Stable silver nanoparticles were synthesized using polyvinyl alcohol （PVA） as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer m...Stable silver nanoparticles were synthesized using polyvinyl alcohol （PVA） as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer matrix. The successful incorporation of silver nanoparticles in a PVA matrix was confirmed by UV–Visible spectroscopy, transmission electron microscopy （TEM） and Fourier transform infrared （FT-IR） spectroscopy. The synthesized silver nanoparticles were characterized by a peak at 426 nm in the UV–Vis spectrum. TEM studies showed the formation of spherical shaped silver nanoparticles of 10-13 nm, following the reduction by UV irradiation. Catalytic properties were studied by means of UV-Visible spectroscopic analysis. The synthesized silver nanoparticles exhibited good catalytic properties in the reduction of methylene blue.展开更多
Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as...Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia synthesis.Graphite and graphitic carbons are of interest as supports for the nanocatalysts.Despite considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood.Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom resolution.By recording snapshots of the reaction dynamics,the behaviour of the catalysts is imaged.The images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support function.These all play key roles in the mobility,sintering and growth of the catalysts.The experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts.展开更多
Efficient removal of formaldehyde from indoor environments is of significance for human health.In this work,a typical binary transition metal oxide that could provide various oxidation states,β-NiMoO4,was employed as...Efficient removal of formaldehyde from indoor environments is of significance for human health.In this work,a typical binary transition metal oxide that could provide various oxidation states,β-NiMoO4,was employed as a support to immobilize the active Pt component(Pt/NiMoO4)for catalytic formaldehyde elimination at low ambient temperature(15℃).The results showed that the hydrothermal preparation temperature and time had a noticeable impact on the morphology and catalytic activity of the samples.The catalyst prepared with hydrothermal temperature of 150℃for 4 hr(Pt-150-4)exhibited superior catalytic activity and stability mainly due to its distinctly porous structure,relative abundance of adsorbed surface hydroxyls/water,and high oxidation ability,which resulted from the interaction of Pt with Ni and Mo of the bimetallic NiMoO4 support.Our results might shed light on the rational design of multifunctional catalysts for removal of indoor air pollutants at low ambient temperature.展开更多
New sustainable syntheses based on solid-state strategies have sparked enormous attention and provided novel routes for the synthesis of supported metallic alloy nanocatalysts(SMACs).Despite considerable recent progre...New sustainable syntheses based on solid-state strategies have sparked enormous attention and provided novel routes for the synthesis of supported metallic alloy nanocatalysts(SMACs).Despite considerable recent progress in this field,most of the developed methods suffer from either complex operations or poorly controlled morphology,which seriously limits their practical applications.Here,we have developed a sustainable strategy for the synthesis of PdAg alloy nanoparticles(NPs)with an ultrafine size and good dispersion on various carbon matrices by directly grinding the precursors in an agate mortar at room temperature.Interestingly,no solvents or organic reagents are used in the synthesis procedure.This simple and green synthesis procedure provides alloy NPs with clean surfaces and thus an abundance of accessible active sites.Based on the combination of this property and the synergistic and alloy effects between Pd and Ag atoms,which endow the NPs with high intrinsic activity,the PdAg/C samples exhibit excellent activities as electrocatalysts for both the hydrogen oxidation and evolution reactions(HOR and HER)in a basic medium.Pd9Ag1/C showed the highest activity in the HOR with the largest j0,m value of 26.5 A g Pd^–1 and j0,s value of 0.033 mA cmPd^–2,as well as in the HER,with the lowest overpotential of 68 mV at 10 mA cm^–2.As this synthetic method can be easily adapted to other systems,the present scalable solid-state strategy may open opportunity for the general synthesis of a wide range of well-defined SMACs for diverse applications.展开更多
Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carri...Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.展开更多
Supported nanoparticles have attracted considerable attention as a promising catalyst for achieving unique properties in numerous applications,including fuel cells,chemical conversion,and batteries.Nanocatalysts demon...Supported nanoparticles have attracted considerable attention as a promising catalyst for achieving unique properties in numerous applications,including fuel cells,chemical conversion,and batteries.Nanocatalysts demonstrate high activity by expanding the number of active sites,but they also intensify deactivation issues,such as agglomeration and poisoning,simultaneously.Exsolution for bottomup synthesis of supported nanoparticles has emerged as a breakthrough technique to overcome limitations associated with conventional nanomaterials.Nanoparticles are uniformly exsolved from perovskite oxide supports and socketed into the oxide support by a one-step reduction process.Their uniformity and stability,resulting from the socketed structure,play a crucial role in the development of novel nanocatalysts.Recently,tremendous research efforts have been dedicated to further controlling exsolution particles.To effectively address exsolution at a more precise level,understanding the underlying mechanism is essential.This review presents a comprehensive overview of the exsolution mechanism,with a focus on its driving force,processes,properties,and synergetic strategies,as well as new pathways for optimizing nanocatalysts in diverse applications.展开更多
Catalytic performance of supported metal catalysts not only depends on the reactivity of metal,but also the adsorption and diffusion properties of gas molecules which are usually affected by many factors,such as tempe...Catalytic performance of supported metal catalysts not only depends on the reactivity of metal,but also the adsorption and diffusion properties of gas molecules which are usually affected by many factors,such as temperature,pressure,properties of metal clusters and substrates,etc.To explore the impact of each of these macroscopic factors,we simulated the movement of CO molecules confined in graphene nanoslits with or without supported Pt nanoparticles.The results of molecular dynamics simulations show that the diffusion of gas molecules is accelerated with high temperature,low pressure or low surface-atom number of supported metals.Notably,the supported metal nanoparticles greatly affect the gas diffusion due to the adsorption of gas molecules.Furthermore,to bridge a quantitative relationship between microscopic simulation and macroscopic properties,a generalized formula is derived from the simulation data to calculate the diffusion coefficient.This work helps to advise the diffusion modulation of gas molecules via structural design of catalysts and regulation of reaction conditions.展开更多
We report herein an innovative design and synthesis of a novel multifunctional nanocatalyst for the transfer hydrogenation(TH)of nitroarenes and olefins using water as a hydrogen source and solvent.The presented nanoc...We report herein an innovative design and synthesis of a novel multifunctional nanocatalyst for the transfer hydrogenation(TH)of nitroarenes and olefins using water as a hydrogen source and solvent.The presented nanocatalyst is composed of NiPd alloy nanoparticles(NPs)supported on reduced graphene oxide(rGO)decorated with metallic Al NPs(Al-rGO/NiPd).In the catalyst,metallic Al NPs serve as the sacrificing agent for hydrogen generation via the Al-H_(2)O reaction,NiPd NPs act as the catalyst for the transfer of the generated hydrogen to the unsaturated compounds,and rGO functions as both a support material and stabilizer for the NPs.Among all tested catalysts,Al-rGO/Ni_(40)Pd_(60)nanocatalysts are found to be the most efficient and selective catalysts in the presented TH of nitroarenes(14 examples)and olefins(14 examples)with yields reaching up to 99%under the optimized reaction conditions.Additionally,Al-rGO/Ni_(40)Pd_(60)nanocatalysts are recyclable catalysts in the TH reactions by catalyzing ten consecutive runs in the TH of nitrobenzene without a significant drop in their initial catalytic activity,which is the first example in this regard.Last but not least,the current transfer hydrogenation protocol provides selectivity for the reduction of only the-NO_(2)group of nitroarenes bearing iodo or bromo substituents on the same aromatic ring.This study is the first example of a TH protocol that employs an Al-modified nanomaterial serving as both a hydrogen generator and reusable catalyst in water without using any additional hydrogen source.展开更多
A facile and green approach has been developed for fabricating well-dispersed palladium nanoparticles(Pd NPs)supported on the surface of poly(N-vinylpyrrolidone)(PVP)-stabilized polystyrene(PS)microspheres.The strateg...A facile and green approach has been developed for fabricating well-dispersed palladium nanoparticles(Pd NPs)supported on the surface of poly(N-vinylpyrrolidone)(PVP)-stabilized polystyrene(PS)microspheres.The strategy harnesses the reducing ability of PVP and the affinity between PVP and Pd NPs to achieve in situ surface-assisted growth of small noble metal NPs on the PS microspheres,without involving any additional stabilizer or reducing agent.The stabilizer-free formation contributes to the superior availability and accessibility of active sites for catalysis.The resulting PS/Pd composite particles have demonstrated excellent catalytic performance in the probe reaction of 4-nitrophenol reduction.As far as we know,this approach has been the first straightforward in situ deposition of Pd NPs on the PS microspheres,obviating surface treatment and the use of an exogenous reducing agent or a stabilizer.Furthermore,it is extendable to the fabrication of other composite systems,PS/Ag composite particles for example.展开更多
The efficient preparation of non-precious metal nanocatalysts embedded in carbon nano/microtubes remains a considerable challenge.Herein,we report a facile self-template and carbonization strategy to fabricate nickel ...The efficient preparation of non-precious metal nanocatalysts embedded in carbon nano/microtubes remains a considerable challenge.Herein,we report a facile self-template and carbonization strategy to fabricate nickel nanoparticle(NP)supporting N-doped carbon microtubes.Firstly,molybdenum trioxide(a-MoO_(3))microrods are coated with polypyrrole(MoO_(3)@PPy)by a simple in situ polymerization route.Then,PPy@PDA-Ni^(2+)microtubes with a hollow structure are obtained by further coating the PDA-Ni^(2+)complex in ammonia solution.In contrast,the direct coating of MoO_(3) microrods with PDA-Ni^(2+)under the same experimental conditions only leads to aggregated PDA-Ni^(2+)spheres.Moreover,nickel/N-doped carbon microtubes(Ni/NCMTs)can be obtained by a further heating treatment and highly graphitic carbon microtubes are achieved by etching the nickel nanoparticles.The hollow Ni/NCMTs exhibit excellent reduction activity on 4-nitrophenol(4-NP).Moreover,the size of Ni nanoparticles(Ni NPs)which can effectively control the catalytic performance of the as-prepared nanocomposites is facilely adjusted via changing the roasting temperature.Benefitting from the highly exposed surface,short diffusion distance,and homogeneous Ni NP dispersion,the Ni/NCMT catalyst exhibits an improved activity on 4-NP.This novel structure is helpful for further applications in hydrogen evolution reaction,supercapacitors and batteries.展开更多
Ammonia borane(AB),with a potential storage capacity of 19.6 wt%H_(2),is an excellent material for chemical storage of hydrogen.However,the use of noble metal catalysts severely hinders the practical application of AB...Ammonia borane(AB),with a potential storage capacity of 19.6 wt%H_(2),is an excellent material for chemical storage of hydrogen.However,the use of noble metal catalysts severely hinders the practical application of AB decomposition for hydrogen generation.In this work,well dispersed CuCo and CoO nanoparticles(CuCo(O))supported on carbon–nitrogen frameworks(CN)have been synthesized through a facile thermal reduction of the Cu-doped ZIF67 precursor.Upon reduction,Co and Cu in the ZIF framework are partially reduced into CuCo particles of about 30 nm,and these active species are anchored on porous carbon–nitrogen matrix inherited ZIF frameworks(denoted as CuCo(O)@CN).The as-prepared material demonstrates a ZIF-67-like polyhedral morphology,good nanoparticle spatial distribution and better active site availability.When used as an AB hydrolysis catalyst,CuCo(O)@CN exhibits excellent catalytic activity,with the highest catalytic efficiency up to 4524 mL min^(−1)g^(−1)and a total turnover frequency(TOF)of 12.4 mol H_(2)per min per molcat,which are among the best performances of noble metal-free catalysts.In addition,the corresponding activation energy is estimated to be as low as 33.8 kJ mol^(−1).Detailed analysis suggests that excllent catalytic performance could be attributed to the synergy between Co and Cu as well as the nitrogen-rich carbon support.展开更多
文摘Stable silver nanoparticles were synthesized using polyvinyl alcohol （PVA） as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer matrix. The successful incorporation of silver nanoparticles in a PVA matrix was confirmed by UV–Visible spectroscopy, transmission electron microscopy （TEM） and Fourier transform infrared （FT-IR） spectroscopy. The synthesized silver nanoparticles were characterized by a peak at 426 nm in the UV–Vis spectrum. TEM studies showed the formation of spherical shaped silver nanoparticles of 10-13 nm, following the reduction by UV irradiation. Catalytic properties were studied by means of UV-Visible spectroscopic analysis. The synthesized silver nanoparticles exhibited good catalytic properties in the reduction of methylene blue.
基金the Engineering and Physical Science Research Council(EPSRC),U.K.for the award of a research grant EP/J0118058/1 and postdoctoral research assistantships(PDRAs) to M.R.W.and R.W.M.from the grant。
文摘Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia synthesis.Graphite and graphitic carbons are of interest as supports for the nanocatalysts.Despite considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood.Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom resolution.By recording snapshots of the reaction dynamics,the behaviour of the catalysts is imaged.The images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support function.These all play key roles in the mobility,sintering and growth of the catalysts.The experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts.
基金supported by the National Natural Science Foundation of China(Nos.21577046 and 21871111)Wuhan Morning Light plan of Youth Science and Technology(No.2017050304010327)
文摘Efficient removal of formaldehyde from indoor environments is of significance for human health.In this work,a typical binary transition metal oxide that could provide various oxidation states,β-NiMoO4,was employed as a support to immobilize the active Pt component(Pt/NiMoO4)for catalytic formaldehyde elimination at low ambient temperature(15℃).The results showed that the hydrothermal preparation temperature and time had a noticeable impact on the morphology and catalytic activity of the samples.The catalyst prepared with hydrothermal temperature of 150℃for 4 hr(Pt-150-4)exhibited superior catalytic activity and stability mainly due to its distinctly porous structure,relative abundance of adsorbed surface hydroxyls/water,and high oxidation ability,which resulted from the interaction of Pt with Ni and Mo of the bimetallic NiMoO4 support.Our results might shed light on the rational design of multifunctional catalysts for removal of indoor air pollutants at low ambient temperature.
文摘New sustainable syntheses based on solid-state strategies have sparked enormous attention and provided novel routes for the synthesis of supported metallic alloy nanocatalysts(SMACs).Despite considerable recent progress in this field,most of the developed methods suffer from either complex operations or poorly controlled morphology,which seriously limits their practical applications.Here,we have developed a sustainable strategy for the synthesis of PdAg alloy nanoparticles(NPs)with an ultrafine size and good dispersion on various carbon matrices by directly grinding the precursors in an agate mortar at room temperature.Interestingly,no solvents or organic reagents are used in the synthesis procedure.This simple and green synthesis procedure provides alloy NPs with clean surfaces and thus an abundance of accessible active sites.Based on the combination of this property and the synergistic and alloy effects between Pd and Ag atoms,which endow the NPs with high intrinsic activity,the PdAg/C samples exhibit excellent activities as electrocatalysts for both the hydrogen oxidation and evolution reactions(HOR and HER)in a basic medium.Pd9Ag1/C showed the highest activity in the HOR with the largest j0,m value of 26.5 A g Pd^–1 and j0,s value of 0.033 mA cmPd^–2,as well as in the HER,with the lowest overpotential of 68 mV at 10 mA cm^–2.As this synthetic method can be easily adapted to other systems,the present scalable solid-state strategy may open opportunity for the general synthesis of a wide range of well-defined SMACs for diverse applications.
基金E.L.,K.L.,P.W.,and S.T.are supported by the SCCER-Heat and Energy Storage program
文摘Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.
基金This study was supported by the National Research Foundation of Korea(NRF-2021R1C1C1010233)funded by the Korean government(MSIT)+1 种基金This research was also supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)Grant(No.G032542411)funded by the Korea Ministry of Trade,Industry,and Energy(MOTIE).
文摘Supported nanoparticles have attracted considerable attention as a promising catalyst for achieving unique properties in numerous applications,including fuel cells,chemical conversion,and batteries.Nanocatalysts demonstrate high activity by expanding the number of active sites,but they also intensify deactivation issues,such as agglomeration and poisoning,simultaneously.Exsolution for bottomup synthesis of supported nanoparticles has emerged as a breakthrough technique to overcome limitations associated with conventional nanomaterials.Nanoparticles are uniformly exsolved from perovskite oxide supports and socketed into the oxide support by a one-step reduction process.Their uniformity and stability,resulting from the socketed structure,play a crucial role in the development of novel nanocatalysts.Recently,tremendous research efforts have been dedicated to further controlling exsolution particles.To effectively address exsolution at a more precise level,understanding the underlying mechanism is essential.This review presents a comprehensive overview of the exsolution mechanism,with a focus on its driving force,processes,properties,and synergetic strategies,as well as new pathways for optimizing nanocatalysts in diverse applications.
基金the financial support from the National Natural Science Foundation of China(NSFC-21625604,21878272,91934302 and 21706229)。
文摘Catalytic performance of supported metal catalysts not only depends on the reactivity of metal,but also the adsorption and diffusion properties of gas molecules which are usually affected by many factors,such as temperature,pressure,properties of metal clusters and substrates,etc.To explore the impact of each of these macroscopic factors,we simulated the movement of CO molecules confined in graphene nanoslits with or without supported Pt nanoparticles.The results of molecular dynamics simulations show that the diffusion of gas molecules is accelerated with high temperature,low pressure or low surface-atom number of supported metals.Notably,the supported metal nanoparticles greatly affect the gas diffusion due to the adsorption of gas molecules.Furthermore,to bridge a quantitative relationship between microscopic simulation and macroscopic properties,a generalized formula is derived from the simulation data to calculate the diffusion coefficient.This work helps to advise the diffusion modulation of gas molecules via structural design of catalysts and regulation of reaction conditions.
基金Scientific and Technological Research Council of Turkey(TUBITAK)(Grant No:118Z577)。
文摘We report herein an innovative design and synthesis of a novel multifunctional nanocatalyst for the transfer hydrogenation(TH)of nitroarenes and olefins using water as a hydrogen source and solvent.The presented nanocatalyst is composed of NiPd alloy nanoparticles(NPs)supported on reduced graphene oxide(rGO)decorated with metallic Al NPs(Al-rGO/NiPd).In the catalyst,metallic Al NPs serve as the sacrificing agent for hydrogen generation via the Al-H_(2)O reaction,NiPd NPs act as the catalyst for the transfer of the generated hydrogen to the unsaturated compounds,and rGO functions as both a support material and stabilizer for the NPs.Among all tested catalysts,Al-rGO/Ni_(40)Pd_(60)nanocatalysts are found to be the most efficient and selective catalysts in the presented TH of nitroarenes(14 examples)and olefins(14 examples)with yields reaching up to 99%under the optimized reaction conditions.Additionally,Al-rGO/Ni_(40)Pd_(60)nanocatalysts are recyclable catalysts in the TH reactions by catalyzing ten consecutive runs in the TH of nitrobenzene without a significant drop in their initial catalytic activity,which is the first example in this regard.Last but not least,the current transfer hydrogenation protocol provides selectivity for the reduction of only the-NO_(2)group of nitroarenes bearing iodo or bromo substituents on the same aromatic ring.This study is the first example of a TH protocol that employs an Al-modified nanomaterial serving as both a hydrogen generator and reusable catalyst in water without using any additional hydrogen source.
基金National Natural Science Foundation of China(no.21204030)the MOE&the SAFEA for the 111 Project(B13025)for financial support.
文摘A facile and green approach has been developed for fabricating well-dispersed palladium nanoparticles(Pd NPs)supported on the surface of poly(N-vinylpyrrolidone)(PVP)-stabilized polystyrene(PS)microspheres.The strategy harnesses the reducing ability of PVP and the affinity between PVP and Pd NPs to achieve in situ surface-assisted growth of small noble metal NPs on the PS microspheres,without involving any additional stabilizer or reducing agent.The stabilizer-free formation contributes to the superior availability and accessibility of active sites for catalysis.The resulting PS/Pd composite particles have demonstrated excellent catalytic performance in the probe reaction of 4-nitrophenol reduction.As far as we know,this approach has been the first straightforward in situ deposition of Pd NPs on the PS microspheres,obviating surface treatment and the use of an exogenous reducing agent or a stabilizer.Furthermore,it is extendable to the fabrication of other composite systems,PS/Ag composite particles for example.
基金the financial support provided by the National Natural Science Foundation of China(No.21305086 and 21371108)the Research Innovation Program of Shanghai Municipal Education Commission(14YZ138)+1 种基金the Special for Outstanding Young Teachers for Outstanding Young Teachers in Shanghai Higher Education Institutions(ZZGJD13016)the Start-up Funding of Shanghai University of Engineering and Science(2013td08).
文摘The efficient preparation of non-precious metal nanocatalysts embedded in carbon nano/microtubes remains a considerable challenge.Herein,we report a facile self-template and carbonization strategy to fabricate nickel nanoparticle(NP)supporting N-doped carbon microtubes.Firstly,molybdenum trioxide(a-MoO_(3))microrods are coated with polypyrrole(MoO_(3)@PPy)by a simple in situ polymerization route.Then,PPy@PDA-Ni^(2+)microtubes with a hollow structure are obtained by further coating the PDA-Ni^(2+)complex in ammonia solution.In contrast,the direct coating of MoO_(3) microrods with PDA-Ni^(2+)under the same experimental conditions only leads to aggregated PDA-Ni^(2+)spheres.Moreover,nickel/N-doped carbon microtubes(Ni/NCMTs)can be obtained by a further heating treatment and highly graphitic carbon microtubes are achieved by etching the nickel nanoparticles.The hollow Ni/NCMTs exhibit excellent reduction activity on 4-nitrophenol(4-NP).Moreover,the size of Ni nanoparticles(Ni NPs)which can effectively control the catalytic performance of the as-prepared nanocomposites is facilely adjusted via changing the roasting temperature.Benefitting from the highly exposed surface,short diffusion distance,and homogeneous Ni NP dispersion,the Ni/NCMT catalyst exhibits an improved activity on 4-NP.This novel structure is helpful for further applications in hydrogen evolution reaction,supercapacitors and batteries.
基金the National Key R&D Program of China(2018YFA0703503)the National Natural Science Foundation of China(No.21671016,51872024,and 51932001)the China Postdoctoral Science Foundation(No.2019M650849).
文摘Ammonia borane(AB),with a potential storage capacity of 19.6 wt%H_(2),is an excellent material for chemical storage of hydrogen.However,the use of noble metal catalysts severely hinders the practical application of AB decomposition for hydrogen generation.In this work,well dispersed CuCo and CoO nanoparticles(CuCo(O))supported on carbon–nitrogen frameworks(CN)have been synthesized through a facile thermal reduction of the Cu-doped ZIF67 precursor.Upon reduction,Co and Cu in the ZIF framework are partially reduced into CuCo particles of about 30 nm,and these active species are anchored on porous carbon–nitrogen matrix inherited ZIF frameworks(denoted as CuCo(O)@CN).The as-prepared material demonstrates a ZIF-67-like polyhedral morphology,good nanoparticle spatial distribution and better active site availability.When used as an AB hydrolysis catalyst,CuCo(O)@CN exhibits excellent catalytic activity,with the highest catalytic efficiency up to 4524 mL min^(−1)g^(−1)and a total turnover frequency(TOF)of 12.4 mol H_(2)per min per molcat,which are among the best performances of noble metal-free catalysts.In addition,the corresponding activation energy is estimated to be as low as 33.8 kJ mol^(−1).Detailed analysis suggests that excllent catalytic performance could be attributed to the synergy between Co and Cu as well as the nitrogen-rich carbon support.
