We report on the preparation of three kinds of Ni nanoparticles supported on carbon （Ni/C） and their application in the catalytic hydrolysis of ammonia borane （AB）. Three Ni/C catalysts were prepared from a Ni met...We report on the preparation of three kinds of Ni nanoparticles supported on carbon （Ni/C） and their application in the catalytic hydrolysis of ammonia borane （AB）. Three Ni/C catalysts were prepared from a Ni metal-organic framework （Ni-MOF） precursor by reduction with KBI-G calcination at 700 ℃ under Ar, and a combination of calcination and reduction, the products being denoted as Ni/C-1, Ni/C-2, and Ni/C-3, respectively. The structure, morphology, specific surface area, and element valence were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, nitrogen adsorption-desorption measurements, and X-ray photoelectron spectra （XPS）. The results demonstrate that Ni/C-1 is composed of amorphous Ni particles agglomerated on carbon, Ni/C-2 is characteristic of crystalline Ni nanoparticles （about 10 nm in size） supported on carbon with Ni oxidized on the surface, while the surface of the Ni particles in Ni/C-3 is less oxidized. The specific surface areas of Ni-MOF, Ni/C-1, Ni/C-2, and Ni/C-3 are 1239, 33, 470, and 451 m2·g-1, respectively. The catalytic hydrolysis of AB with Ni/C-3 shows a hydrogen generation rate of 834 mL-min^-1·g-1 at room temperature and an activation energy of 31.6 kJ/mol. Ni/C-3 shows higher catalytic activity than other materials, which can be attributed to its larger surface area of crystalline Ni. This study offers a promising way to replace noble metal by under ambient conditions. Ni nanoparticles for AB hydrolysis展开更多
Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries.However,the rampant diffusions of soluble lithium polysu...Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries.However,the rampant diffusions of soluble lithium polysulfides (LiPSs) in the electrolyte induced the shuttle effect between anode and cathode,resulting in low sulfur utilization,low energy efficiency and short cycling life.Herein,we prove the rational design and construction of Ni nanoparticles filled in vertically grown N-doped bamboo-like carbon nanotubes (CNTs) on graphene nanosheets (Ni@NG-CNTs) as efficient polysulfide barrier for high-performance LSBs.The unique design integrates graphene nanosheets and CNTs into hierarchical architectures with one-dimensional (1D) CNTs,two-dimensional (2D) ultrethin nanosheets and abundant carbon nanocages.This design provides large surface area for lithium polysulfides (LiPSs) adsorption,accelerates electron transport and enhances electrochemical redox of LiPSs.Benefiting from the unique structural features,the LSBs with the Ni@NG-CNTs as polysulfide barrier keep high reversible specific capacities of 309.1 and 265.0 mAh·g-1 at 5 and 10 C rates after 500 cycles.This work provides a new strategy for constructing self-assembled hybrids of CNTs and graphene nanosheets with abundant carbon nanocages for high-performance LSBs.展开更多
This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam re...This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.展开更多
Carbon nanofibers(CNFs)with high specific surface area show great potential for sodium storage as a hard carbon material.Herein,CNFs anchored with Ni nanoparticles(CNFs/Ni)were prepared through chemical vapor depositi...Carbon nanofibers(CNFs)with high specific surface area show great potential for sodium storage as a hard carbon material.Herein,CNFs anchored with Ni nanoparticles(CNFs/Ni)were prepared through chemical vapor deposition and impregnation reduction methods,in situ growing on the three-dimensional porous copper current collector(3DP-Cu).The coupling effect of high-spin state Ni nanopar-ticles leads to the increase of defect density and the expansion of lattice spacing of CNFs.Meanwhile,the 3DP-Cu ensures a high loading capacity of CNFs and short ion/electron transport channels.As an integral binder-free anode,the 3DP-Cu/CNFs/Ni exhibits excellent electrochemical performance,which demon-strates a high specific capacity with 298.5 mAh g^(-1)at 1000 mA g^(-1)after 1500 cycles,and a high power density with 200 mAh g^(-1)over 1000 cycles at 5000 mA g^(-1).Density functional theory calculation re-sults show that the high-spin state Ni regulates the electronic structure of CNFs,which significantly reduces the adsorption energy for Na^(+)(-2.7 Ev)and thus enables high-rate capability.The regulation of the electronic structure of carbon materials by high-spin state metal provides a new strategy for developing high-power carbonaceous anode materials for sodium-ion batteries.展开更多
Searching for inexpensive,efficient and durable electrocatalysts with earth-abundant elements toward the hydrogen evolution reaction(HER)is of vital importance for the future sustainable hydrogen economy,yet still rem...Searching for inexpensive,efficient and durable electrocatalysts with earth-abundant elements toward the hydrogen evolution reaction(HER)is of vital importance for the future sustainable hydrogen economy,yet still remains a formidable challenge.Herein,a facile template-engaged strategy is demonstrated for the direct in-situ growth of Ni nanoparticles and N-doped carbon nanotubes on carbon nanorod substrates,forming a hierarchically branched architecture(abbreviated as Ni@N-C NT/NRs hereafter).The elaborate construction of such unique hierarchical structure with tightly encapsulated Ni nanoparticles and open configuration endows the as-fabricated Ni@N-C NT/NRs with abundant well-dispersed active sites,enlarged surface area,reduced resistances of charge transfer and mass diffusion,and reinforced mechanical robustness.As a consequence,the optimal Ni@N-C NT/NR catalyst demonstrates superior electrocatalytic activity with relatively low overpotential of 134 mV to deliver a current density of 10 mA·cm^-2 and excellent stability for HER in 0.1 M KOH,holding a great promise for practical scalable H2 production.More importantly,this work offers a reliable methodology for feasible fabrication of robust high-performance carbon-based hierarchical architectures for a variety of electrochemical applications.展开更多
The nanoparticles(NPs)of Ni with different sizes endows its distinctive physical and chemical properties,which represents a typical strategy for the development of high-performance catalysts.However,the size effect of...The nanoparticles(NPs)of Ni with different sizes endows its distinctive physical and chemical properties,which represents a typical strategy for the development of high-performance catalysts.However,the size effect of metallic Ni-NPs on electrocatalytic performance remains ambiguous.Herein,the Ni-NPs with different sizes supported on nitrogen doped carbon(NC)has been synthesized by controlling the pyrolysis temperature,leading to the synthesis of Ni@NC-500(8.3 nm),Ni@NC-280(1.9 nm)and Ni@NC-200(1.0 nm).The electrooxidation of benzyl alcohol(BA)over these nanocatalysts shows the yield of benzoic acid was 99%,82%,55%on Ni@NC-280,Ni@NC-200 and Ni@NC-500,respectively.The experimental and theoretical simulation demonstrate that the difference in the adsorption strength of reactant molecules by Ni-NPs is responsible for their different performance,where the Ni@NC-280 exhibits an optimal adsorption configuration between Ni@NC-280 electrode and BA.This work provides a new angle for designing and synthesizing efficient electrocatalysts,which may be extended to the exploration of various promising electrocatalytic systems.展开更多
文摘We report on the preparation of three kinds of Ni nanoparticles supported on carbon （Ni/C） and their application in the catalytic hydrolysis of ammonia borane （AB）. Three Ni/C catalysts were prepared from a Ni metal-organic framework （Ni-MOF） precursor by reduction with KBI-G calcination at 700 ℃ under Ar, and a combination of calcination and reduction, the products being denoted as Ni/C-1, Ni/C-2, and Ni/C-3, respectively. The structure, morphology, specific surface area, and element valence were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, nitrogen adsorption-desorption measurements, and X-ray photoelectron spectra （XPS）. The results demonstrate that Ni/C-1 is composed of amorphous Ni particles agglomerated on carbon, Ni/C-2 is characteristic of crystalline Ni nanoparticles （about 10 nm in size） supported on carbon with Ni oxidized on the surface, while the surface of the Ni particles in Ni/C-3 is less oxidized. The specific surface areas of Ni-MOF, Ni/C-1, Ni/C-2, and Ni/C-3 are 1239, 33, 470, and 451 m2·g-1, respectively. The catalytic hydrolysis of AB with Ni/C-3 shows a hydrogen generation rate of 834 mL-min^-1·g-1 at room temperature and an activation energy of 31.6 kJ/mol. Ni/C-3 shows higher catalytic activity than other materials, which can be attributed to its larger surface area of crystalline Ni. This study offers a promising way to replace noble metal by under ambient conditions. Ni nanoparticles for AB hydrolysis
基金Postdoctoral Science Foundation of China (No. 2017M611171)National Natural Science Foundation of China (NSFC)(Nos. 21571170, 2150116& and 51702236)Tianjin Municipal Science and Technology Commission (No. 17JCZDJC38000).
文摘Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries.However,the rampant diffusions of soluble lithium polysulfides (LiPSs) in the electrolyte induced the shuttle effect between anode and cathode,resulting in low sulfur utilization,low energy efficiency and short cycling life.Herein,we prove the rational design and construction of Ni nanoparticles filled in vertically grown N-doped bamboo-like carbon nanotubes (CNTs) on graphene nanosheets (Ni@NG-CNTs) as efficient polysulfide barrier for high-performance LSBs.The unique design integrates graphene nanosheets and CNTs into hierarchical architectures with one-dimensional (1D) CNTs,two-dimensional (2D) ultrethin nanosheets and abundant carbon nanocages.This design provides large surface area for lithium polysulfides (LiPSs) adsorption,accelerates electron transport and enhances electrochemical redox of LiPSs.Benefiting from the unique structural features,the LSBs with the Ni@NG-CNTs as polysulfide barrier keep high reversible specific capacities of 309.1 and 265.0 mAh·g-1 at 5 and 10 C rates after 500 cycles.This work provides a new strategy for constructing self-assembled hybrids of CNTs and graphene nanosheets with abundant carbon nanocages for high-performance LSBs.
基金Supported by the National Natural Science Foundation of China(21606008,21436002)the National Basic Research Foundation of China(2013CB733600)the Fundamental Research Funds for the Central Universities(ZY1630,JD1617,buctrc201616,and buctrc201617)
文摘This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.
基金supported by the National Natural Science Foundation of China(Nos.52271011,52102291).
文摘Carbon nanofibers(CNFs)with high specific surface area show great potential for sodium storage as a hard carbon material.Herein,CNFs anchored with Ni nanoparticles(CNFs/Ni)were prepared through chemical vapor deposition and impregnation reduction methods,in situ growing on the three-dimensional porous copper current collector(3DP-Cu).The coupling effect of high-spin state Ni nanopar-ticles leads to the increase of defect density and the expansion of lattice spacing of CNFs.Meanwhile,the 3DP-Cu ensures a high loading capacity of CNFs and short ion/electron transport channels.As an integral binder-free anode,the 3DP-Cu/CNFs/Ni exhibits excellent electrochemical performance,which demon-strates a high specific capacity with 298.5 mAh g^(-1)at 1000 mA g^(-1)after 1500 cycles,and a high power density with 200 mAh g^(-1)over 1000 cycles at 5000 mA g^(-1).Density functional theory calculation re-sults show that the high-spin state Ni regulates the electronic structure of CNFs,which significantly reduces the adsorption energy for Na^(+)(-2.7 Ev)and thus enables high-rate capability.The regulation of the electronic structure of carbon materials by high-spin state metal provides a new strategy for developing high-power carbonaceous anode materials for sodium-ion batteries.
基金The work was financially supported by the National Natural Science Foundation of China(Nos.21972068,21875112,21576139,51871060,51672049)Natural Science Foundation of Jiangsu Province(No.BK20171473).The authors also thank the supports from National and Local Joint Engineering Research Center of Biomedical Functional Materials and a project sponsored by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Searching for inexpensive,efficient and durable electrocatalysts with earth-abundant elements toward the hydrogen evolution reaction(HER)is of vital importance for the future sustainable hydrogen economy,yet still remains a formidable challenge.Herein,a facile template-engaged strategy is demonstrated for the direct in-situ growth of Ni nanoparticles and N-doped carbon nanotubes on carbon nanorod substrates,forming a hierarchically branched architecture(abbreviated as Ni@N-C NT/NRs hereafter).The elaborate construction of such unique hierarchical structure with tightly encapsulated Ni nanoparticles and open configuration endows the as-fabricated Ni@N-C NT/NRs with abundant well-dispersed active sites,enlarged surface area,reduced resistances of charge transfer and mass diffusion,and reinforced mechanical robustness.As a consequence,the optimal Ni@N-C NT/NR catalyst demonstrates superior electrocatalytic activity with relatively low overpotential of 134 mV to deliver a current density of 10 mA·cm^-2 and excellent stability for HER in 0.1 M KOH,holding a great promise for practical scalable H2 production.More importantly,this work offers a reliable methodology for feasible fabrication of robust high-performance carbon-based hierarchical architectures for a variety of electrochemical applications.
基金This work was financially supported by the National Natural Science Foundation of China(No.21771137)the Training Project of Innovation Team of Colleges and Universities in Tianjin(No.TD13-5020)the Natural Science Foundation of Tianjin City(No.18JCJQJC47700).
文摘The nanoparticles(NPs)of Ni with different sizes endows its distinctive physical and chemical properties,which represents a typical strategy for the development of high-performance catalysts.However,the size effect of metallic Ni-NPs on electrocatalytic performance remains ambiguous.Herein,the Ni-NPs with different sizes supported on nitrogen doped carbon(NC)has been synthesized by controlling the pyrolysis temperature,leading to the synthesis of Ni@NC-500(8.3 nm),Ni@NC-280(1.9 nm)and Ni@NC-200(1.0 nm).The electrooxidation of benzyl alcohol(BA)over these nanocatalysts shows the yield of benzoic acid was 99%,82%,55%on Ni@NC-280,Ni@NC-200 and Ni@NC-500,respectively.The experimental and theoretical simulation demonstrate that the difference in the adsorption strength of reactant molecules by Ni-NPs is responsible for their different performance,where the Ni@NC-280 exhibits an optimal adsorption configuration between Ni@NC-280 electrode and BA.This work provides a new angle for designing and synthesizing efficient electrocatalysts,which may be extended to the exploration of various promising electrocatalytic systems.
