Hydrogen peroxide(H_(2)O_(2))is extensively used in medical disinfection,water treatment,and environmental protection.To achieve the green synthesis of H_(2)O_(2),g-C_(3)N_(4)-based photocatalysis is an effective stra...Hydrogen peroxide(H_(2)O_(2))is extensively used in medical disinfection,water treatment,and environmental protection.To achieve the green synthesis of H_(2)O_(2),g-C_(3)N_(4)-based photocatalysis is an effective strategy and shows great potential.Nonetheless,single g-C_(3)N_(4)exhibits poor photocatalytic properties due to severe photogenerated charge recombination.To solve this challenge,this work enables F^(−)adsorption on the surface of g-C_(3)N_(4)nanotubes in solution driven by Coulomb forces through pH adjustment and the addition of NH4F.The photocatalytic H_(2)O_(2)production rate of the optimal F^(−)-decorated g-C_(3)N_(4)is three times higher than that of pure g-C_(3)N_(4),attributing to the synergistic effect of F^(−)and H^(+).Quenching experiments verify that the photocatalytic H_(2)O_(2)production process of CNF is a two-electron oxygen reduction process.Electron quenching dynamics of g-C_(3)N_(4)and CNF are revealed by femtosecond transient absorption spectroscopy(fs-TAS).Compared to pure g-C_(3)N_(4),CNF has an additional ultrashort lifetime(3.1 ps)representing the interfacial electron transfer from the conduction band of g-C_(3)N_(4)to F^(−).In situ fs-TAS results show that the interfacial electron transfer rate and electron utilization efficiency are respectively increased from 1.5×10^(8)s^(–1)and 19%in air to 5.0×10^(8)s^(-1)and 45%in O_(2) atmosphere with ethanol sacrificial agent.Hence,the O_(2),H^(+),and photogenerated electrons are key substances in the H_(2)O_(2)evolution.This work has elucidated the dynamics mechanism of enhanced photocatalytic performance of F^(−)-modified g-C_(3)N_(4)and provides inspiration for the design and synthesis of efficient g-C_(3)N_(4)-based photocatalysts.展开更多
A zero-dimensional model which includes 56 species of reactants and 427 reactions is used to study the behavior of charged particles in atmospheric plasmas with different ionization degrees at low altitude （near 0 km...A zero-dimensional model which includes 56 species of reactants and 427 reactions is used to study the behavior of charged particles in atmospheric plasmas with different ionization degrees at low altitude （near 0 km）. The constant coefficient nonlinear equations are solved by using the Quasi-steady-state approximation method. The electron lifetimes are obtained for afterglow plasma with different initial values, and the temporal evolutions of the main charged species are presented, which are dominant in reaction processes. The results show that the electron number density decays quickly. The lifetimes of electrons are shortened by about two orders with increasing ionization degree. Electrons then attach to neutral particles and produce negative ions. When the initial electron densities are in the range of 10l~ ~ 1014 cm-3, the negative ions have sufficiently high densities and long lifetimes for air purification, disinfection and sterilization. Electrons, O（2,-）, O（4,-） CO（4,-） and CO（3,-） are the dominant negative species when the initial electron density neo ≤ 1013 cm^（-3）, and only electrons and CO3 are left when neo 〉 1015 cm^（-3）. N（＋,2）, N＋ and O（＋,2） are dominant in the positive charges for any ionization degree. Other positive species, such as 0（＋,4）, N（＋,3）, NO（＋,2）, NO（＋,2）, Ar（＋,2） and H3O＋. H2O, are dominant only for a certain ionization degree and in a certain period.展开更多
Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h （hereafter called TMF） was then used as scattering layers in the photoano...Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h （hereafter called TMF） was then used as scattering layers in the photoanodes of dye-sensitized solar cells （DSSCs）. The TMF was characterized using scanning electron micro- scopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The TMF had a high surface area of 93.2 m2. g-~ which was beneficial for more dye-loading. Five photoanode films with different internal structures were fabricated by printing different numbers of TMF scattering layers on fluorine-doped tin oxide glass. UV-vis diffuse reflection spectra, incident photon-to-current efficiencies, photocurrent-voltage curves and electrochemical impedance spectroscopy were used to investigate the optical and electrochemical proper- ties of these photoanodes in DSSCs. The presence of nitrogen in the TMF changed the TMF microstructure, which led to a higher open circuit voltage and a longer electron lifetime. In addition, the presence of the nitrogen significantly improved the light utilization and photocur- rent. The highest photoelectric conversion efficiency achieved was 8.08%, which is much higher than that derived from typical P25 nanoparticles （6.52%）.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.U23A20102,52202375,22469001,22261142666,and 22366028)the Natural Science Foundation of Hubei Province of China(No.2022CFA001)。
文摘Hydrogen peroxide(H_(2)O_(2))is extensively used in medical disinfection,water treatment,and environmental protection.To achieve the green synthesis of H_(2)O_(2),g-C_(3)N_(4)-based photocatalysis is an effective strategy and shows great potential.Nonetheless,single g-C_(3)N_(4)exhibits poor photocatalytic properties due to severe photogenerated charge recombination.To solve this challenge,this work enables F^(−)adsorption on the surface of g-C_(3)N_(4)nanotubes in solution driven by Coulomb forces through pH adjustment and the addition of NH4F.The photocatalytic H_(2)O_(2)production rate of the optimal F^(−)-decorated g-C_(3)N_(4)is three times higher than that of pure g-C_(3)N_(4),attributing to the synergistic effect of F^(−)and H^(+).Quenching experiments verify that the photocatalytic H_(2)O_(2)production process of CNF is a two-electron oxygen reduction process.Electron quenching dynamics of g-C_(3)N_(4)and CNF are revealed by femtosecond transient absorption spectroscopy(fs-TAS).Compared to pure g-C_(3)N_(4),CNF has an additional ultrashort lifetime(3.1 ps)representing the interfacial electron transfer from the conduction band of g-C_(3)N_(4)to F^(−).In situ fs-TAS results show that the interfacial electron transfer rate and electron utilization efficiency are respectively increased from 1.5×10^(8)s^(–1)and 19%in air to 5.0×10^(8)s^(-1)and 45%in O_(2) atmosphere with ethanol sacrificial agent.Hence,the O_(2),H^(+),and photogenerated electrons are key substances in the H_(2)O_(2)evolution.This work has elucidated the dynamics mechanism of enhanced photocatalytic performance of F^(−)-modified g-C_(3)N_(4)and provides inspiration for the design and synthesis of efficient g-C_(3)N_(4)-based photocatalysts.
基金supported by the Research Foundation of Education Bureau of Hebei Province,China(No.2009308)National Natural Science Foundation of China(No.10805013)the Natural Science Foundation of Hebei Province(Nos.A2011201132,A2009000149)
文摘A zero-dimensional model which includes 56 species of reactants and 427 reactions is used to study the behavior of charged particles in atmospheric plasmas with different ionization degrees at low altitude （near 0 km）. The constant coefficient nonlinear equations are solved by using the Quasi-steady-state approximation method. The electron lifetimes are obtained for afterglow plasma with different initial values, and the temporal evolutions of the main charged species are presented, which are dominant in reaction processes. The results show that the electron number density decays quickly. The lifetimes of electrons are shortened by about two orders with increasing ionization degree. Electrons then attach to neutral particles and produce negative ions. When the initial electron densities are in the range of 10l~ ~ 1014 cm-3, the negative ions have sufficiently high densities and long lifetimes for air purification, disinfection and sterilization. Electrons, O（2,-）, O（4,-） CO（4,-） and CO（3,-） are the dominant negative species when the initial electron density neo ≤ 1013 cm^（-3）, and only electrons and CO3 are left when neo 〉 1015 cm^（-3）. N（＋,2）, N＋ and O（＋,2） are dominant in the positive charges for any ionization degree. Other positive species, such as 0（＋,4）, N（＋,3）, NO（＋,2）, NO（＋,2）, Ar（＋,2） and H3O＋. H2O, are dominant only for a certain ionization degree and in a certain period.
文摘Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h （hereafter called TMF） was then used as scattering layers in the photoanodes of dye-sensitized solar cells （DSSCs）. The TMF was characterized using scanning electron micro- scopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The TMF had a high surface area of 93.2 m2. g-~ which was beneficial for more dye-loading. Five photoanode films with different internal structures were fabricated by printing different numbers of TMF scattering layers on fluorine-doped tin oxide glass. UV-vis diffuse reflection spectra, incident photon-to-current efficiencies, photocurrent-voltage curves and electrochemical impedance spectroscopy were used to investigate the optical and electrochemical proper- ties of these photoanodes in DSSCs. The presence of nitrogen in the TMF changed the TMF microstructure, which led to a higher open circuit voltage and a longer electron lifetime. In addition, the presence of the nitrogen significantly improved the light utilization and photocur- rent. The highest photoelectric conversion efficiency achieved was 8.08%, which is much higher than that derived from typical P25 nanoparticles （6.52%）.
