Photocatalytic water oxidation is a crucial step in water splitting,but is generally restricted by the slow kinetics.Therefore,it is necessary to develop high-performance water oxidation photocatalysts.Herein,the Fe-d...Photocatalytic water oxidation is a crucial step in water splitting,but is generally restricted by the slow kinetics.Therefore,it is necessary to develop high-performance water oxidation photocatalysts.Herein,the Fe-doped Bi2WO6 nanosheets with oxygen vacancies(OVs)were synthesized for enhanced photocatalytic water oxidation efficiency,showing a synergistic effect between Fe dopants and OVs.When a molar fraction of 2%Fe was doped into the Bi2WO6 nanosheets,the visible-light-driven photocatalytic oxygen evolution rate was increased up to 131.3μmol·h^(-1)·g_(cat)^(-1)under ambient conditions,which was more than 3 times that of pure Bi2WO6 nanosheets.The proper doping concentration of Fe could promote the formation of OVs and at the same time modulate the band structure of catalysts,especially the position of the valence band maximum(VBM),leading to effective visible-light absorption and enhanced oxidizing ability of photogenerated holes.With ameliorated localized electron distribution,fast charge transfer channel emerged between the OVs and adjacent metal atoms,which accelerated the charge carrier transfer and promoted the separation of photoexcited electrons and holes.This work provides feasible approaches for designing efficient two-dimensional semiconductor water oxidation photocatalysts that could utilize visible-light,which will make more use of solar energy.展开更多
The feasibility of producing superheavy nuclei in proton evaporation channels was systematically studied within the dinuclear system(DNS)model.Due to the Z=114 proton-shell,one can synthesize Fl isotopes in proton eva...The feasibility of producing superheavy nuclei in proton evaporation channels was systematically studied within the dinuclear system(DNS)model.Due to the Z=114 proton-shell,one can synthesize Fl isotopes in proton evaporation channels.We only considered the case of evaporating one proton first and then n neutrons in this work,other cases were ignored due to the small cross-section.The production cross sections of unknown isotopes ^(290,291)Fl in ^(38)S+^(255)Es reaction are the highest compared with ^(50)Ti+^(243)Np and ^(54)Cr+^(239)Pa reactions,and the maximum cross sections are 1.1 and 15.1 pb,respectively.^(42)S+^(254)Es is a promising candidate to approach the island of stability as the radioactive beam facilities are upgraded in the future,and the production cross sections of ^(291−294)Fl in that reaction are estimated to be 3.2,6.0,4.0,and 0.1 pb,respectively.展开更多
Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attenti...Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attentions in recent years. This work aimed to further improve the catalytic performance of nickel-based catalyst by the introduction of additives, i.e., MgO and FeO, prepared by impregnation method on the micro-channels made of metal-ceramic complex substrate. The prepared catalysts were tested in the same micro-channel reactor by switching the catalyst plates. The results showed that among the tested catalysts Ni-Mg catalyst had the highest activity, especially under harsh conditions, i.e., at high space velocity and/or low reaction temperature. Moreover, the catalyst activity and selectivity were stable during the 12 h on stream test even when the ratio of steam to carbon （SIC） was as low as 1.0. The addition of MgO promoted the active Ni species to have a good dispersion on the substrate, leading to a better catalytic performance for SMR reaction.展开更多
In this work,we revisited the single-step synthesis of CdE(E=S,Se,and Te)quantum dots(QDs).Powdered CdO and elemental chalcogen were directly used for heating-up synthesis.Firstly,the in situ dissolution of the solid ...In this work,we revisited the single-step synthesis of CdE(E=S,Se,and Te)quantum dots(QDs).Powdered CdO and elemental chalcogen were directly used for heating-up synthesis.Firstly,the in situ dissolution of the solid precursors and related QD formation channels were preliminarily investigated.In general,QDs were generated from homogeneous reactions between dissolved cadmium and chalcogen precursors in bulk solution.We found that,during single-step synthesis,both the dissolution of CdO and selenium proceeded faster than their ex situ dissolution respectively.To explain this result,we proposed the existence of extra surface reaction channels for QD formation.That is,QDs could also be generated via on-surface reactions between the solid precursors and the dissolved counter precursors(as“ligands”).The happening of these extra surface reactions would increase the overall dissolution rate of CdO and selenium.Further,the circulation of oleic acid which is peculiar to such single-step synthesis should also partly account for the accelerated dissolution of CdO.Finally,by comparing with two-step synthesis using pre-dissolved CdO,we presented that such single-step synthesis was reliable in making uniform CdE QDs with good reproducibility.Our work reaffirmed the great potential of this single-step strategy in cost-effective synthesis of monodisperse QDs.Moreover,the ligand-promoted surface reaction channels would be applicable in solution-phase synthesis of metal chalcogenide nanocrystals from solid precursors.展开更多
The influence of the ultra-short pulse wavelength on the populations in the three electronic states of CsI molecule is investigated using the time-dependent wave packet method. The calculated results show that the pop...The influence of the ultra-short pulse wavelength on the populations in the three electronic states of CsI molecule is investigated using the time-dependent wave packet method. The calculated results show that the populations in the two excited states approach to the maxima at the wavelengths of 369 nm and 297 nm, respectively. The photodissociation reaction channels of the CsI molecule can be chosen by controlling the pump pulse wavelength.展开更多
基金This work was financially supported by the National Key R&D Program of China(No.2017YFA0207301)the National Natural Science Foundation of China(Nos.21622107,11621063,U1532265,and 21890750)+1 种基金the Youth Innovation Promotion Association CAS(No.2016392),the Key Research Program of Frontier Sciences(No.QYZDY-SSW-SLH011)the Major Program of Development Foundation of Hefei Center for Physical Science and Technology(No.2017FXZY003).
文摘Photocatalytic water oxidation is a crucial step in water splitting,but is generally restricted by the slow kinetics.Therefore,it is necessary to develop high-performance water oxidation photocatalysts.Herein,the Fe-doped Bi2WO6 nanosheets with oxygen vacancies(OVs)were synthesized for enhanced photocatalytic water oxidation efficiency,showing a synergistic effect between Fe dopants and OVs.When a molar fraction of 2%Fe was doped into the Bi2WO6 nanosheets,the visible-light-driven photocatalytic oxygen evolution rate was increased up to 131.3μmol·h^(-1)·g_(cat)^(-1)under ambient conditions,which was more than 3 times that of pure Bi2WO6 nanosheets.The proper doping concentration of Fe could promote the formation of OVs and at the same time modulate the band structure of catalysts,especially the position of the valence band maximum(VBM),leading to effective visible-light absorption and enhanced oxidizing ability of photogenerated holes.With ameliorated localized electron distribution,fast charge transfer channel emerged between the OVs and adjacent metal atoms,which accelerated the charge carrier transfer and promoted the separation of photoexcited electrons and holes.This work provides feasible approaches for designing efficient two-dimensional semiconductor water oxidation photocatalysts that could utilize visible-light,which will make more use of solar energy.
文摘The feasibility of producing superheavy nuclei in proton evaporation channels was systematically studied within the dinuclear system(DNS)model.Due to the Z=114 proton-shell,one can synthesize Fl isotopes in proton evaporation channels.We only considered the case of evaporating one proton first and then n neutrons in this work,other cases were ignored due to the small cross-section.The production cross sections of unknown isotopes ^(290,291)Fl in ^(38)S+^(255)Es reaction are the highest compared with ^(50)Ti+^(243)Np and ^(54)Cr+^(239)Pa reactions,and the maximum cross sections are 1.1 and 15.1 pb,respectively.^(42)S+^(254)Es is a promising candidate to approach the island of stability as the radioactive beam facilities are upgraded in the future,and the production cross sections of ^(291−294)Fl in that reaction are estimated to be 3.2,6.0,4.0,and 0.1 pb,respectively.
基金supported by the National Natural Science Foundation of China(No.21176137) and Petro China
文摘Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attentions in recent years. This work aimed to further improve the catalytic performance of nickel-based catalyst by the introduction of additives, i.e., MgO and FeO, prepared by impregnation method on the micro-channels made of metal-ceramic complex substrate. The prepared catalysts were tested in the same micro-channel reactor by switching the catalyst plates. The results showed that among the tested catalysts Ni-Mg catalyst had the highest activity, especially under harsh conditions, i.e., at high space velocity and/or low reaction temperature. Moreover, the catalyst activity and selectivity were stable during the 12 h on stream test even when the ratio of steam to carbon （SIC） was as low as 1.0. The addition of MgO promoted the active Ni species to have a good dispersion on the substrate, leading to a better catalytic performance for SMR reaction.
基金by the opening project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(Nos.sklpme2019-4-38 and sklpme2019-4-36)L.X.is grateful to the National Natural Science Foundation of China(NSFC,No.22005205).
文摘In this work,we revisited the single-step synthesis of CdE(E=S,Se,and Te)quantum dots(QDs).Powdered CdO and elemental chalcogen were directly used for heating-up synthesis.Firstly,the in situ dissolution of the solid precursors and related QD formation channels were preliminarily investigated.In general,QDs were generated from homogeneous reactions between dissolved cadmium and chalcogen precursors in bulk solution.We found that,during single-step synthesis,both the dissolution of CdO and selenium proceeded faster than their ex situ dissolution respectively.To explain this result,we proposed the existence of extra surface reaction channels for QD formation.That is,QDs could also be generated via on-surface reactions between the solid precursors and the dissolved counter precursors(as“ligands”).The happening of these extra surface reactions would increase the overall dissolution rate of CdO and selenium.Further,the circulation of oleic acid which is peculiar to such single-step synthesis should also partly account for the accelerated dissolution of CdO.Finally,by comparing with two-step synthesis using pre-dissolved CdO,we presented that such single-step synthesis was reliable in making uniform CdE QDs with good reproducibility.Our work reaffirmed the great potential of this single-step strategy in cost-effective synthesis of monodisperse QDs.Moreover,the ligand-promoted surface reaction channels would be applicable in solution-phase synthesis of metal chalcogenide nanocrystals from solid precursors.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674114 and 10604045)
文摘The influence of the ultra-short pulse wavelength on the populations in the three electronic states of CsI molecule is investigated using the time-dependent wave packet method. The calculated results show that the populations in the two excited states approach to the maxima at the wavelengths of 369 nm and 297 nm, respectively. The photodissociation reaction channels of the CsI molecule can be chosen by controlling the pump pulse wavelength.
