High stability and efficient charge separation are two critical factors to construct high-performance photocatalysts.Here,an efficient strategy was provided to fabricate the nanocomposite of graphitic carbon nitride/f...High stability and efficient charge separation are two critical factors to construct high-performance photocatalysts.Here,an efficient strategy was provided to fabricate the nanocomposite of graphitic carbon nitride/ferroferric oxide/reduced graphene oxide(g-C_(3)N_(4)/Fe_(3)O_(4)/RGO).The degradation of rhodamine B(RhB)by g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite followed the pseudofirst-order kinetics.The g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite exhibited excellent stability and magnetically separable performance.It was ascertained that the quantum efficiency and separation efficiency of photoexcited charge carriers of g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite were obviously improved.Particularly,the g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite with 3 wt.%RGO presented 100%degradation efficiency under visible light irradiation for 75 min.The remarkable photocatalytic degradation activity is attributed to the synergistic interactions among g-C_(3)N_(4),Fe_(3)O_(4),and RGO,along with the efficient interfacial charge separation.展开更多
The development of efficient, low-cost, for water splitting, particularly those stable, non-noble-metal electrocatalysts that can catalyze both the hydrogen evolution reaction (HER) at the cathode and oxygen evoluti...The development of efficient, low-cost, for water splitting, particularly those stable, non-noble-metal electrocatalysts that can catalyze both the hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode, is a challenge. We have developed a facile method for synthesizing CoSe2 nanoparticles uniformly anchored on carbon fiber paper (CoSe2/CF) via pyrolysis and selenization of in situ grown zeolitic imidazolate framework-67 (ZIF-67). CoSe2/CF shows high and stable catalytic activity in both the HER and OER in alkaline solution. At a low cell potential, i.e., 1.63 V, a water electrolyzer equipped with two CoSe2/CF electrodes gave a water-splitting current of 10 mA.cm-2. At a current of 20 mA-cm-2, it can operate without degradation for 30 h. This study not only offers a cost-effective solution for water splitting but also provides a new strategy for developing various catalytic nanostructures by changing the metal-organic framework precursors.展开更多
Designing electromagnetic wave absorption(EMWA)materials with wide bandwidth,strong absorption,and light weight is still a great challenge for practical applications.Herein,the novel nitrogen doped carbon(NDC)/MoS_(2)...Designing electromagnetic wave absorption(EMWA)materials with wide bandwidth,strong absorption,and light weight is still a great challenge for practical applications.Herein,the novel nitrogen doped carbon(NDC)/MoS_(2) composite with rationally designed composition and structure was developed.The NDC particles were introduced into MoS_(2) nanosheets through the calcination of ZIF-8 precursor and consequent hydrothermal process.A series of characterizations were carried out to investigate the physical properties of the as-prepared nanocomposites.The NDC particles exhibited the shape of rhombic dodecahedron with the size of about 500 nm,which were decorated on flower-shaped MoS_(2) with the size of about 3μm.With the increasing NDC content,the absorbing properties of NDC/MoS_(2) composites increased firstly and then decreased.The features of NDC/MoS_(2) composite including interconnected porous structure,nitrogen dopant,and appropriate electrical conductivity gave rise to the polarization,multiple reflection,multiple scattering,and impedance matching,resulting in the outstanding EMWA performance.With a filler loading ratio of 30 wt.%,the optimized EMWA property can be achieved when the mass ratio of NDC to MoS_(2) was adjusted to be 1:1.At a coating thickness of 3.0 mm,the effective EMWA bandwidth(<−10 dB)reached 6.08 GHz(8.56–14.64 GHz).These satisfactory achievements provide a way for the reasonable design of high-performance EMWA and new ideas for future research on wideband EMWA.展开更多
A highly efficient absorber with features including lightweight, broad bandwidth, and tunable electromagnetic property still remains challenging for practical applications. Herein, the Porphyra-derived porous carbon(P...A highly efficient absorber with features including lightweight, broad bandwidth, and tunable electromagnetic property still remains challenging for practical applications. Herein, the Porphyra-derived porous carbon(PPC) was fabricated via facile procedures of low-temperature pre-carbonization combined with KOH chemical activation. The composition, microstructure, and electromagnetic wave absorption properties of the samples were elucidated based on X-ray diffraction(XRD), Raman, X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), transmission electron microscopy(TEM),Brunauer-Emmer-Teller(BET), and vector network analyzer(VNA). The porosity of PPC can be readily regulated by adjusting activation temperature. The PPC obtained at 750 ℃ was composed of a threedimensional hierarchically porous carbon network. The C and N elements of natural Porphyra were introduced into the carbon skeleton during the carbonization process. The large specific surface, dopants, and three-dimensional hierarchically porous carbon network can effectively improve the impedance matching and dielectric dissipation, leading to an excellent electromagnetic wave absorption performance. Especially, the optimal reflection loss(RL) value reached –57.75 d B at 9.68 GHz with a broad bandwidth(RL< –10 d B) value of 7.60 GHz at 3.5 mm. Overall, the results indicate that the PPC can provide a new way to achieve lightweight, effective, and sustainable absorbers.展开更多
A highly active and stable oxygen evolution reaction (OER) electrocatalyst is critical for hydrogen production from water splitting. Herein, three-dimensional Ni3Sa@graphene@Co9S8 (Ni3S2@G@Co9S8), a sandwich- stru...A highly active and stable oxygen evolution reaction (OER) electrocatalyst is critical for hydrogen production from water splitting. Herein, three-dimensional Ni3Sa@graphene@Co9S8 (Ni3S2@G@Co9S8), a sandwich- structured OER electro-catalyst, was grown in situ on nickel foam; it afforded an enhanced catalytic performance when highly conductive graphene is introduced as an intermediary for enhancing the electron transfer rate and stability. Serving as a free-standing electrocatalytic electrode, Ni3S2@G@Co9S8 presents excellent electrocatalytic activities for OER: A low onset overpotential (2 mA·cm^-2 at 174 mV), large anode current density (10 mA·cm^-2 at an overpotential of 210 mV), low Tafel slope (66 mV·dec^-1), and predominant durability of over 96 h (releasing a current density of N 14 mA·cm^-2 with a low and constant overpotential of 215 mV) in a 1 M KOH solution. This work provides a promising, cost-efficient electrocatalyst and sheds new light on improving the electrochemical performance of composites through enhancing the electron transfer rate and stability by introducing graphene as an intermediary.展开更多
Triangular Ni(HCO3)2 nanosheets were synthesized via a template-free solvothermal method. The phase transition and formation mechanism were explored systematically. Further investigation indicated that the reaction ...Triangular Ni(HCO3)2 nanosheets were synthesized via a template-free solvothermal method. The phase transition and formation mechanism were explored systematically. Further investigation indicated that the reaction time and pH have significant effects on the morphology and size distribution of the triangular Ni(HCO3)2 nanosheets. More interestingly, the resulting product had an ultra-thin structure and high specific surface area, which can effectively accelerate the charge transport during charge--discharge processes. As a result, the triangular Ni(HCO3)2 nanosheets not only exhibited high specific capacitance (1,797 F·g^-1 at 5 A·g^-1 and 1,060 F·g^-1 at 50 A·g^-1), but also showed excellent cycling stability with a high current density (-80% capacitance retention after 5,000 cycles at the current density of 20 A·g^-1).展开更多
The rational design of earth-abundant catalysts with excellent water splitting activities is important to obtain clean fuels for sustainable energy devices. In this study, mixed transition metal oxide nanoparticles en...The rational design of earth-abundant catalysts with excellent water splitting activities is important to obtain clean fuels for sustainable energy devices. In this study, mixed transition metal oxide nanoparticles encapsulated in nitrogendoped carbon (denoted as AB2O4@NC) were developed using a one-pot protocol, wherein a metal-organic complex was adopted as the precursor. As a proof of concept, MnCo2O4@NC was used as an electrocatalyst for water oxidation, and demonstrated an outstanding electrocatalytic activity with low overpotential to achieve a current density of 10 mA·cm^-1 0/10 = 287 mV), small Tafel slope (55 mV·dec^-1), and high stability (96% retention after 20 h). The excellent electrochemical performance benefited from the synergistic effects of the MnCo2O4 nanoparticles and nitrogen-doped carbon, as well as the assembled mesoporous nanowire structure. Finally, a highly stable all-solid-state supercapacitor based on MnCo2O4@NC was demonstrated (1.5% decay after 10,000 cycles).展开更多
Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this app...Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this approach can be used to judge whether the spatial pattern of the objective is regular,random or aggregated in space.The lacunarity analysis,however,cannot afford many quantitative information.Therefore,this study proposed the lacunarity variation index(LVI)to reflect the rates of variation of lacunarity with the resolution.In comparison with lacunarity analysis,the simulated experiments show that the LVI analysis can distinguish the basic spatial pattern of the geography objects more clearly and detect the scale of aggregated data.The experiment showed that different slope types in the Loess Plateau display aggregated patterns,and the characteristic scales of these patterns were detected using the slope pattern in the Loess Plateau as the research data.This study can improve the spatial pattern analysis and scale detecting methods,as well as provide a new method for landscape and vegetation community pattern analyses.Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this approach can be used to judge whether the spatial pattern of the objective is regular,random or aggregated in space.The lacunarity analysis,however,cannot afford many quantitative information.Therefore,this study proposed the lacunarity variation index(LVI)to reflect the rates of variation of lacunarity with the resolution.In comparison with lacunarity analysis,the simulated experiments show that the LVI analysis can distinguish the basic spatial pattern of the geography objects more clearly and detect the scale of aggregated data.The experiment showed that different slope types in the Loess Plateau display aggregated patterns,and the characteristic scales of these patterns were detected using the slope pattern in the Loess Plateau as the research data.This study can improve the spatial pattern analysis and scale detecting methods,as well as provide a new method for landscape and vegetation community pattern analyses.展开更多
基金This work was supported by the National Natural Science Foundation of China(Nos.21667019 and 22066017).
文摘High stability and efficient charge separation are two critical factors to construct high-performance photocatalysts.Here,an efficient strategy was provided to fabricate the nanocomposite of graphitic carbon nitride/ferroferric oxide/reduced graphene oxide(g-C_(3)N_(4)/Fe_(3)O_(4)/RGO).The degradation of rhodamine B(RhB)by g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite followed the pseudofirst-order kinetics.The g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite exhibited excellent stability and magnetically separable performance.It was ascertained that the quantum efficiency and separation efficiency of photoexcited charge carriers of g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite were obviously improved.Particularly,the g-C_(3)N_(4)/Fe_(3)O_(4)/RGO nanocomposite with 3 wt.%RGO presented 100%degradation efficiency under visible light irradiation for 75 min.The remarkable photocatalytic degradation activity is attributed to the synergistic interactions among g-C_(3)N_(4),Fe_(3)O_(4),and RGO,along with the efficient interfacial charge separation.
基金The project is supported by the National Natural Science Foundation of China (Nos. 21275076 and 61328401), Jiangsu Provincial Founds for Distinguished Young Scholars (No. BK20130046), Key University Science Research Project of Jiangsu Province (No. 15KJA430006), Program for New Century Excellent Talents in University (No. NCET-13-0853), QingLan Project, Nantong Key Laboratory of New Materials Industrial Technology, SERC Grant (#102170 0142) from A'STAR Singapore, the scholarship from China Scholarships Council (No. 201508320304).
文摘The development of efficient, low-cost, for water splitting, particularly those stable, non-noble-metal electrocatalysts that can catalyze both the hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode, is a challenge. We have developed a facile method for synthesizing CoSe2 nanoparticles uniformly anchored on carbon fiber paper (CoSe2/CF) via pyrolysis and selenization of in situ grown zeolitic imidazolate framework-67 (ZIF-67). CoSe2/CF shows high and stable catalytic activity in both the HER and OER in alkaline solution. At a low cell potential, i.e., 1.63 V, a water electrolyzer equipped with two CoSe2/CF electrodes gave a water-splitting current of 10 mA.cm-2. At a current of 20 mA-cm-2, it can operate without degradation for 30 h. This study not only offers a cost-effective solution for water splitting but also provides a new strategy for developing various catalytic nanostructures by changing the metal-organic framework precursors.
基金supported by the National Natural Science Foundation of China(No.52173267)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX21_XZ013).
文摘Designing electromagnetic wave absorption(EMWA)materials with wide bandwidth,strong absorption,and light weight is still a great challenge for practical applications.Herein,the novel nitrogen doped carbon(NDC)/MoS_(2) composite with rationally designed composition and structure was developed.The NDC particles were introduced into MoS_(2) nanosheets through the calcination of ZIF-8 precursor and consequent hydrothermal process.A series of characterizations were carried out to investigate the physical properties of the as-prepared nanocomposites.The NDC particles exhibited the shape of rhombic dodecahedron with the size of about 500 nm,which were decorated on flower-shaped MoS_(2) with the size of about 3μm.With the increasing NDC content,the absorbing properties of NDC/MoS_(2) composites increased firstly and then decreased.The features of NDC/MoS_(2) composite including interconnected porous structure,nitrogen dopant,and appropriate electrical conductivity gave rise to the polarization,multiple reflection,multiple scattering,and impedance matching,resulting in the outstanding EMWA performance.With a filler loading ratio of 30 wt.%,the optimized EMWA property can be achieved when the mass ratio of NDC to MoS_(2) was adjusted to be 1:1.At a coating thickness of 3.0 mm,the effective EMWA bandwidth(<−10 dB)reached 6.08 GHz(8.56–14.64 GHz).These satisfactory achievements provide a way for the reasonable design of high-performance EMWA and new ideas for future research on wideband EMWA.
基金financially supported by the National Natural Science Foundation of China(No.52173267)the Open Fund of National&Local Joint Engineering Research Center for Mineral Salt Deep Utilization(No.SF201902)。
文摘A highly efficient absorber with features including lightweight, broad bandwidth, and tunable electromagnetic property still remains challenging for practical applications. Herein, the Porphyra-derived porous carbon(PPC) was fabricated via facile procedures of low-temperature pre-carbonization combined with KOH chemical activation. The composition, microstructure, and electromagnetic wave absorption properties of the samples were elucidated based on X-ray diffraction(XRD), Raman, X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), transmission electron microscopy(TEM),Brunauer-Emmer-Teller(BET), and vector network analyzer(VNA). The porosity of PPC can be readily regulated by adjusting activation temperature. The PPC obtained at 750 ℃ was composed of a threedimensional hierarchically porous carbon network. The C and N elements of natural Porphyra were introduced into the carbon skeleton during the carbonization process. The large specific surface, dopants, and three-dimensional hierarchically porous carbon network can effectively improve the impedance matching and dielectric dissipation, leading to an excellent electromagnetic wave absorption performance. Especially, the optimal reflection loss(RL) value reached –57.75 d B at 9.68 GHz with a broad bandwidth(RL< –10 d B) value of 7.60 GHz at 3.5 mm. Overall, the results indicate that the PPC can provide a new way to achieve lightweight, effective, and sustainable absorbers.
基金The work was supported by the National Natural Science Foundation of China (NSFC) (Nos. 61525402 and 5161101159), Key University Science Research Project of Jiangsu Province (No. 15KJA430006), QingLan Project, National Postdoctoral Program for Innovative Talents (No. BX201600072), China Postdoctoral Science Foundation (No. 2016M601792).
文摘A highly active and stable oxygen evolution reaction (OER) electrocatalyst is critical for hydrogen production from water splitting. Herein, three-dimensional Ni3Sa@graphene@Co9S8 (Ni3S2@G@Co9S8), a sandwich- structured OER electro-catalyst, was grown in situ on nickel foam; it afforded an enhanced catalytic performance when highly conductive graphene is introduced as an intermediary for enhancing the electron transfer rate and stability. Serving as a free-standing electrocatalytic electrode, Ni3S2@G@Co9S8 presents excellent electrocatalytic activities for OER: A low onset overpotential (2 mA·cm^-2 at 174 mV), large anode current density (10 mA·cm^-2 at an overpotential of 210 mV), low Tafel slope (66 mV·dec^-1), and predominant durability of over 96 h (releasing a current density of N 14 mA·cm^-2 with a low and constant overpotential of 215 mV) in a 1 M KOH solution. This work provides a promising, cost-efficient electrocatalyst and sheds new light on improving the electrochemical performance of composites through enhancing the electron transfer rate and stability by introducing graphene as an intermediary.
基金Acknowledgements The project was supported by the National Natural Science Foundation of China (Nos. 61525402 and 21275076), Jiangsu Provincial Funds for Distinguished Young Scholars (No. BK20130046), Program for New Century Excellent Talents in University (No. NCET- 13-0853), QingLan Project, Synergetic Innovation Center for Organic Electronics and Information Displays, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
文摘Triangular Ni(HCO3)2 nanosheets were synthesized via a template-free solvothermal method. The phase transition and formation mechanism were explored systematically. Further investigation indicated that the reaction time and pH have significant effects on the morphology and size distribution of the triangular Ni(HCO3)2 nanosheets. More interestingly, the resulting product had an ultra-thin structure and high specific surface area, which can effectively accelerate the charge transport during charge--discharge processes. As a result, the triangular Ni(HCO3)2 nanosheets not only exhibited high specific capacitance (1,797 F·g^-1 at 5 A·g^-1 and 1,060 F·g^-1 at 50 A·g^-1), but also showed excellent cycling stability with a high current density (-80% capacitance retention after 5,000 cycles at the current density of 20 A·g^-1).
基金Acknowledgements The project is supported by the National Basic Research Program of China (No. 2014CB660808), Jiangsu Provincial Founds for Distinguished Young Scholars (No. BK20130046), the National Natural Science Foundation of China (Nos. 61525402 and 21275076), QingLan Project, Program for New Century Excellent Talents in University (No. NCET-13-0853), Synergetic Innovation Center for Organic Electronics and Information Displays, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), SERC Grant (No. 1021700142) from A*STAR, Singapore, the scholarship from China Scholarships Council (No. 201508320304), the Jiangsu Provincial Founds for Graduate Student Innovation Project (No. KYLX15_0821).
文摘The rational design of earth-abundant catalysts with excellent water splitting activities is important to obtain clean fuels for sustainable energy devices. In this study, mixed transition metal oxide nanoparticles encapsulated in nitrogendoped carbon (denoted as AB2O4@NC) were developed using a one-pot protocol, wherein a metal-organic complex was adopted as the precursor. As a proof of concept, MnCo2O4@NC was used as an electrocatalyst for water oxidation, and demonstrated an outstanding electrocatalytic activity with low overpotential to achieve a current density of 10 mA·cm^-1 0/10 = 287 mV), small Tafel slope (55 mV·dec^-1), and high stability (96% retention after 20 h). The excellent electrochemical performance benefited from the synergistic effects of the MnCo2O4 nanoparticles and nitrogen-doped carbon, as well as the assembled mesoporous nanowire structure. Finally, a highly stable all-solid-state supercapacitor based on MnCo2O4@NC was demonstrated (1.5% decay after 10,000 cycles).
基金supported by the National Natural Science Foundation of China(Grant Nos.41930102,41571383,41771415,41801321,and 41701450).
文摘Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this approach can be used to judge whether the spatial pattern of the objective is regular,random or aggregated in space.The lacunarity analysis,however,cannot afford many quantitative information.Therefore,this study proposed the lacunarity variation index(LVI)to reflect the rates of variation of lacunarity with the resolution.In comparison with lacunarity analysis,the simulated experiments show that the LVI analysis can distinguish the basic spatial pattern of the geography objects more clearly and detect the scale of aggregated data.The experiment showed that different slope types in the Loess Plateau display aggregated patterns,and the characteristic scales of these patterns were detected using the slope pattern in the Loess Plateau as the research data.This study can improve the spatial pattern analysis and scale detecting methods,as well as provide a new method for landscape and vegetation community pattern analyses.Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this approach can be used to judge whether the spatial pattern of the objective is regular,random or aggregated in space.The lacunarity analysis,however,cannot afford many quantitative information.Therefore,this study proposed the lacunarity variation index(LVI)to reflect the rates of variation of lacunarity with the resolution.In comparison with lacunarity analysis,the simulated experiments show that the LVI analysis can distinguish the basic spatial pattern of the geography objects more clearly and detect the scale of aggregated data.The experiment showed that different slope types in the Loess Plateau display aggregated patterns,and the characteristic scales of these patterns were detected using the slope pattern in the Loess Plateau as the research data.This study can improve the spatial pattern analysis and scale detecting methods,as well as provide a new method for landscape and vegetation community pattern analyses.