Among the synthesis techniques for graphene,chemical vapor deposition(CVD)enables the direct growth of graphene films on insulating substrates.Its advantages include uniform coverage,high quality,scalability,and compa...Among the synthesis techniques for graphene,chemical vapor deposition(CVD)enables the direct growth of graphene films on insulating substrates.Its advantages include uniform coverage,high quality,scalability,and compatibility with industrial processes.Graphene is chemically inert and has a zero-bandgap which poses a problem for its use as a functional layer,and nitrogen doping has become an important way to overcome this.Post-plasma treatment has been explored for the synthesis of nitrogen-doped graphene,but the procedures are intricate and not suitable for large-scale production.We report the direct synthesis of nitrogen-doped graphene on a 4-inch sapphire wafer by ethanol-assisted CVD employing pyridine as the carbon feedstock,where the nitrogen comes from the pyridine and the hydroxyl group in ethanol improves the quality of the graphene produced.Additionally,the types of nitrogen dopant produced and their effects on III-nitride epitaxy were also investigated,resulting in the successful illumination of LED devices.This work presents an effective synthesis strategy for the preparation of nitrogen-doped graphene,and provides a foundation for designing graphene functional layers in optoelectronic devices.展开更多
A red-blood-cell-like nitrogen-doped porous carbon catalyst with a high nitrogen content(9.81%)and specific surface area(631.46 m^2/g)was prepared by using melamine cyanuric acid and glucose as sacrificial template an...A red-blood-cell-like nitrogen-doped porous carbon catalyst with a high nitrogen content(9.81%)and specific surface area(631.46 m^2/g)was prepared by using melamine cyanuric acid and glucose as sacrificial template and carbon source,respectively.This catalyst has a comparable onset potential and a higher diffusion-limiting current density than the commercial 20 wt%Pt/C catalyst in alkaline electrolyte.The oxygen reduction reaction mechanism catalyzed by this catalyst is mainly through a 4e pathway process.The excellent catalytic activity could origin from the synergistic effect of the in-situ doped nitrogen(up to 9.81%)and three-dimensional(3D)porous network structure with high specific surface area,which is conducive to the exposure of more active sites.It is interesting to note that the catalytic activity of oxygen reduction strongly depends on the proportion of graphic N rather than the total N content.展开更多
Aqueous Zn-S batteries have shown great potential in advanced en-ergy storage systems due to their low cost,high theoretical capacity,and in-trinsic safety.However,the slow kinet-ics and low electrical conductivity of...Aqueous Zn-S batteries have shown great potential in advanced en-ergy storage systems due to their low cost,high theoretical capacity,and in-trinsic safety.However,the slow kinet-ics and low electrical conductivity of sul-fur prevent the full use of their capacity,leading to poor cycling performance.We used graphite carbon nitride(g-C_(3)N_(4))as the nitrogen source,and nitrogen-doped Ketjenblack(NKB)was synthesized by solid-phase calcination for use as the sulfur host.Results demonstrate that pyrrolic nitrogen serves as the primary catalytic active site in the sulfur reduction process.The high electronegativity of nitrogen significantly alters the charge distribution of the carbon matrix,changing the electron distribution around sulfur and rendering it electron-rich,which increases the interaction between S and Zn^(2+)and accelerates the reduction kinetics.NKB also forms a three-dimensional cross-linked carbon sphere network,providing abundant defect sites and a large specific surface area,which facilitates electron transfer and improves electrolyte wettability.Combined with the contribution of the ZnI2 additive,the Zn-S battery prepared with the precursor of a g-C_(3)N_(4)∶KB ratio of 3∶4 achieved an ultrahigh discharge capacity of 2069 mAh g^(-1) at a current density of 1 A/g.It also had an excellent rate performance(1257 mAh g^(-1) at 10 A/g)and a long cycling stability(705 mAh g^(-1) after 180 cycles at 5 A/g).This study provides a simple and effective strategy for improving the reduction kinetics of the sulfur cathode in Zn-S batteries and design-ing advanced cathode materials.展开更多
Oxygen reduction reaction(ORR)plays a crucial role in many energy storage and conversion devices.Currently,the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline ...Oxygen reduction reaction(ORR)plays a crucial role in many energy storage and conversion devices.Currently,the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline media still gains a wide attention.In this paper,the mesoporous Fe-N/C catalysts were synthesized through SiO2-mediated templating method using biomass soybeans as the nitrogen and carbon sources.The SiO2 templates create a simultaneous optimization of both the surface functionalities and porous structures of Fe-N/C catalysts.Detailed investigations indicate that the Fe-N/C3 catalyst prepared with the mass ratio of SiO2 to soybean being 3:4 exhibits brilliant electrocatalytic performance,excellent long-term stability and methanol tolerance for the ORR,with the onset potential and the half-wave potential of the ORR being about 0.890 V and 0.783 V(vs RHE),respectively.Meanwhile,the desired 4-electron transfer pathway of the ORR on the catalysts can be observed.It is significantly proposed that the high BET specific surface area and the appropriate pore-size,as well as the high pyridinic-N and total nitrogen loadings may play key roles in enhancing the ORR performance for the Fe-N/C3 catalyst.These results suggest a feasible route based on the economical and sustainable soybean biomass to develop inexpensive and highly efficient non-precious metal electrochemical catalysts for the ORR.展开更多
基金National Natural Science Foundation of China(T2188101)。
文摘Among the synthesis techniques for graphene,chemical vapor deposition(CVD)enables the direct growth of graphene films on insulating substrates.Its advantages include uniform coverage,high quality,scalability,and compatibility with industrial processes.Graphene is chemically inert and has a zero-bandgap which poses a problem for its use as a functional layer,and nitrogen doping has become an important way to overcome this.Post-plasma treatment has been explored for the synthesis of nitrogen-doped graphene,but the procedures are intricate and not suitable for large-scale production.We report the direct synthesis of nitrogen-doped graphene on a 4-inch sapphire wafer by ethanol-assisted CVD employing pyridine as the carbon feedstock,where the nitrogen comes from the pyridine and the hydroxyl group in ethanol improves the quality of the graphene produced.Additionally,the types of nitrogen dopant produced and their effects on III-nitride epitaxy were also investigated,resulting in the successful illumination of LED devices.This work presents an effective synthesis strategy for the preparation of nitrogen-doped graphene,and provides a foundation for designing graphene functional layers in optoelectronic devices.
基金Projects(21571189,21771062)supported by the National Natural Science Foundation of ChinaProjects(2016TP1007,2017TP1001)supported by the Hunan Provincial Science and Technology Plan,China+1 种基金Project(150110005)supported by the Fundamental Research and Innovation Project for Postgraduate of Hunan Province,ChinaProjects(2016CL04,2017CL17)supported by the Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province,China
文摘A red-blood-cell-like nitrogen-doped porous carbon catalyst with a high nitrogen content(9.81%)and specific surface area(631.46 m^2/g)was prepared by using melamine cyanuric acid and glucose as sacrificial template and carbon source,respectively.This catalyst has a comparable onset potential and a higher diffusion-limiting current density than the commercial 20 wt%Pt/C catalyst in alkaline electrolyte.The oxygen reduction reaction mechanism catalyzed by this catalyst is mainly through a 4e pathway process.The excellent catalytic activity could origin from the synergistic effect of the in-situ doped nitrogen(up to 9.81%)and three-dimensional(3D)porous network structure with high specific surface area,which is conducive to the exposure of more active sites.It is interesting to note that the catalytic activity of oxygen reduction strongly depends on the proportion of graphic N rather than the total N content.
文摘Aqueous Zn-S batteries have shown great potential in advanced en-ergy storage systems due to their low cost,high theoretical capacity,and in-trinsic safety.However,the slow kinet-ics and low electrical conductivity of sul-fur prevent the full use of their capacity,leading to poor cycling performance.We used graphite carbon nitride(g-C_(3)N_(4))as the nitrogen source,and nitrogen-doped Ketjenblack(NKB)was synthesized by solid-phase calcination for use as the sulfur host.Results demonstrate that pyrrolic nitrogen serves as the primary catalytic active site in the sulfur reduction process.The high electronegativity of nitrogen significantly alters the charge distribution of the carbon matrix,changing the electron distribution around sulfur and rendering it electron-rich,which increases the interaction between S and Zn^(2+)and accelerates the reduction kinetics.NKB also forms a three-dimensional cross-linked carbon sphere network,providing abundant defect sites and a large specific surface area,which facilitates electron transfer and improves electrolyte wettability.Combined with the contribution of the ZnI2 additive,the Zn-S battery prepared with the precursor of a g-C_(3)N_(4)∶KB ratio of 3∶4 achieved an ultrahigh discharge capacity of 2069 mAh g^(-1) at a current density of 1 A/g.It also had an excellent rate performance(1257 mAh g^(-1) at 10 A/g)and a long cycling stability(705 mAh g^(-1) after 180 cycles at 5 A/g).This study provides a simple and effective strategy for improving the reduction kinetics of the sulfur cathode in Zn-S batteries and design-ing advanced cathode materials.
基金Project(21406273)supported by the National Natural Science Foundation of China
文摘Oxygen reduction reaction(ORR)plays a crucial role in many energy storage and conversion devices.Currently,the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline media still gains a wide attention.In this paper,the mesoporous Fe-N/C catalysts were synthesized through SiO2-mediated templating method using biomass soybeans as the nitrogen and carbon sources.The SiO2 templates create a simultaneous optimization of both the surface functionalities and porous structures of Fe-N/C catalysts.Detailed investigations indicate that the Fe-N/C3 catalyst prepared with the mass ratio of SiO2 to soybean being 3:4 exhibits brilliant electrocatalytic performance,excellent long-term stability and methanol tolerance for the ORR,with the onset potential and the half-wave potential of the ORR being about 0.890 V and 0.783 V(vs RHE),respectively.Meanwhile,the desired 4-electron transfer pathway of the ORR on the catalysts can be observed.It is significantly proposed that the high BET specific surface area and the appropriate pore-size,as well as the high pyridinic-N and total nitrogen loadings may play key roles in enhancing the ORR performance for the Fe-N/C3 catalyst.These results suggest a feasible route based on the economical and sustainable soybean biomass to develop inexpensive and highly efficient non-precious metal electrochemical catalysts for the ORR.
