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1.
Crystalline solids with intrinsically low lattice thermal conductivity (κL) are crucial to realizing high‐performance thermoelectric (TE) materials. Herein, we show an ultralow κL of 0.35 Wm?1 K?1 in AgCuTe, which has a remarkable TE figure‐of‐merit, zT of 1.6 at 670 K when alloyed with 10 mol % Se. First‐principles DFT calculation reveals several soft phonon modes in its room‐temperature hexagonal phase, which are also evident from low‐temperature heat‐capacity measurement. These phonon modes, dominated by Ag vibrations, soften further with temperature giving a dynamic cation disorder and driving the superionic transition. Intrinsic factors cause an ultralow κL in the room‐temperature hexagonal phase, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high‐temperature rocksalt phase. Despite the cation disorder at elevated temperatures, the crystalline conduits of the rigid anion sublattice give a high power factor.  相似文献   

2.
To enhance the performance of thermoelectric materials and enable access to their widespread applications, it is beneficial yet challenging to synthesize hollow nanostructures in large quantities, with high porosity, low thermal conductivity (κ ) and excellent figure of merit (z T ). Herein we report a scalable (ca. 11.0 g per batch) and low‐temperature colloidal processing route for Bi2Te2.5Se0.5 hollow nanostructures. They are sintered into porous, bulk nanocomposites (phi 10 mm×h 10 mm) with low κ (0.48 W m−1 K−1) and the highest z T (1.18) among state‐of‐the‐art Bi2Te3−x Sex materilas. Additional benefits of the unprecedented low relative density (68–77 %) are the large demand reduction of raw materials and the improved portability. This method can be adopted to fabricate other porous phase‐transition and thermoelectric chalcogenide materials and will pave the way for the implementation of hollow nanostructures in other fields.  相似文献   

3.
Hierarchically porous carbon materials with high surface areas are promising candidates for energy storage and conversion. Herein, the facile synthesis of hierarchically porous carbons through the calcination of metal–organic framework (MOF)/chitosan composites is reported. The effects of the chitosan (CS) additive on the pore structure of the resultant carbons are discussed. The corresponding MOF/chitosan precursors could be readily converted into hierarchically porous carbons (NPC‐V, V=1, 2, 4, and 6) with much higher ratios of meso‐/macropore volume to micropore volume (Vmeso‐macro/Vmicro). The derived carbon NPC‐2 with the high ratio of Vmeso‐macro/Vmicro=1.47 demonstrates a high specific surface area of 2375 m2 g?1, and a high pore volume of 2.49 cm3 g?1, as well as a high graphitization degree, in comparison to its counterpart (NPC) without chitosan addition. These excellent features are favorable for rapid ion diffusion/transport, endowing NPC‐2 with enhanced electrochemical behavior as supercapacitor electrodes in a symmetric electrode system, corresponding to a high specific capacitance of 199.9 F g?1 in the aqueous electrolyte and good rate capability. Good cycling stability is also observed after 10 000 cycles.  相似文献   

4.
Novel dendrite‐like silver particles were electrodeposited on Ti substrates from a supporting electrolyte‐free 30 mmol L?1 Ag(NH3)2+ solution, to synthesize the den‐Ag/Ti electrode. Binary AgxCoy/Ti electrodes with different Ag:Co atomic ratios were further obtained by electrodeposition of Co particles on the den‐Ag/Ti electrode. Polyaniline (PANI) modified den‐Ag/Ti and AgxCoy/Ti electrodes, PANI(n)‐den‐Ag/Ti and PANI(n)‐AgxCoy/Ti, were also obtained by cyclic voltammetry at different numbers of cycles (n) in acidic and alkaline solutions containing aniline, respectively. All these electrodes exhibit high electroactivity for oxygen reduction reaction (ORR) in alkaline solution and their electroactivities follow the order: PANI(15)‐Ag31Co69/Ti>Ag31Co69/Ti>PANI(20)‐den‐Ag/Ti>den‐Ag/Ti. Among them, PANI(15)‐Ag31Co69/Ti displays the highest electrocatalytic activity for ORR with a much positive onset potential of 0 V (vs. Ag/AgCl) and a high ORR current density of 1.2 mA cm?2 at ?0.12 V (vs. Ag/AgCl). The electrocatalysts are electrochemically insensitive to methanol and ethanol oxidation, and, as cathode electrocatalysts of direct alcohol fuel cells, can resist poisoning by the possible alcohol crossover from the anode.  相似文献   

5.
《化学:亚洲杂志》2017,12(15):1920-1926
An “in situ sacrifice” process was devised in this work as a room‐temperature, all‐solution processed electrochemical method to synthesize nanostructured NiOx and FeOx directly on current collectors. After electrodepositing NiZn/FeZn bimetallic textures on a copper net, the zinc component is etched and the remnant nickel/iron are evolved into NiOx and FeOx by the “in situ sacrifice” activation we propose. As‐prepared electrodes exhibit high areal capacities of 0.47 mA h cm−2 and 0.32 mA h cm−2, respectively. By integrating NiOx as the cathode, FeOx as the anode, and poly(vinyl alcohol) (PVA)‐KOH gel as the separator/solid‐state electrolyte, the assembled quasi‐solid‐state flexible battery delivers a volumetric capacity of 6.91 mA h cm−3 at 5 mA cm−2, along with a maximum energy density of 7.40 mWh cm−3 under a power density of 0.27 W cm−3 and a maximum tested power density of 3.13 W cm−3 with a 2.17 mW h cm−3 energy density retention. Our room‐temperature synthesis, which only consumes minute electricity, makes it a promising approach for large‐scale production. We also emphasize the in situ sacrifice zinc etching process used in this work as a general strategy for metal‐based nanostructure growth for high‐performance battery materials.  相似文献   

6.
Exploring advanced electrocatalysts for electrocatalytic hydrogen evolution is highly desired but remains a challenge due to the lack of an efficient preparation method and reasonable structural design. Herein, we deliberately designed novel Ag/WO3?x heterostructures through a supercritical CO2‐assisted exfoliation‐oxidation route and the subsequent loading of Ag nanoparticles. The ultrathin and oxygen vacancies‐enriched WO3?x nanosheets are ideal substrates for loading Ag nanoparticles, which can largely increase the active site density and improve electron transport. Besides, the resultant WO3?x nanosheets with porous structure can form during the electrochemical cycling process induced by an electric field. As a result, the exquisite Ag/WO3?x heterostructures show an enhanced hydrogen evolution reaction (HER) activity with a low onset overpotential of ≈30 mV, a small Tafel slope of ≈40 mV dec?1 at 10 mA cm?2, and as well as long‐term durability. This work sheds light on material design and preparation, and even opens up an avenue for the development of high‐efficiency electrocatalysts.  相似文献   

7.
Electrochemical splitting of water to produce hydrogen and oxygen is an important process for many energy storage and conversion devices. Developing efficient, durable, low‐cost, and earth‐abundant electrocatalysts for the oxygen evolution reaction (OER) is of great urgency. To achieve the rapid synthesis of transition‐metal nitride nanostructures and improve their electrocatalytic performance, a new strategy has been developed to convert cobalt oxide precursors into cobalt nitride nanowires through N2 radio frequency plasma treatment. This method requires significantly shorter reaction times (about 1 min) at room temperature compared to conventional high‐temperature NH3 annealing which requires a few hours. The plasma treatment significantly enhances the OER activity, as evidenced by a low overpotential of 290 mV to reach a current density of 10 mA cm?2, a small Tafel slope, and long‐term durability in an alkaline electrolyte.  相似文献   

8.
Designing the photoanode structure in dye‐sensitized solar cells (DSSCs) is vital to realizing enhanced power conversion efficiency (PCE). Herein, novel multifunctional silver‐decorated porous titanium dioxide nanofibers (Ag/pTiO2 NFs) made by simple electrospinning, etching, and chemical reduction processes are introduced. The Ag/pTiO2 NFs with a high surface area of 163 m2 g?1 provided sufficient dye adsorption for light harvesting. Moreover, the approximately 200 nm diameter and rough surface of the Ag/pTiO2 NFs offered enough light scattering, and the enlarged interpores among the NFs in the photoanode also permitted electrolyte circulation. Ag nanoparticles (NPs) were well dispersed on the surface of the TiO2 NFs, which prevented aggregation of the Ag NPs after calcination. Furthermore, a localized surface plasmon resonance effect by the Ag NPs served to increase the light absorption at visible wavelengths. The surface area and amount of Ag NPs was optimized. The PCE of pTiO2 NF‐based DSSCs was 27 % higher (from 6.2 to 7.9 %) than for pure TiO2 NFs, whereas the PCE of Ag/pTiO2 NF‐based DSSCs increased by about 12 % (from 7.9 to 8.8 %). Thus, the PCE of the multifunctional pTiO2 NFs was improved by 42 %, that is, from 6.2 to 8.8 %.  相似文献   

9.
We have successfully developed a new process to prepare porous poly(methyl methacrylate-co-acrylonitrile) (P(MMA-AN)) copolymer based gel electrolyte. The porous structure in the polymer matrix is achieved by adding SnO2 nanoparticles which are mostly used as gas sensor materials. The quasi-aromatic solvent, NMP, has an electron-repulsion effect with the space charge layer on the surface of SnO2 nanoparticles and forms a special gas–liquid phase interface. Once the cast polymer solution is stored at an elevated temperature to evaporate the solvent, gas–liquid phase separation happens and spherical pores are obtained. The ionic conductivity at room temperature of the prepared gel polymer electrolyte based on the porous membrane is as high as 1.54 × 10−3 S cm−1 with the electrochemical stability up to 5.10 V (vs. Li/Li+). This method presents another promising way to prepare porous polymer electrolyte for practical use.  相似文献   

10.
Two new organic building units that contain dicarboxylate sites for their self‐assembly with paddlewheel [Cu2(CO2)4] units have been successfully developed to construct two isoreticular porous metal–organic frameworks (MOFs), ZJU‐35 and ZJU‐36, which have the same tbo topologies (Reticular Chemistry Structure Resource (RCSR) symbol) as HKUST‐1. Because the organic linkers in ZJU‐35 and ZJU‐36 are systematically enlarged, the pores in these two new porous MOFs vary from 10.8 Å in HKUST‐1 to 14.4 Å in ZJU‐35 and 16.5 Å in ZJU‐36, thus leading to their higher porosities with Brunauer–Emmett–Teller (BET) surface areas of 2899 and 4014 m2 g?1 for ZJU‐35 and ZJU‐36, respectively. High‐pressure gas‐sorption isotherms indicate that both ZJU‐35 and ZJU‐36 can take up large amounts of CH4 and CO2, and are among the few porous MOFs with the highest volumetric storage of CH4 under 60 bar and CO2 under 30 bar at room temperature. Their potential for high‐pressure swing adsorption (PSA) hydrogen purification was also preliminarily examined and compared with several reported MOFs, thus indicating the potential of ZJU‐35 and ZJU‐36 for this important application. Studies show that most of the highly porous MOFs that can volumetrically take up the greatest amount of CH4 under 60 bar and CO2 under 30 bar at room temperature are those self‐assembled from organic tetra‐ and hexacarboxylates that contain m‐benzenedicarboxylate units with the [Cu2(CO2)4] units, because this series of MOFs can have balanced porosities, suitable pores, and framework densities to optimize their volumetric gas storage. The realization of the two new organic building units for their construction of highly porous MOFs through their self‐assembly with [Cu2(CO2)4] units has provided great promise for the exploration of a large number of new tetra‐ and hexacarboxylate organic linkers based on these new organic building units in which different aromatic backbones can be readily incorporated into the frameworks to tune their porosities, pore structures, and framework densities, thus targeting some even better performing MOFs for very high gas storage and efficient gas separation under high pressure and at room temperature in the near future.  相似文献   

11.
A fluorine‐doped antiperovskite Li‐ion conductor Li2(OH)X (X=Cl, Br) is shown to be a promising candidate for a solid electrolyte in an all‐solid‐state Li‐ion rechargeable battery. Substitution of F? for OH? transforms orthorhombic Li2OHCl to a room‐temperature cubic phase, which shows electrochemical stability to 9 V versus Li+/Li and two orders of magnitude higher Li‐ion conductivity than that of orthorhombic Li2OHCl. An all‐solid‐state Li/LiFePO4 with F‐doped Li2OHCl as the solid electrolyte showed good cyclability and a high coulombic efficiency over 40 charge/discharge cycles.  相似文献   

12.
A doubly interpenetrating porous metal–organic framework ( SNU‐77 ) has been synthesized from the solvothermal reaction of the extended carboxylic acid tris(4′‐carboxybiphenyl)amine (H3TCBPA) and Zn(NO3)2 ? 6H2O in N,N‐dimethylacetamide (DMA). SNU‐77 undergoes single‐crystal‐to‐single‐crystal transformations during various activation processes, such as room‐temperature evacuation, supercritical CO2 drying, and high temperature evacuation, to afford SNU‐77R , SNU‐77S , and SNU‐77H , respectively. These guest‐free MOFs exhibited different fine structures with different window shapes and different effective window sizes at room temperature. Variable‐temperature synchrotron single‐crystal X‐ray analyses reveal that the guest‐free structure is also affected by changes in temperature. Despite the different fine structures, SNU‐77R , SNU‐77S , and SNU‐77H show similar gas sorption properties due to the nonbreathing nature of the framework and an additional structural change upon cooling to cryogenic gas sorption temperature. SNU‐77H exhibits a large surface area (BET, 3670 m2 g?1), a large pore volume (1.52 cm3 g?1), and exceptionally high uptake capacities for N2, H2, O2, CO2, and CH4 gases.  相似文献   

13.
Hierarchical and hollow nanostructures have recently attracted considerable attention because of their fantastic architectures and tunable property for facile lithium ion insertion and good cycling stability. In this study, a one‐pot and unusual carving protocol is demonstrated for engineering hollow structures with a porous shell. Hierarchical TiO2 hollow spheres with nanosheet‐assembled shells (TiO2 NHS) were synthesized by the sequestration between the titanium source and 2,2′‐bipyridine‐5,5′‐dicarboxylic acid, and kinetically controlled etching in trifluoroacetic acid medium. In addition, annealing such porous nanostructures presents the advantage of imparting carbon‐doped functional performance to its counterpart under different atmospheres. Such highly porous structures endow very large specifics surface area of 404 m2 g?1 and 336 m2 g?1 for the as‐prepared and calcination under nitrogen gas. C/TiO2 NHS has high capacity of 204 mA h g?1 at 1 C and a reversible capacity of 105 mA h g?1 at a high rate of 20 C, and exhibits good cycling stability and superior rate capability as an anode material for lithium‐ion batteries.  相似文献   

14.
In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au? M (M=Au, Pd, and Pt) core–shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au? Au, Au? Pd, and Au? Pt core–shell nanostructures with typical porous shells. Moreover, the Au? Au isomeric core–shell nanostructure is reported for the first time. The lower oxidation states of AuI, PdII, and PtII are supposed to contribute to the formation of porous core–shell nanostructures instead of yolk‐shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au? Pd core–shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core–shell nanostructures. As expected, the Au? Pd core–shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (If/Ib is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au? M (M=Au, Pd, and Pt) core–shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface‐enhanced Raman scattering, and so forth.  相似文献   

15.
New poly (vinylidenefluoride-co-hexafluoro propylene) (PVDF-HFP)/CeO2-based microcomposite porous polymer membranes (MCPPM) and nanocomposite porous polymer membranes (NCPPM) were prepared by phase inversion technique using N-methyl 2-pyrrolidone (NMP) as a solvent and deionized water as a nonsolvent. Phase inversion occurred on the MCPPM/NCPPM when it is treated by deionized water (nonsolvent). Microcomposite porous polymer electrolytes (MCPPE) and nanocomposite porous polymer electrolytes (NCPPE) were obtained from their composite porous polymer membranes when immersed in 1.0 M LiClO4 in a mixture of ethylene carbonate/dimethyl carbonate (EC/DMC) (v/v = 1:1) electrolyte solution. The structure and porous morphology of both composite porous polymer membranes was examined by scanning electron microscope (SEM) analysis. Thermal behavior of both MCPPM/NCPPM was investigated from DSC analysis. Optimized filler (8 wt% CeO2) added to the NCPPM increases the porosity (72%) than MCPPM (59%). The results showed that the NCPPE has high electrolyte solution uptake (150%) and maximum ionic conductivity value of 2.47 × 10−3 S cm−1 at room temperature. The NCPPE (8 wt% CeO2) between the lithium metal electrodes were found to have low interfacial resistance (760 Ω cm2) and wide electrochemical stability up to 4.7 V (vs Li/Li+) investigated by impedance spectra and linear sweep voltammetry (LSV), respectively. A prototype battery, which consists of NCPPE between the graphite anode and LiCoO2 cathode, proves good cycling performance at a discharge rate of C/2 for Li-ion polymer batteries.  相似文献   

16.
The highly porous Mn2O3‐Ag nanofibers were fabricated by a facile two‐step procedure (electrospinning and calcination). The structure and composition of the Mn2O3‐Ag nanofibers were characterized by SEM, TEM, XRD, EDX and SAED. The as‐prepared Mn2O3‐Ag nanofibers were then employed as the immobilization matrix for glucose oxidase (GOD) to construct an amperometric glucose biosensor. The biosensor shows fast response to glucose, high sensitivity (40.60 µA mM?1 cm?2), low detection limit (1.73 µM at S/N=3), low Km,app value and excellent selectivity. These results indicate that the novel Mn2O3‐Ag nanfibers‐GOD composite has great potential application in oxygen‐reduction based glucose biosensing.  相似文献   

17.
Two new dithioether ligands, 1,4‐bis[(phenylsulfanyl)methyl]naphthalene ( L1 ), and 4,4′‐bis[(tert‐butylsulfanyl)methyl]biphenyl ( L2 ) were synthesized and their silver(I) complexes were studied. Both AgI complexes, [Ag L1 (NO3)]n ( 1 ) and [Ag L2 (NO3)]2 ( 2 ), were synthesized at ambient temperature and characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction analysis. Single‐crystal X‐ray analysis shows that complex 1 has a one‐dimensional helical chain structure with the neutral repeating unit [Ag(μ2‐ L1 )(NO3)], whereas complex 2 has a centrosymmetrical neutral dinuclear structure. Moreover, complexes 1 and 2 are further extended into three‐dimensional supramolecular frameworks by hydrogen bonding and π–π stacking interactions, respectively. In addition, complexes 1 and 2 display strong blue emission in the solid state at room temperature.  相似文献   

18.
The synergistic Ag+/X2 system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X2 or Ag+ alone. Intermediates for its action may include [Agm(X2)n]m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I2‐Ag( A ), [Ag2(I2)4]2+( A ?)2 and [Ag2(I2)6]2+( A ?)2?(I2)x≈0.65 form by reaction of Ag( A ) ( A =Al(ORF)4; RF=C(CF3)3) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I2‐Ag( A ) is ideally set up to act as a 2 e? oxidant with stoichiometric formation of 2 AgI and 2 A ?. Preliminary reactivity tests proved this ( A )Ag‐I2‐Ag( A ) starting material to oxidize n‐C5H12, C3H8, CH2Cl2, P4 or S8 at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF6 (M=4d metals). This suggests that ( A )Ag‐I2‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.  相似文献   

19.
Reference electrodes for room temperature ionic liquid (RTIL) applications were constructed that have a known and reproducible potential versus the ferrocene/ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag+ couple type, or of the second kind, based on Ag/AgCl in M+Cl?. The former uses AgNO3 salt and the latter tetrabutylammonium chloride, Bu4NCl, dissolved in acetonitrile which are then introduced to the ionic liquid of choice for a final concentration of 0.1 M. The reference electrodes can be easily and reproducibly constructed. An ionic contact of these reference systems with the test electrolyte was made using an asbestos fiber liquid junction. The internal compartment of the reference system was filled with the same ionic liquid as used for the electrochemical experiment. The performance of these reference electrodes was tested in selected ionic liquids using the ferrocene/ferrocenium redox couple. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized in the following ionic liquids: 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIBF4), 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI(CF3SO2)2N), and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIPF6). It has been found that the formal potentials of the examined reference systems are stable over several days. There is a linear relationship for the temperature studied in the range from 25 to 60 °C.  相似文献   

20.
The synergistic Ag+/X2 system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X2 or Ag+ alone. Intermediates for its action may include [Agm(X2)n]m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I2‐Ag( A ), [Ag2(I2)4]2+( A )2 and [Ag2(I2)6]2+( A )2⋅(I2)x≈0.65 form by reaction of Ag( A ) ( A =Al(ORF)4; RF=C(CF3)3) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I2‐Ag( A ) is ideally set up to act as a 2 e oxidant with stoichiometric formation of 2 AgI and 2 A . Preliminary reactivity tests proved this ( A )Ag‐I2‐Ag( A ) starting material to oxidize n‐C5H12, C3H8, CH2Cl2, P4 or S8 at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF6 (M=4d metals). This suggests that ( A )Ag‐I2‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.  相似文献   

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