For efficient solar energy conversion,the morphology engineering of hollow graphitic carbon nitride(gC3 N4)is one of the promising approachs benefiting from abundant exposed active sites and short photocarrier transpo...For efficient solar energy conversion,the morphology engineering of hollow graphitic carbon nitride(gC3 N4)is one of the promising approachs benefiting from abundant exposed active sites and short photocarrier transport distances,but is difficult to control on account of easy structural collapse.Herein,a facile supramolecular electrostatic self-assembly strategy has been developed for the first time to fabricate mesoporous thin-walled g-C3N4 microtubes(mtw-CNT)with shell thickness of ca.13 nm.The morphological control of g-C3N4 enhances specific surface area by 12 times,induces stronger optical absorption,widens bandgap by 0.18 e V,improves photocurrent density by 2.5 times,and prolongs lifetimes of charge carriers from bulk to surface,compared with those of bulk g-C3N4.As a consequence,the transformed g-C3N4 exhibits the optimum photocatalytic H2-production rate of 3.99 mmol·h^-1·g^-1(λ>420 nm)with remarkable apparent quantum efficiency of 8.7%(λ=420±15 nm)and long-term stability.Moreover,mtw-CNT also achieves high photocatalytic CO2-to-CO selectivity of 96%(λ>420 nm),much better than those on the most previously reported porous g-C3N4 photocatalysts prepared by the conventional hard-templating and soft-templating methods.展开更多
A template-free hydrothermal-assisted thermal polymerization method has been developed for the large-scale synthesis of one-dimensional （1D） graphitic carbon nitride （g-C3N4） microtubes. The g-C3N4 microtubes were...A template-free hydrothermal-assisted thermal polymerization method has been developed for the large-scale synthesis of one-dimensional （1D） graphitic carbon nitride （g-C3N4） microtubes. The g-C3N4 microtubes were obtained by simple thermal polymerization of melamine-cyanuric acid complex microrods under N2 atmosphere, which were synthesized by hydrothermal treatment of melamine solution at 180℃ for 24 h. The as-obtained g-C3N4 microtubes exhibited a large surface area and a unique one-dimensional tubular structure, which provided abundant active sites for proton reduction and also facilitated the electron transfer processes. As such, the g-C3N4 microtubes showed enhanced photocatalytic H2 production activity in lactic acid aqueous solutions under visible light irradiation （A 〉 420 nm）, which was - 3.1 times higher than that of bulk g-C3N4 prepared by direct thermal polymerization of the melamine precursor under the same calcination conditions.展开更多
Carbon dioxide reacts with porous media while flowing through them enhancing their permeability.Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores,natural cores and micro...Carbon dioxide reacts with porous media while flowing through them enhancing their permeability.Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores,natural cores and microtubes with an inner diameter of 5 μm.The results show that the permeability of H2O-saturated cores(containing carbonate ingredients) was enhanced by increasing the injection volume of a CO2-H2O solution.This enhancement is attributable to carbon dioxide's corrosion,which is justified by SEM scanning.The same phenomenon occurs with a CO2-H2O solution in microtubes,but for a different reason.The gas flow velocity of carbon dioxide in microtubes was approximately 100% faster than that of nitrogen because of the scale and the squeezing effects.Carbon dioxide molecules dissolved in water accelerate the diffusion rate of water molecules within the boundary layer,which in turn diminishes the thickness of the water film and enlarges the effective pore size.This flow behavior facilitates the injection of carbon dioxide into low-permeability reservoirs for oil-displacement and formation energy buildup purposes.This behavior also increases the potential for carbon dioxide channeling or release from the formation.展开更多
基金financially supported by the National Natural Science Foundation of China(21902051)the Natural Science Foundation of Fujian Province(2017J01014 and 2019J05090)the Graphene Power and Composite Research Center of Fujian Province(2017H2001)。
文摘For efficient solar energy conversion,the morphology engineering of hollow graphitic carbon nitride(gC3 N4)is one of the promising approachs benefiting from abundant exposed active sites and short photocarrier transport distances,but is difficult to control on account of easy structural collapse.Herein,a facile supramolecular electrostatic self-assembly strategy has been developed for the first time to fabricate mesoporous thin-walled g-C3N4 microtubes(mtw-CNT)with shell thickness of ca.13 nm.The morphological control of g-C3N4 enhances specific surface area by 12 times,induces stronger optical absorption,widens bandgap by 0.18 e V,improves photocurrent density by 2.5 times,and prolongs lifetimes of charge carriers from bulk to surface,compared with those of bulk g-C3N4.As a consequence,the transformed g-C3N4 exhibits the optimum photocatalytic H2-production rate of 3.99 mmol·h^-1·g^-1(λ>420 nm)with remarkable apparent quantum efficiency of 8.7%(λ=420±15 nm)and long-term stability.Moreover,mtw-CNT also achieves high photocatalytic CO2-to-CO selectivity of 96%(λ>420 nm),much better than those on the most previously reported porous g-C3N4 photocatalysts prepared by the conventional hard-templating and soft-templating methods.
文摘A template-free hydrothermal-assisted thermal polymerization method has been developed for the large-scale synthesis of one-dimensional （1D） graphitic carbon nitride （g-C3N4） microtubes. The g-C3N4 microtubes were obtained by simple thermal polymerization of melamine-cyanuric acid complex microrods under N2 atmosphere, which were synthesized by hydrothermal treatment of melamine solution at 180℃ for 24 h. The as-obtained g-C3N4 microtubes exhibited a large surface area and a unique one-dimensional tubular structure, which provided abundant active sites for proton reduction and also facilitated the electron transfer processes. As such, the g-C3N4 microtubes showed enhanced photocatalytic H2 production activity in lactic acid aqueous solutions under visible light irradiation （A 〉 420 nm）, which was - 3.1 times higher than that of bulk g-C3N4 prepared by direct thermal polymerization of the melamine precursor under the same calcination conditions.
基金the "973" Project from the Ministry of Science and Technology of China (Grant No.2006CB705805)the National Key Technology R&D Program (Grant Nos.2006BAB03B06 & 2007BAB17B0B)
文摘Carbon dioxide reacts with porous media while flowing through them enhancing their permeability.Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores,natural cores and microtubes with an inner diameter of 5 μm.The results show that the permeability of H2O-saturated cores(containing carbonate ingredients) was enhanced by increasing the injection volume of a CO2-H2O solution.This enhancement is attributable to carbon dioxide's corrosion,which is justified by SEM scanning.The same phenomenon occurs with a CO2-H2O solution in microtubes,but for a different reason.The gas flow velocity of carbon dioxide in microtubes was approximately 100% faster than that of nitrogen because of the scale and the squeezing effects.Carbon dioxide molecules dissolved in water accelerate the diffusion rate of water molecules within the boundary layer,which in turn diminishes the thickness of the water film and enlarges the effective pore size.This flow behavior facilitates the injection of carbon dioxide into low-permeability reservoirs for oil-displacement and formation energy buildup purposes.This behavior also increases the potential for carbon dioxide channeling or release from the formation.
