Herein, we demonstrated the oriented attachment (OA) driven formation and characterization of Gd2O3 nanorods. The nanorods were synthesized via a surfactant free, inexpensive hydrothermal route and considering ~30 nm ...Herein, we demonstrated the oriented attachment (OA) driven formation and characterization of Gd2O3 nanorods. The nanorods were synthesized via a surfactant free, inexpensive hydrothermal route and considering ~30 nm nanoparticles as the seed. While maintaining a cubic phase throughout the process, complete transformation of Gd2O3nanoparticles to nanorods was found to occur at an elevated temperature (~180 oC) of the hydrothermal reaction. The elongated Gd2O3 nanostructures, as revealed from transmission electron microscopic imaging, possessed an average diameter of ~33 nm and an approximate length of 172 nm. From the kinetics of OA process, the activation energy of formation was estimated to be ~25 kJ/mole. The existence of defect mediated radia-tive emission was ascertained from the asymmetric broadening of luminescence spectra. The defect emission arising from the Gd2O3 nanorods was nearly 1.4 times stronger than that of nanoparticles. The morphological evolution and growth kinetics were discussed along with the luminescence and electron paramagnetic resonance features.展开更多
Spindle-shaped anatase TiO2 secondary particles were successfully fabricated via the oriented attachment of primary nanocrystals. By adjusting the concentration of tetrabutyl titanate, the size of the TiO2 nanocrystal...Spindle-shaped anatase TiO2 secondary particles were successfully fabricated via the oriented attachment of primary nanocrystals. By adjusting the concentration of tetrabutyl titanate, the size of the TiO2 nanocrystals and particles could be controlled, resulting in pore evolution. Pores for the random aggregation of secondary particles gradually transformed to nanopores originating from the oriented attachment of the primary nanocrystals, resulting in an excellent micro/nanostructure that increased the performance of a sodium-ion battery. The mesoporous TiO2 microparticle anode, with its unique combination of nanocrystals and uniform nanopores, displays super durability （95 mAh/g after 11,000 cycles at I C）, high initial efficiency （61.4%）, and excellent rate performance （265 and 77 mAh/g at 0.1 and 20 C, respectively）. In particular, at slow discharge （0.1 C） and fast charge （5, 50, and 100 C） rates, the anatase TiO2 shows remarkable initial charge capacities of 200, 119, and 56 mAh/g, corresponding to 172, 127, and 56 mAh/g, after 150 cycles, respectively, thus meeting the requirements for fast energy storage. This excellent performance can be attributed to the stability of the material and its high ionic conductivity, resulting from the stable architecture with a mesoporous microstructure and without the random aggregation of secondary particles. A fundamental understanding of the pore structure and controllable pore construction has been proven to be effective in increasing the rate capability and durability of nanostructured electrode materials.展开更多
Oriented attachment and Ostwald ripening are two aging mechanisms of precipitation particles which may result in differ- ent crystallization mechanism of precipitates during the aging process. In this work, the effect...Oriented attachment and Ostwald ripening are two aging mechanisms of precipitation particles which may result in differ- ent crystallization mechanism of precipitates during the aging process. In this work, the effects of different aging process on the structure and properties of cerium zirconium mixed oxides were investigated. The results indicated that the mixed structure of 11.48% CeO2 phase and 88.52% Ce0.26Zr0.62（LaPr）0.1202 solid solution phase were obtained under oriented attachment aging process. The rod-like CeO2 phase coexisted with spherical Ce0.26Zr0.62（LaPr）0.1202 solid solution phase, which improved the surface area （64 m2/g） and pore volume （0.32 mL/g） of cerium zirconium mixed oxides after 1000 ℃ 4 h thermal treatment. However, through controlling the aging process, the Ce0.35Zr0.55（LaPr）0.1002 solid solution with homogenous phase structure was generated by Ostwald ripening ag- ing process, exhibiting higher oxygen storage capacity （501 μmol O2/g） and H2 consumption per gram （1378.3 μmol H2/g）.展开更多
Alloying of metals is known from antiquity. Alloy making <em>i.e.</em>, homogenizing metals started in a “hit-or-miss” way. The 1</span><sup><span style="font-family:Verdana;">...Alloying of metals is known from antiquity. Alloy making <em>i.e.</em>, homogenizing metals started in a “hit-or-miss” way. The 1</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> alloy from copper (Cu) and tin (Sn) was produced around 2500 BC and from then Bronze Age began. Subsequently iron (Fe) age started after the Bronze Age. Aluminium (Al) alloying was discovered much later because pure Al could not be recovered easily even though Al is the most abundant metal in the earth’s crust. Refining of Al is a very difficult job because of its strong affinity towards oxygen. To ease alloying, melting points (mp) of the individual constituents and reactivity of metal towards oxygen were the hurdles. Now understanding the thermodynamics of metal mixing has paved alloying. Periodic properties of elements concerning size, electronegativity, crystal structure, valency, lattice spacing, etc. are considered for alloying. In this feature article, more emphasis is given to Hume-Rothery rules in which the necessary parameters for alloying have been illustrated. Importantly standard electrode potential (E</span><sup><span style="font-family:Verdana;">0</span></sup><span style="font-family:Verdana;">) values, eutectic, phase diagram, size-related strain in metals, etc. have been looked into in the present discussion. One elegant example is Sn-Pb alloy, known as soft solder. Soft solder was in use for many years to connect metals and in electric circuitry. Low melting, flowability, and conductivity of soft solder had placed Sn-Pb alloy a unique position in industries, laboratories and even in cottage industries. However, toxic Pb volatilizes during soldering and hence soft solder is banned almost in all countries. We felt the need for a viable alternative to obtain soldering material and then silver (Ag) based highly conducting, an eco-friendly alloy of Sn resulted in from a high boiling liquid. The discovery engenders not only a new conducting soldering alloy but also a new concept of melting metals together. Furthermore, new ideas of alloying have been generalized at their nanostages from a suitable high boiling solvent.展开更多
Quantum dots,semiconductor crystals with nanometer-scale dimensions,exhibit adjustable chemical,electrical,and optical characteristics owing to the quantum confinement effect.However,achieving high-quality quantum dot...Quantum dots,semiconductor crystals with nanometer-scale dimensions,exhibit adjustable chemical,electrical,and optical characteristics owing to the quantum confinement effect.However,achieving high-quality quantum dots necessitates simultaneous attainment of crystalline integrity within their cores,uniformity in size and shape,as well as effective surface passivation with charge transport functionality—challenges persist regardless of the chosen method.Here,we introduce a novel approach for synthesizing quantum-dot/perovskite heterocrystals:the Colloidal Quantum Dot-Oriented Attachment to Perovskite Single Crystal(CQD-OA-PSC)method.This method involves optimizing quantum dot growth through chemical colloidal synthesis methods,followed by their oriented attachment onto macroscopic perovskite single crystals with impeccable lattice alignment.Consequently,the CQD-OA-PSC method amalgamates the strengths of wet chemical colloidal synthesis methods and solution-based epitaxial growth,offering precise control over quantum dot size,morphology,and structure while leveraging charge transport functionality conferred by the matrix crystal.High-resolution transmission electron microscopy confirms matched lattice orientations between the perovskite matrix and quantum dots.This approach promises to yield high-quality quantum dots perovskite heterocrystals with controlled size,morphology,and optoelectronic properties,thereby holding significant potential for advancing the development of efficient optoelectronic devices.展开更多
To address the insufficient electrocatalytic activity and stability of formic acid oxidation reaction （FAOR） electrocatalysts, as well as their high cost, we herein demonstrate the facile hydrothermal synthesis of u...To address the insufficient electrocatalytic activity and stability of formic acid oxidation reaction （FAOR） electrocatalysts, as well as their high cost, we herein demonstrate the facile hydrothermal synthesis of ultrathin AgPt alloy nanowires using amine-terminated poly（N-isopropylacrylamide） （PNIPAM-NH2） as a structure-directing agent. The initial generation of AgC1 precipitates, subsequent formation of AgPt nanoparticles, and their oriented attachment account for the formation of ultrathin AgPt alloy nanowires. Benefiting from their unique one-dimensional （1D） anisotropy and alloyed composition, the prepared ultrathin AgPt nanowires exhibit a superior electrocatalytic activity and better CO tolerance for the FAOR, reaching a 1.6-fold and 3.7-fold higher specific current density than AgPt nanoparticles and a commercial Pt black catalyst, respectively. Additionally, the ultrathin AgPt alloy nanowires manifest a superior electrochemical stability and structural robustness during electrocatalysis, making them a promising FAOR electrocatalyst. This work not only provides a reliable strategy for the synthesis of noble metal-based ultrathin nanowires, but also opens an avenue towards the rational des ign of efficient electrocatalysts for fuel cell systems.展开更多
Mesocrystals, which are assemblies of crystallographically oriented nanocrystals, have received increasing attention due to their unique properties such as high crystallinity, high porosity, oriented subunit alignment...Mesocrystals, which are assemblies of crystallographically oriented nanocrystals, have received increasing attention due to their unique properties such as high crystallinity, high porosity, oriented subunit alignment, and similarity to highly sophisticated biominerals. However, the controlled synthesis of TiO 2 mesocrystals has not been realized until recently, probably because of the difficulty in accurately controlling the reaction processes that produce TiO 2 crystals. In this review, recent advances in the synthesis and applications of TiO 2 mesocrystals are summarized with particular attention paid to the mechanisms of their formation. Three typical pathways for the preparation of TiO 2 mesocrystals are discussed, namely topotactic transformation, direct synthesis in solution, and growth on supports. The potential applications of TiO 2 mesocrystals in lithium ion batteries, photocatalysis, enzyme immobilization, and antireflection materials are also described.展开更多
Ultrathin nanostructures have attracted much attention in recent years due to their predictable novel properties and various potential applications. The improvement in synthetic skills has led to many successful synth...Ultrathin nanostructures have attracted much attention in recent years due to their predictable novel properties and various potential applications. The improvement in synthetic skills has led to many successful syntheses of nanostructures including zerodimensional (0D) nanoclusters, one-dimensional (1D) nanowires, two-dimensional (2D) nanosheets and other higher-level complex nanostructures, where cluster-assembly of primary nanocrystals is a common process. In this review, progress in ultrathin nanocrystals in the last decade and several important factors in the growth mechanisms are covered. By giving examples of cluster assembly from 1D to 3D nanostructures, the utility of cluster assembly in the synthesis of new materials has been demonstrated.展开更多
The procedure reported here allows for the size and shape control of CdTe nanowires by means of colloidal chemistry. Thus, ultrathin, straight, saw-tooth-like and one-sided branched nanowires with zinc blende structur...The procedure reported here allows for the size and shape control of CdTe nanowires by means of colloidal chemistry. Thus, ultrathin, straight, saw-tooth-like and one-sided branched nanowires with zinc blende structures could be synthesized. Their formation does not require any catalyst and is most likely due to the oriented attachment of nanoparticles formed in the beginning of the reaction. The use of oleylamine as a solvent turned out to be crucial in order to achieve CdTe nanowires. The reaction between oleic acid and oleylamine in the presence of CdO proved to be essential, not only to activate the Cd precursor but also to provide reaction conditions facilitating nanowire formation by oriented attachment.展开更多
Electrochemical upgrading of biomass ethanol to value-added chemicals is promising for sustainable society.Here,we synthesize defective Ni_(3)S_(2) nanowires(NWs),which show high activity towards electrochemical oxida...Electrochemical upgrading of biomass ethanol to value-added chemicals is promising for sustainable society.Here,we synthesize defective Ni_(3)S_(2) nanowires(NWs),which show high activity towards electrochemical oxidation of ethanol to acetate.The Ni_(3)S_(2) NWs are formed by the oriented attachment mechanism,and rich defects are introduced during the growth.A low onset potential of 1.31 V and high mass activity of 8,716 mA·mgNi^(-1) at 1.5 V are achieved using the synthesized Ni_(3)S_(2) NWs toward the ethanol electro-oxidation,which are better than the Ni(OH)2 NWs and the Ni_(3)S_(2) nanoparticles(NPs).And the selectivity for the acetate generation is ca.99%.The high activity of Ni_(3)S_(2) NWs is attributed to the easier oxidation of Ni(II)to the catalytically active Ni(III)species with the promotion from S component and rich defects.These results demonstrate that the defective NWs can be synthesized by the oriented attachment method and the defective Ni_(3)S_(2) NWs structure as the efficient nonnoble metal electrocatalysts for oxidative upgrading of ethanol.展开更多
Oriented attachment can be used as a good synthetic route to make highly anisotropic nanostructures including nanorod,nanowire,nanoplate,and nanosheets.In a typical growth of anisotropic nanostructures,coalescence and...Oriented attachment can be used as a good synthetic route to make highly anisotropic nanostructures including nanorod,nanowire,nanoplate,and nanosheets.In a typical growth of anisotropic nanostructures,coalescence and reshaping after attachment make dense nanostructures.In this report,we show the formation of Ag sheets having fractal network by oriented attachment at low reaction temperature of 30℃.The synthesized Ag sheets exhibited good crystalline nature despite of their network structure and low synthetic temperature.We also investigated the effect of reaction conditions for the formation of the Ag sheets.In addition,using the Ag sheets as a sacrificial template,we could make hollow Au sheets via galvanic replacement.展开更多
Exposed crystal facets directly affect the electrochemical/catalytic performance of MnO2 materials during their applications in supercapacitors, rechargeable batteries, and fuel cells. Currently, the facet-controlled ...Exposed crystal facets directly affect the electrochemical/catalytic performance of MnO2 materials during their applications in supercapacitors, rechargeable batteries, and fuel cells. Currently, the facet-controlled synthesis of MnO2 is facing serious challenges due to the lack of an in-depth understanding of their surface evolution mechanisms. Here, combining aberration-corrected scanning transmission electron microscopy （STEM） and high-resolution TEM, we revealed a mutual energy-driven mechanism between beta-MnO2 nanowires and microstructures that dominated the evolution of the lateral facets in both structures. The evolution of the lateral surfaces followed the elimination of the {100} facets and increased the occupancy of {110} facets with the increase in hydrothermal retention time. Both self-growth and oriented attachment along their {100} facets were observed as two different ways to reduce the surface energies of the beta-MnO2 structures. High-density screw dislocations with the 1/2〈100〉 Burgers vector were generated consequently. The observed surface evolution phenomenon offers guidance for the facet-controlled growth of beta- MnO2 materials with high performances for its application in metal-air batteries, fuel cells, supercapacitors, etc.展开更多
基金supported by University Grants Commission(UGC)New Delhi(37-367/2009(SR))
文摘Herein, we demonstrated the oriented attachment (OA) driven formation and characterization of Gd2O3 nanorods. The nanorods were synthesized via a surfactant free, inexpensive hydrothermal route and considering ~30 nm nanoparticles as the seed. While maintaining a cubic phase throughout the process, complete transformation of Gd2O3nanoparticles to nanorods was found to occur at an elevated temperature (~180 oC) of the hydrothermal reaction. The elongated Gd2O3 nanostructures, as revealed from transmission electron microscopic imaging, possessed an average diameter of ~33 nm and an approximate length of 172 nm. From the kinetics of OA process, the activation energy of formation was estimated to be ~25 kJ/mole. The existence of defect mediated radia-tive emission was ascertained from the asymmetric broadening of luminescence spectra. The defect emission arising from the Gd2O3 nanorods was nearly 1.4 times stronger than that of nanoparticles. The morphological evolution and growth kinetics were discussed along with the luminescence and electron paramagnetic resonance features.
文摘Spindle-shaped anatase TiO2 secondary particles were successfully fabricated via the oriented attachment of primary nanocrystals. By adjusting the concentration of tetrabutyl titanate, the size of the TiO2 nanocrystals and particles could be controlled, resulting in pore evolution. Pores for the random aggregation of secondary particles gradually transformed to nanopores originating from the oriented attachment of the primary nanocrystals, resulting in an excellent micro/nanostructure that increased the performance of a sodium-ion battery. The mesoporous TiO2 microparticle anode, with its unique combination of nanocrystals and uniform nanopores, displays super durability （95 mAh/g after 11,000 cycles at I C）, high initial efficiency （61.4%）, and excellent rate performance （265 and 77 mAh/g at 0.1 and 20 C, respectively）. In particular, at slow discharge （0.1 C） and fast charge （5, 50, and 100 C） rates, the anatase TiO2 shows remarkable initial charge capacities of 200, 119, and 56 mAh/g, corresponding to 172, 127, and 56 mAh/g, after 150 cycles, respectively, thus meeting the requirements for fast energy storage. This excellent performance can be attributed to the stability of the material and its high ionic conductivity, resulting from the stable architecture with a mesoporous microstructure and without the random aggregation of secondary particles. A fundamental understanding of the pore structure and controllable pore construction has been proven to be effective in increasing the rate capability and durability of nanostructured electrode materials.
基金Project supported by the Twelfth Five-Year National Science and Technology Pillar Program(2012BAE01B02,2012BAB10B11)
文摘Oriented attachment and Ostwald ripening are two aging mechanisms of precipitation particles which may result in differ- ent crystallization mechanism of precipitates during the aging process. In this work, the effects of different aging process on the structure and properties of cerium zirconium mixed oxides were investigated. The results indicated that the mixed structure of 11.48% CeO2 phase and 88.52% Ce0.26Zr0.62（LaPr）0.1202 solid solution phase were obtained under oriented attachment aging process. The rod-like CeO2 phase coexisted with spherical Ce0.26Zr0.62（LaPr）0.1202 solid solution phase, which improved the surface area （64 m2/g） and pore volume （0.32 mL/g） of cerium zirconium mixed oxides after 1000 ℃ 4 h thermal treatment. However, through controlling the aging process, the Ce0.35Zr0.55（LaPr）0.1002 solid solution with homogenous phase structure was generated by Ostwald ripening ag- ing process, exhibiting higher oxygen storage capacity （501 μmol O2/g） and H2 consumption per gram （1378.3 μmol H2/g）.
文摘Alloying of metals is known from antiquity. Alloy making <em>i.e.</em>, homogenizing metals started in a “hit-or-miss” way. The 1</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> alloy from copper (Cu) and tin (Sn) was produced around 2500 BC and from then Bronze Age began. Subsequently iron (Fe) age started after the Bronze Age. Aluminium (Al) alloying was discovered much later because pure Al could not be recovered easily even though Al is the most abundant metal in the earth’s crust. Refining of Al is a very difficult job because of its strong affinity towards oxygen. To ease alloying, melting points (mp) of the individual constituents and reactivity of metal towards oxygen were the hurdles. Now understanding the thermodynamics of metal mixing has paved alloying. Periodic properties of elements concerning size, electronegativity, crystal structure, valency, lattice spacing, etc. are considered for alloying. In this feature article, more emphasis is given to Hume-Rothery rules in which the necessary parameters for alloying have been illustrated. Importantly standard electrode potential (E</span><sup><span style="font-family:Verdana;">0</span></sup><span style="font-family:Verdana;">) values, eutectic, phase diagram, size-related strain in metals, etc. have been looked into in the present discussion. One elegant example is Sn-Pb alloy, known as soft solder. Soft solder was in use for many years to connect metals and in electric circuitry. Low melting, flowability, and conductivity of soft solder had placed Sn-Pb alloy a unique position in industries, laboratories and even in cottage industries. However, toxic Pb volatilizes during soldering and hence soft solder is banned almost in all countries. We felt the need for a viable alternative to obtain soldering material and then silver (Ag) based highly conducting, an eco-friendly alloy of Sn resulted in from a high boiling liquid. The discovery engenders not only a new conducting soldering alloy but also a new concept of melting metals together. Furthermore, new ideas of alloying have been generalized at their nanostages from a suitable high boiling solvent.
基金supported by National Natural Science Foundation of China(grant nos.12225402,91950115,11774014,62321004)national Key R&D Program of China(grant nos.2022YFA1404700,2018YFA0704401)the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Quantum dots,semiconductor crystals with nanometer-scale dimensions,exhibit adjustable chemical,electrical,and optical characteristics owing to the quantum confinement effect.However,achieving high-quality quantum dots necessitates simultaneous attainment of crystalline integrity within their cores,uniformity in size and shape,as well as effective surface passivation with charge transport functionality—challenges persist regardless of the chosen method.Here,we introduce a novel approach for synthesizing quantum-dot/perovskite heterocrystals:the Colloidal Quantum Dot-Oriented Attachment to Perovskite Single Crystal(CQD-OA-PSC)method.This method involves optimizing quantum dot growth through chemical colloidal synthesis methods,followed by their oriented attachment onto macroscopic perovskite single crystals with impeccable lattice alignment.Consequently,the CQD-OA-PSC method amalgamates the strengths of wet chemical colloidal synthesis methods and solution-based epitaxial growth,offering precise control over quantum dot size,morphology,and structure while leveraging charge transport functionality conferred by the matrix crystal.High-resolution transmission electron microscopy confirms matched lattice orientations between the perovskite matrix and quantum dots.This approach promises to yield high-quality quantum dots perovskite heterocrystals with controlled size,morphology,and optoelectronic properties,thereby holding significant potential for advancing the development of efficient optoelectronic devices.
文摘To address the insufficient electrocatalytic activity and stability of formic acid oxidation reaction （FAOR） electrocatalysts, as well as their high cost, we herein demonstrate the facile hydrothermal synthesis of ultrathin AgPt alloy nanowires using amine-terminated poly（N-isopropylacrylamide） （PNIPAM-NH2） as a structure-directing agent. The initial generation of AgC1 precipitates, subsequent formation of AgPt nanoparticles, and their oriented attachment account for the formation of ultrathin AgPt alloy nanowires. Benefiting from their unique one-dimensional （1D） anisotropy and alloyed composition, the prepared ultrathin AgPt nanowires exhibit a superior electrocatalytic activity and better CO tolerance for the FAOR, reaching a 1.6-fold and 3.7-fold higher specific current density than AgPt nanoparticles and a commercial Pt black catalyst, respectively. Additionally, the ultrathin AgPt alloy nanowires manifest a superior electrochemical stability and structural robustness during electrocatalysis, making them a promising FAOR electrocatalyst. This work not only provides a reliable strategy for the synthesis of noble metal-based ultrathin nanowires, but also opens an avenue towards the rational des ign of efficient electrocatalysts for fuel cell systems.
基金supported by the National Natural Science Foundation of China (21073005, 21173010, and 51121091)National Basic Research Program of China (973 Program, 2007CB936201)
文摘Mesocrystals, which are assemblies of crystallographically oriented nanocrystals, have received increasing attention due to their unique properties such as high crystallinity, high porosity, oriented subunit alignment, and similarity to highly sophisticated biominerals. However, the controlled synthesis of TiO 2 mesocrystals has not been realized until recently, probably because of the difficulty in accurately controlling the reaction processes that produce TiO 2 crystals. In this review, recent advances in the synthesis and applications of TiO 2 mesocrystals are summarized with particular attention paid to the mechanisms of their formation. Three typical pathways for the preparation of TiO 2 mesocrystals are discussed, namely topotactic transformation, direct synthesis in solution, and growth on supports. The potential applications of TiO 2 mesocrystals in lithium ion batteries, photocatalysis, enzyme immobilization, and antireflection materials are also described.
基金supported by the National Natural Science Foundation of China (91127040, 20921001)the National Basic Research Program of China (973 Program, 2011CB932402)
文摘Ultrathin nanostructures have attracted much attention in recent years due to their predictable novel properties and various potential applications. The improvement in synthetic skills has led to many successful syntheses of nanostructures including zerodimensional (0D) nanoclusters, one-dimensional (1D) nanowires, two-dimensional (2D) nanosheets and other higher-level complex nanostructures, where cluster-assembly of primary nanocrystals is a common process. In this review, progress in ultrathin nanocrystals in the last decade and several important factors in the growth mechanisms are covered. By giving examples of cluster assembly from 1D to 3D nanostructures, the utility of cluster assembly in the synthesis of new materials has been demonstrated.
文摘The procedure reported here allows for the size and shape control of CdTe nanowires by means of colloidal chemistry. Thus, ultrathin, straight, saw-tooth-like and one-sided branched nanowires with zinc blende structures could be synthesized. Their formation does not require any catalyst and is most likely due to the oriented attachment of nanoparticles formed in the beginning of the reaction. The use of oleylamine as a solvent turned out to be crucial in order to achieve CdTe nanowires. The reaction between oleic acid and oleylamine in the presence of CdO proved to be essential, not only to activate the Cd precursor but also to provide reaction conditions facilitating nanowire formation by oriented attachment.
基金This work was supported by the National Natural Science Foundation of China(No.21971008)the Fundamental Research Funds for the Central Universities(buctrc201916,buctrc201823).
文摘Electrochemical upgrading of biomass ethanol to value-added chemicals is promising for sustainable society.Here,we synthesize defective Ni_(3)S_(2) nanowires(NWs),which show high activity towards electrochemical oxidation of ethanol to acetate.The Ni_(3)S_(2) NWs are formed by the oriented attachment mechanism,and rich defects are introduced during the growth.A low onset potential of 1.31 V and high mass activity of 8,716 mA·mgNi^(-1) at 1.5 V are achieved using the synthesized Ni_(3)S_(2) NWs toward the ethanol electro-oxidation,which are better than the Ni(OH)2 NWs and the Ni_(3)S_(2) nanoparticles(NPs).And the selectivity for the acetate generation is ca.99%.The high activity of Ni_(3)S_(2) NWs is attributed to the easier oxidation of Ni(II)to the catalytically active Ni(III)species with the promotion from S component and rich defects.These results demonstrate that the defective NWs can be synthesized by the oriented attachment method and the defective Ni_(3)S_(2) NWs structure as the efficient nonnoble metal electrocatalysts for oxidative upgrading of ethanol.
基金This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science,ICT,&Future Planning(2014R1A5A1009799)by a National Research Foundation of Korea grant funded by the Korean government(MSIP)(NRF-2015R1C1A1A01054109 and NRF-2016M3D1A1021140).
文摘Oriented attachment can be used as a good synthetic route to make highly anisotropic nanostructures including nanorod,nanowire,nanoplate,and nanosheets.In a typical growth of anisotropic nanostructures,coalescence and reshaping after attachment make dense nanostructures.In this report,we show the formation of Ag sheets having fractal network by oriented attachment at low reaction temperature of 30℃.The synthesized Ag sheets exhibited good crystalline nature despite of their network structure and low synthetic temperature.We also investigated the effect of reaction conditions for the formation of the Ag sheets.In addition,using the Ag sheets as a sacrificial template,we could make hollow Au sheets via galvanic replacement.
文摘Exposed crystal facets directly affect the electrochemical/catalytic performance of MnO2 materials during their applications in supercapacitors, rechargeable batteries, and fuel cells. Currently, the facet-controlled synthesis of MnO2 is facing serious challenges due to the lack of an in-depth understanding of their surface evolution mechanisms. Here, combining aberration-corrected scanning transmission electron microscopy （STEM） and high-resolution TEM, we revealed a mutual energy-driven mechanism between beta-MnO2 nanowires and microstructures that dominated the evolution of the lateral facets in both structures. The evolution of the lateral surfaces followed the elimination of the {100} facets and increased the occupancy of {110} facets with the increase in hydrothermal retention time. Both self-growth and oriented attachment along their {100} facets were observed as two different ways to reduce the surface energies of the beta-MnO2 structures. High-density screw dislocations with the 1/2〈100〉 Burgers vector were generated consequently. The observed surface evolution phenomenon offers guidance for the facet-controlled growth of beta- MnO2 materials with high performances for its application in metal-air batteries, fuel cells, supercapacitors, etc.
