced photocatalytic activities of PoPD/AgCl/g‐C3N4 are revealed through the photodegradation of tetracycline.The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly.Furthermore,.O2^-and h+are the main active species,which are confirmed through a trapping experiment and ESR spin‐trap technique.Therefore,the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst,in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles.This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues.
基金supported by the Liaoning Provincial Natural Fund Mentoring Program Project (2019-ZD-0057)
文摘In this study,the sulfur-doped porous g-C_(3)N_(4) nanosheets(CN-T-U 1.75)were synthesized successfully by onestep calcination utilizing urea and thiourea as precursors.Under visible light irradiation,CN-T-U 1.75 showed remarkable photocatalytic activity for Rhodamine B(RhB)degradation with a kinetic reaction rate constant of 0.01838 min^(-1).The characterization analysis indicated that CN-T-U 1.75 had a higher specific surface area and the doping altered the energy band structure.This work offers a new viewpoint on modifying the band structure of a photocatalyst using a doping strategy,as well as new insights into the generation routes of active species involved in the photocatalytic process.
基金financially supported by the National Natural Science Foundation of China(Grants Nos.21976116 and 21902095)Shaanxi Science and Technology Program(2020KWZ005)+3 种基金SAFEA of China(High-end foreign expert project # G20190241013)Natural Foundation of Shaanxi Province(No.2020JQ-711)Group Linkage Program of Alexander-vonHumboldt Foundation of Germanythe scientific research startup fund of Shannxi University of Science and Technology。
文摘Engineering the electronic properties of semiconductor-based photocatalysts using elemental doping is an effective approach to improve their catalytic activity.Nevertheless,there still remain contradictions regarding the role of the dopants played in photocatalysis.Herein,ultrathin ZnIn_(2)S_(4)(ZIS) nanosheets with oxygen doping were synthesized by a one-pot solvothermal method.XRD,XPS and Raman spectral measurements support the presence of lattice oxygen in the oxygen-doped ZIS(O-ZIS) sample.With optimum doping of oxygen,the ultrathin O-ZIS nanosheets show enhanced CO_(2)-to-CO conversion activity with a CO_(2)-evolving rate of 1680 μmol h^(-1) g^(-1) under visible light irradiation,which is about 7 times higher than that of the pristine ZIS.First-principle calculations support that doping of oxygen in the lattice of ZnIn_(2)S_(4) nanosheets plays a key role in tuning its electronic properties.The remarkable photocatalytic performance of O-ZIS can be assigned to a synergistic consequence of a unique ultrathin-layered structure and an upward shift of the conduction band minimum(CBM) caused by the oxygen doping into ZIS and the quantum confinement effect(QCE) induced by the decreased particle size after doping as well as to the improved charge separation efficiency.The present work offers a simple elemental doping method to promote charge separation at atomic level and illustrates the roles played by oxygen doping in photocatalysis,giving new insights into highly efficient artificial photosynthesis.
基金the support of the National Natural Science Foundation of China(51702087,21673066)the Project funded by the China Postdoctoral Science Foundation(2019M652516)。
文摘Structure manipulation of photocatalysts at an atomic scale is a promising way to improve its photocatalytic performance.Herein,we realize the anchoring of single Ni atoms on the ZnIn_(2)S_(4) nanosheets with rich sulfur vacancies.Experimental results demonstrate that single Ni atoms induce the formation of NiO-M(Zn/In) atomic interface,which can efficiently promote the carriers separation and prolong the carrier life time.In addition,in situ electron spin resonance spectroscopy(ESR) confirms that the single Ni atoms act as an electron trapping center for protons reduction.As a result,the single Ni atoms decorated ZnIn_(2)S_(4) nanosheets with rich sulfur vacancies(Ni/ZnIn_(2)S_(4)-RVs) shows a hydrogen evolution rate up to 89.4 μmol h^(-1), almost 5.7 and 2.3 times higher compared to that of ZnIn_(2)S_(4) nanosheets with poor sulfur vacancies and rich sulfur vacancies(denoted as ZnIn_(2)S_(4)-PVs and ZnIn_(2)S_(4)-RVs).This work opens up a new perspective manipulating the single-atom cocatalyst and sulfur vacancy on sulfide supports for improving photocatalytic hydrogen evolution.
基金supported by the National Natural Science Foundation of China(Grant No.21073084 and 20773065)the Natural Science Foundation of Jiangsu Province(Grant No.BK2011438)+2 种基金973 Project(Grant No.2009CB623504)Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20130091110010)Modern Analysis Center of Nanjing University
文摘H＋-restacked nanosheets and nanoscrolls peeled from K4Nb6O17 display different structures and surface characters. The two restacked samples with increased surface areas have an amazing visible-light response for the photodegradation of dyes, which is superior to commercial TiO2 （P25） and Nb205. By comparison, H＋/nanosheets have a relatively faster photodegradation rate originated from large and smooth basal plane. The work reveals that dye adsorbed on the unfolded nanosheets can effectively harvest sunlight. Due to facile preparation, low-cost and high photocatalytic efficiency, H＋/nanosheets and H＋/nanoscrolls might be used for the visible light-driven degradation of organic dyes as a substitute for TiO2 in industry.
基金financial support provided by the National Natural Science Foundation of China(21676078)the Natural Science Foundation of Hunan Province for Distinguished Young Scholar(2016JJ1013)+1 种基金Scientific Research Fund of Hunan Provincial Education Department(19A323)Science and Technology Planning Project of Hunan Province(2018TP1017)。
文摘Graphitic carbon nitride(g-C_(3)N_(4)) is a fascinating photocatalyst for solar energy utilization in photo-catalysis.Nevertheless,it often suffers from moderate photo-catalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons upon photo-excitation.Herein,we overcome the bottlenecks by constructing a porous g-C_(3)N_(4) nanosheet(PCNS)through a simple thermal oxidation etching method.Benefited from its porous layer structure,the obtained PCNS exhibits large specific surface area,efficient separation of photogenerated charge carriers,as well as high exposure of active sites.As a result,it is robust and universal in visible light-driven dehydrogenation of alcohols in water under oxidant-free condition.Almost quantitative yields(>99%)of various valuable carbonyl compounds were obtained over PCNS,while bulk g-C_(3)N_(4) was far less efficient.Moreover,the photo-catalyst was highly stable and could be facilely recovered from the aqueous system for efficient reuse.The easy preparation and excellent performance made PCNS a promising and competitive photocatalyst for the solar applications.
基金the National Natural Science Foundation of China(Grant No.21975227)the Found of National defence Sci&Tech Laboratory(Grant No.6142602210306)。
文摘Energetic molecular perovskites have attracted widespread attention in the fields of energy materials due to their high detonation performance.In this work,we reported the effect of MgCo_(2)O_(4) nanosheets on the thermal decomposition of ammonium perchlorate(NH_(4)ClO_(4),AP)-based energetic molecular perovskites(AP-based energetic molecular perovskites).The morphology and structure of the MgCo_(2)O_(4) nanosheets were characterized.And their catalytic effect on the thermal decomposition of AP-based energetic molecular perovskites(H_2pz)[NH_(4)(ClO_(4))_(3)](PAP-4),(H_2dabco)[NH_(4)(ClO_(4))_(3)](DAP-4),(H_2mpz)[NH_(4)(ClO_(4))_(3)](PAP-M_(4)),and (H_2hpz)[NH_(4)(ClO_(4))_(3)](PAP-H_(4)) was analyzed.The results showed that MgCo_(2)O_(4) nanosheets had excellent intrinsically catalytic performance towards enhancing the thermal decomposition of AP-based energetic molecular perovskites.After adding MgCo_(2)O_(4) nanosheets,the thermal decomposition peak temperatures of PAP-4,DAP-4,PAP-M_(4),and PAP-H_(4) had been reduced by35.7℃,48.4℃,37.9℃,and 43.6℃,respectively.And the activation energy(Ea)of the thermal decomposition of AP-based energetic molecular perovskites had been reduced,the Eaof PAP-H_(4) decreased by 46.4 kJ/mol at most among them.The catalytic mechanism of MgCo_(2)O_(4) nanosheets for AP-based energetic molecular perovskites is analyzed.This work provides a reference for the future application of AP-based energetic molecular perovskites.
基金financial support from the National Natural Science Foundation of China(No.51973240)the Fundamental Research Funds for the Central Universities(Grant No.19lgzd19 and 19lgpy117)+1 种基金China Postdoctoral Science Foundation(No.2019M653176)the Guangdong Yang Fan Innovative&Entepreneurial Research Team Program(Grant No.2016YT03C077)。
文摘Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction(ORR).The obtained C4N nanosheets are semi-conductive with a small band gap of 1.41 eV and contain abundant pyrazine-nitrogen moieties uniformly distributed throughout C4N.Density function theory calculations reveal that the intramolecular charge transfer induced by pyrazine-nitrogen in C4N enables effective charge redistribution to activate the conjugated structure and facilitate the oxygen adsorption,while the exfoliated sheet-like C4N formation renders improved electrochemical active surface area and results in high exposure of active sites.As a result,despite the bulk C4N is not active,the sheet-like C4N yield markedly improved ORR performance,even on a par with the commercial Pt/C catalyst.Our recent findings not only enrich the family members of two-dimensional conjugated polymer nanosheets but also open up new opportunity to explore new metal-free organic polymeric materials for efficient oxygen reduction catalysis and beyond.
基金the Basic and Applied Basic Research Project of Guangdong Province(2019A1515110827)the Science and Technology Planning Project of Guangzhou(202102080169)+3 种基金the Education Commission of Guangdong Province(2019GKTSCX015)the Advanced Functional Materials Scientific Research and Technical Service Team(X20190197)Guangdong Training Programs of Scientific and Technological Innovation for Undergraduates(pdjh2021a0715)the Innovation Training Program for Undergraduate of Hainan Normal University(2021024)。
文摘The development of zinc ion batteries (ZIBs) with large capacity,high rate,and durable cathode material is a crucial and urgent task.Ni Co_(2)O_(4)(NCO) has received ever-growing interest as a potential cathode material for ZIBs,owing to the high theoretical capacity,rich source,cost-effective,and versatile redox nature.However,due to the slow dynamics of the NCO electrodes,its practical application in highperformance systems is severely limited.Herein,we report an electron density modulated NCO nanosheets (N-NCO NSs) with high-kinetics Zn^(2+)-storage capability as an additive-free cathode for flexible all-solid-state (ASS) ZIBs.By virtue of the enhanced electronic conductivity,improved reaction kinetics,and increased active sites,the optimized N-NCO NSs electrode delivers a high capacity of 357.7 m Ah g^(-1)at 1.0 A g^(-1)and a superior rate capacity of 201.4 m Ah g^(-1)at 20 A g^(-1).More importantly,a flexible ASS ZIBs device is manufactured using a solid polymer electrolyte of a poly (vinylidene fluoride hexafluoropropylene)(PVDF-HFP) film.The flexible ASS ZIBs device shows superb durability with 80.2%capacity retention after 20,000 cycles and works well in the range of-20–70℃.Furthermore,the flexible ASS ZIBs achieves an impressive energy density as high as 578.1 W h kg^(-1)with a peak power density of 33.6 k W kg^(-1),substantially outperforming those latest ZIBs.This work could provide valuable insights for constructing high-kinetics and high-capability cathodes with long-term stability for flexible ASS ZIBs.
基金funded by the National Key Research and Development Program of China(2017YFA0700103,2018YFA0704502)the National Natural Science Foundation of China(21703248)staffs in BL11B beamline in Shanghai Synchrotron Radiation Facility(SSRF)for their technical assistance(2020-SSRF-PT-012223 and 2021-SSRF-PT-015319)。
文摘The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,which are in situ reduced into Cu nanosheets during electrochemical CO_(2)reduction reaction(ECO_(2)RR).The derived Cu nanosheets demonstrate much higher selectivity for C2H4production than commercial CuO derived Cu powder,with an optimum Faradaic efficiency of 56.2%and a partial current density of C_(2)H_(4)as large as 171.0 mA cm^(-2)in a gas diffusion flow cell.The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5(4–6),which facilitates the formation of^(*)CHO rather than^(*)COH intermediate,meanwhile boosting the C-C coupling reaction of^(*)CO and^(*)CHO intermediates,which are the critical steps for C_(2)H_(4)formation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21377063,51102250,21203226,and 21205127)the Personnel Training Foundation of Quzhou University(Grant No.BSYJ201412)
文摘Nanoporous anorthic-phase Sn3O4 nanosheets are successfully fabricated via a hydrothermal process without any additives. With the pH value of the precursor increasing from 2.0 to 11.8, the valence of the precursor changes from mixed valence （the ratio of Sn2＋ to Sn4＋ is 2.7： 1） to pure bivalent, and the product transformed from Sn3O4 to SnO mesocrystals. When doping SbC13 to the alkaline precursor, the valence of the precursor shows mixed valence with the ratio of Sn2＋ to Sn4＋ being 2.6： I and Sn3O4 is synthesized after the hydrothermal process. The valence state of Sn species in the precursor is the key factor of the formation of Sn3O4. The synthesis mechanism is discussed and proposed. These experimental results expand the knowledge base that can be used to guide technological applications of intermediate tin oxide materials.
