The vapor deposition chemical reaction processes, which are of extremely extensive applications, can be classified as a mathematical model by the following governing nonlinear partial differential equations containing...The vapor deposition chemical reaction processes, which are of extremely extensive applications, can be classified as a mathematical model by the following governing nonlinear partial differential equations containing velocity vector, temperature field, pressure field, and gas mass field. The mixed finite element (MFE) method is employed to study the system of equations for the vapor deposition chemical reaction processes. The semidiscrete and fully discrete MFE formulations are derived. And the existence and convergence (error estimate) of the semidiscrete and fully discrete MFE solutions are demonstrated. By employing MFE method to treat the system of equations for the vapor deposition chemical reaction processes, the numerical solutions of the velocity vector, the temperature field, the pressure field, and the gas mass field can be found out simultaneously. Thus, these researches are not only of important theoretical means, but also of extremely extensive applied vistas.展开更多
The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,mo...The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme(SNG). In contrast with routine N-doped graphene framework(NGF) with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^(-1), a large surface area of 1531 m^2 g^(-1), a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.展开更多
RuO2 nanoparticles supported on multi-walled carbon nanotubes(CNTs) functionalized with oxygen(OCNTs) and nitrogen(NCNTs) were employed for the oxygen evolution reaction(OER) in 0.1 M KOH.The catalysts were sy...RuO2 nanoparticles supported on multi-walled carbon nanotubes(CNTs) functionalized with oxygen(OCNTs) and nitrogen(NCNTs) were employed for the oxygen evolution reaction(OER) in 0.1 M KOH.The catalysts were synthesized by metal-organic chemical vapor deposition using ruthenium carbonyl(Ru3(CO)(12)) as Ru precursor. The obtained RuO2/OCNT and RuO2/NCNT composites were characterized using TEM, H2-TPR, XRD and XPS in order probe structure–activity correlations, particularly, the effect of the different surface functional groups on the electrochemical OER performance. The electrocatalytic activity and stability of the catalysts with mean RuO2 particle sizes of 13–14 nm was evaluated by linear sweep voltammetry, cyclic voltammetry, and chronopotentiometry, showing that the generation of nitrogen-containing functional groups on CNTs was beneficial for both OER activity and stability. In the presence of RuO2, carbon corrosion was found to be significantly less severe.展开更多
The aim of this paper was to test the thermal and environmental stability of poly(4-ethynyl-p-xylylene- co-p-xylylene) thin films prepared by chemical vapor deposition (CVD) and to optimize the reaction conditions...The aim of this paper was to test the thermal and environmental stability of poly(4-ethynyl-p-xylylene- co-p-xylylene) thin films prepared by chemical vapor deposition (CVD) and to optimize the reaction conditions of the polymer. Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and fluorescence microscopy were employed to investigate the stability of the reactive polymer coatings in various environmental conditions. Chemical reactivity of the thin films were then tested by Huisgen 1,3-dipolar cycloaddition reaction ("click" reaction). The alkyne functional groups on poly(4- ethynyl-p-xylylene-co-p-xylylene) thin films were found to be stable under ambient storage conditions and thermally stable up to 100 ℃ when annealed at 0.08 Torr in argon. We also optimized the click reaction conditions of azide-functionalized molecules with poly(4-ethynyl-p-xylylene-co-p-xylylene). The best reaction result was achieved, when copper concentration was 0.5 retool/L, sodium ascorbate concentration to copper concentration was 5:1. In contrast, the azide concentration and temperature had no obvious effect on the surface reaction.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos.10471100 and 40437017)the Science and Technology Foundation of Beijing Jiaotong University
文摘The vapor deposition chemical reaction processes, which are of extremely extensive applications, can be classified as a mathematical model by the following governing nonlinear partial differential equations containing velocity vector, temperature field, pressure field, and gas mass field. The mixed finite element (MFE) method is employed to study the system of equations for the vapor deposition chemical reaction processes. The semidiscrete and fully discrete MFE formulations are derived. And the existence and convergence (error estimate) of the semidiscrete and fully discrete MFE solutions are demonstrated. By employing MFE method to treat the system of equations for the vapor deposition chemical reaction processes, the numerical solutions of the velocity vector, the temperature field, the pressure field, and the gas mass field can be found out simultaneously. Thus, these researches are not only of important theoretical means, but also of extremely extensive applied vistas.
基金supported by the National Key Research and Development Program(2016YFA0202500 and 2016YFA0200102)the Natural Scientific Foundation of China(21776019)
文摘The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme(SNG). In contrast with routine N-doped graphene framework(NGF) with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^(-1), a large surface area of 1531 m^2 g^(-1), a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.
基金the IMPRS-Sur Mat of the Max Planck Society for a research grant
文摘RuO2 nanoparticles supported on multi-walled carbon nanotubes(CNTs) functionalized with oxygen(OCNTs) and nitrogen(NCNTs) were employed for the oxygen evolution reaction(OER) in 0.1 M KOH.The catalysts were synthesized by metal-organic chemical vapor deposition using ruthenium carbonyl(Ru3(CO)(12)) as Ru precursor. The obtained RuO2/OCNT and RuO2/NCNT composites were characterized using TEM, H2-TPR, XRD and XPS in order probe structure–activity correlations, particularly, the effect of the different surface functional groups on the electrochemical OER performance. The electrocatalytic activity and stability of the catalysts with mean RuO2 particle sizes of 13–14 nm was evaluated by linear sweep voltammetry, cyclic voltammetry, and chronopotentiometry, showing that the generation of nitrogen-containing functional groups on CNTs was beneficial for both OER activity and stability. In the presence of RuO2, carbon corrosion was found to be significantly less severe.
基金support from DTRA,under project HDTRA112-1-0039the Army Research Office (ARO) under Grant W911NF-11-1-0251support from the China Scholarship Council (CSC)
文摘The aim of this paper was to test the thermal and environmental stability of poly(4-ethynyl-p-xylylene- co-p-xylylene) thin films prepared by chemical vapor deposition (CVD) and to optimize the reaction conditions of the polymer. Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and fluorescence microscopy were employed to investigate the stability of the reactive polymer coatings in various environmental conditions. Chemical reactivity of the thin films were then tested by Huisgen 1,3-dipolar cycloaddition reaction ("click" reaction). The alkyne functional groups on poly(4- ethynyl-p-xylylene-co-p-xylylene) thin films were found to be stable under ambient storage conditions and thermally stable up to 100 ℃ when annealed at 0.08 Torr in argon. We also optimized the click reaction conditions of azide-functionalized molecules with poly(4-ethynyl-p-xylylene-co-p-xylylene). The best reaction result was achieved, when copper concentration was 0.5 retool/L, sodium ascorbate concentration to copper concentration was 5:1. In contrast, the azide concentration and temperature had no obvious effect on the surface reaction.