首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
MnCo2O4.5 pod-like microstructures were successfully prepared through an initial solvothermal reaction in a mixed solvent containing water and ethanol, and combined with a subsequent calcinations treatment of the precursors in air. The total synthetic process was accomplished without any surfactant or template participation. The MnCo2O4.5 pods possessed a specific surface area as high as 73.7 m2/g and a mean pore size of 12.3 nm. The electrochemical performances were evaluated in a typical three-electrode system using 2 M of KOH aqueous electrolyte. The results demonstrated that such MnCo2O4.5 pods delivered a specific capacitance of 321 F/g at 1 A/g with a rate capability of 69.5% at 10 A/g. Moreover, the capacitance retention could reach 87% after 4000 cycles at 3 A/g, suggesting the excellent long-term cycling stability. Furthermore, the asymmetric device was fabricated by using MnCo2O4.5 porous pods as anode and active carbon as cathode. It could deliver a specific capacitance of 55.3 F g−1 at 1 A g−1 and an energy density of 19.65 W h kg−1 at a power density of 810.64 W kg−1. Such superior electrochemical behaviors indicate that the MnCo2O4.5 pods may be served as a promising electrode material for the practical applications of high-performance supercapacitors. The current synthesis is simple and cost-effective, and can be extended to the preparation of other binary metal oxides with excellent electrochemical properties.  相似文献   

2.
Tetra-carboxylic acid based 3D porous MOFs 1 and 2, named {[Co2.5(L)]·5H2O}n and 0.5{[Cu(L)]·2H2O}n (L = 4,4′-di(ethoxy)biphenyl-3,3′,5,5′-tetra-(phenyl-4-carboxylic acid)), bearing metal clusters have been facilely constructed by hydrothermal synthesis. Structural studies indicate that 1 presents a 3-nodal (4, 4, 8)-connected topology with the point notation of {44.62}2{48.67.813}, while 2 shows a uninodal (4, 4)-connected network with point symbol of {44.62}. The pristine MOFs are directly utilized for electrocatalysis and poor HER activities are obtained in alkaline solution, which promote the further design and fabrication of a mixed-metal Co/Cu-MOF (3). As expected, 3 shows significantly improved performances for HER with overpotential of 391 mV (10 mA cm−2 current density), low Tafel slope of 94 mV dec−1 and long-term operation stability (14 h). More importantly, the direct utilization of 3 for accelerating OER also presents a fascinating performance in overpotential at 10 mA cm−2 current and durability. The above electrocatalytic performance of pristine 3 can be ascribed to the result of hybridizing strategy for constructing MOFs under hydrothermal procedure, which may favorably produces synergistic effect and more open metal sites. This work provides in-depth understanding of hybrid pristine MOFs for electrocatalysis.  相似文献   

3.
Pulse electrolysis of water is a highly efficient method of production of hydrogen and hydrogen/oxygen gas mixtures, sometimes called hydroxygen. In conditions of pulse electrolysis, the process rate is reported to increase in comparison to the dc regime, which poses more stringent requirements to the corrosion resistance of the electrode materials. The processes of their corrosion and degradation are expected to depend on the electrical characteristics of the pulse (nominal current/voltage, frequency, duty cycle). The aim of the present paper is to investigate the effect of pulse characteristics on the electrochemical properties of surface films formed on AISI 316 stainless steel using voltammetry and electrochemical impedance spectroscopy. An attempt to correlate these properties with the surface state obtained from microscopic observations and X-ray photoelectron spectroscopic estimations of the surface film composition is also made.  相似文献   

4.
A glassy carbon (GC)/graphene/ferritin/glucose oxidase (GOx) anode was developed by using graphene/ferritin biocomposite as an electron transfer enhancer and mediator, respectively. The electrode exhibited good electrocatalytic activity towards the oxidation of glucose. The electrocatalytic oxidation of glucose using GOx modified electrode increased with increasing the concentration of glucose upto 45 mM. The results showed that the graphene/ferritin biocomposite mediator provides enhancement in electron transfer generated at the active cites of GOx to the electrode. All electrochemical measurements were carried out by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). A saturation current density of 66.5 ± 2 mA cm−2 at scan rate 100 mV s−1 for the oxidation of 45 mM glucose was achieved.  相似文献   

5.
In this paper, porous CuCo2O4/CuO composites with novel honeysuckle-like shape (CuCo2O4/CuO HCs) have been prepared for the first time by a simple hydrothermal method and followed with an additional annealing process in air. The unique CuCo2O4/CuO HCs consisted of dense and slender petals with length of 1.3–1.5 μm and width of about 50 nm, and possessed a specific surface area of 36.09 m2 g?1 with main pore size distribution at 10.63 nm. When used as the electrode materials for supercapacitors, the CuCo2O4/CuO HCs exhibited excellent electrochemical performances with a high specific capacity of 350.69 C g?1 at 1 A g?1, a rate capability of 78.6% at 10 A g?1, and 96.2% capacity retention after 5000 cycles at a current density of 5 A g?1. In addition, a hybrid supercapacitor (CuCo2O4/CuO HCs//AC HSC) was assembled using the CuCo2O4/CuO HCs as positive electrode and activated carbon (AC) as negative electrode. The HSC device delivered a specific capacity of 187.85 C g?1 at 1 A g?1 and a superior cycling stability with 104.7% capacity retention after 5000 cycles at 5 A g?1, and possessed a high energy density of 41.76 W h kg?1 at a power density of 800.27 W kg?1. These outstanding electrochemical performances manifested the great potential of CuCo2O4/CuO HCs as a promising battery-type electrode material for the next-generation advanced supercapacitors with high-performance.  相似文献   

6.
Metal‐organic frameworks (MOFs), as new class of porous materials, are constructed by inorganic metal centers and bridging organic links. Recently, MOFs have been proved to be effective templates for preparing metal oxides with large surface areas and controlled shape by directly annealing in air. There are lots of reports about metal‐organic framework‐derived metal oxides as electrode materials for supercapacitors. Metal‐organic framework‐derived metal oxides can offer higher capacitances compared with that prepared by other synthetic methods, likely attribute to high surface areas and optimal pore sizes. However, at present, the specific capacitances of MOF‐derived metal oxides received are far lower than theoretical values, and the cycle numbers could not meet practical demands. Accordingly, much effort has been made to improve the performance by further modifying MOFs. Thus, this paper focused on the advances in performance optimization of MOF‐derived metal oxide as electrode materials for supercapacitors as follows:
  1. Dual metal MOF‐derived binary metal oxides. Metal oxides with 2 metal cations possess better electrical conductivity and richer redox active sites than single metal oxides.
  2. Metal‐organic framework‐derived carbon/metal oxide composites (MO@C) or graphene/MOF‐derived graphene/metal oxide composites. Doping carbon not only facilitate transportation of electrodes but also contribution to extra double‐layer capacitance.
  3. Hybrid MOF‐derived metal oxide composites (MO@MO). Metal oxide composites can produce some synergistic effects that the individuals cannot provide.
  4. Metal‐organic framework‐derived metal oxides with a hollow structure. The Hollow structure could shorten ion diffusion distance and adapt to volume expansion generated during the ion intercalated/extracted process.
  相似文献   

7.
Controlled porosity carbons aerogels were synthesized by sol–gel polycondensation of resorcinol (R) and formaldehyde (F) using sodium-carbonate as the catalyst (C). The Effect of variation of R/C ratio and carbonization temperature on the porous structure of resultant gels and carbons was investigated by characterizing the porous structure of the materials using nitrogen adsorption–desorption measurements at 77 K. It was shown that carbons with surface areas ranging between 537 and 687 m2 g?1 and average pore size in the range of 1.80–4.62 nm can be produced when controlling the resorcinol to catalyst (R/C) molar ratio between 100 and 500 and carbonization temperature in the range of 800–1000 °C.The resultant polymeric carbons were used as the electroactive material for the fabrication of electrodes for electrochemical cells. Contact angle measurements were performed to study the wettability of the electrodes using 6 M KOH as the probing liquid. The contact angles were in the range of 106°–125° indicating the carbon based electrodes are hydrophobic in nature and no significant change in contact angles was observed with the change in R/C ratio.XRD patterns of the carbon electrodes show a typical broad peak at 2θ of about 23 indicating a disordered structure corresponding to the amorphous nature of the materials as expected for polymeric based hard carbons with crosslinked structure. These results are in line with Raman spectra of carbons which indicate two peaks in 1590 cm?1 and 1340 cm?1 wavenumber.The electrochemical performance of the electrodes was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The CV results showed that high specific capacitance of 136 Fg?1 can be achieved for the carbon with average pore diameter of 1.80 nm at a scan rate of 5 mV s?1 when using 6M KOH as the electrolyte. Electrochemical impedance (EIS) measurements also revealed that the capacitance of the cell deteriorates with increase in pore size of the carbon probably due to pore flooding by the electrolyte. The results of this study show the applicability of these carbons as potential electrode materials for supercapacitor applications.  相似文献   

8.
On the stability of TiN-based electrocatalysts for fuel cell applications   总被引:1,自引:0,他引:1  
The transition metal compound - titanium nitride (TiN), with its high electrical conductivity and corrosion resistance, can be a potential fuel cell material, particularly in the development of durable electrocatalysts replacing the state-of-the-art Pt/C. Compared to conventional carbon black, TiN nanoparticle (TiN NP) catalyst supports have a lower rate of corrosion under fuel cell conditions. The current research is a follow up study on the stability of TiN based fuel cell electrodes and its impact on the electrochemical activity of the Pt based electrocatalysts when used as an alternative to the state-of-the-art carbon black support in commercial fuel cell catalyst systems under fuel cell operating conditions. Through this paper, we report that an active behavior of TiN NP can be observed at the optimal conditions of 0.5 M H2SO4 and 60 °C. But under increased temperature or acidic conditions, the native layer on TiN tends to dissolve in the electrolyte exposing the underlying nitride surface which then gets passivated with hydroxide groups. Electrochemical and XPS characterization is used to validate our hypothesis of active or passive nature of TiN NP due to presence or absence of surface passivating -OH groups, respectively. The synthesized Pt/TiN electrocatalyst, upon subjecting to accelerated durability test, showed the performance trends which agree well with the active and passive nature of the TiN NP supports.  相似文献   

9.
Activated carbon, from biomass (pinecone), was synthesized by conventional pyrolysis/chemical activation process and utilized for the fabrication of supercapacitor electrodes. The pinecone-activated carbon synthesized with 1:4 ratio of KOH (PAC4) showed an increase in surface area and pore density with a considerable amount of oxygen functionalities on the surface. Moreover, PAC4, as supercapacitor electrode, exhibited excellent electrochemical performances with specific capacitance value ∼185 Fg−1 in 1 M H2SO4, which is higher than that of nonactivated pinecone carbon and 1:2 ratio KOH-based activated carbon (PAC2) (∼144 Fg−1). The systematic studies were performed to design various forms of devices (symmetric and asymmetric) to investigate the effect of device architecture and operating voltage on the performance and stability of the supercapacitors. The symmetric supercapacitor, designed utilizing PAC4 in H2SO4 electrolyte, exhibited a maximum device-specific capacitance of 43 Fg−1 with comparable specific energy/power and excellent stability (∼96% after 10 000 cycles). Moreover, a symmetric supercapacitor was specially designed using PAC4, as a positive electrode, and PAC2, as a negative electrode, under their electrolytic ion affinity, and which operates in aqueous Na2SO4 electrolyte for a wide cell voltage (1.8 V) and showed excellent supercapacitance performances. Also, a device was assembled with poly(3,4-ethylene dioxythiophene) (PEDOT) nanostructure, as positive electrode, and PAC4, as a negative electrode, to evaluate the feasibility of designing a hybrid supercapacitor, using polymeric nanostructure, as an electrode material along with biomass-activated carbon electrode.  相似文献   

10.
In this study, the hetero-structure of MgCo2O4 nanowires (MCO-NWs) and microcubes (MCO-MCs) on the skeleton of nickel foam (NF) was realized through a simple hydrothermal method and subsequent annealing treatment, and then served as a binder-free cathode for assembly of high-performance hybrid supercapacitor (HSC). Such synthetic methodology avoided the traditional usage of conductive and binder reagents for the electrode fabrication. The electrochemical tests indicated its battery-type characteristics, and the MCO-NWs@NF exhibited a huge specific capacity (Cs) of 389.0 C g?1 as well as 86.2% capacity retention when the current density boosted from 1 to 10 A g?1. The assembled HSC with activated carbon (AC) as anode further demonstrated the advantages of this electrode material. After 5000 cycles at 6 A g?1, the MCO-NWs@NF//AC HSC showed good long-term cycling stability without any decay in capacitance, and could deliver an energy density (Ed) of 37.9 W h kg?1 at the power density (Pd) of 958.1 W kg?1, higher than the 30.4 W h kg?1 of MCs-based HSC. These impressive results regarding electrochemical performance suggest that MCO-NWs@NF may be a promising candidate to serve as a battery-type material in electrochemical energy storage applications such as HSCs, batteries, and so on.  相似文献   

11.
In order to identify the best porous materials for the cryogenic physisorption of hydrogen, high-throughput calculations are performed starting, i.e., from the collected information in crystallographic databases. However, these calculations, like molecular simulations, require specific training and significant computational cost. Herein, a relatively simple procedure is proposed to estimate and compare hydrogen uptakes at 77 K and pressure values from 40 bar starting from the porous properties of MOF materials, without involving simulation tools. This procedure uses definitions for adsorption and considers the adsorbed phase as an incompressible fluid whose pressure-density change is that for the liquid phase at 19 K. For the 7000 structures from the CoRE MOF database, the average error of the predictions is only of 1% from reference values at 100 bar, with an SD of ±8%. This accuracy is lower than that from simulation tools, but involving lower computational cost and training.  相似文献   

12.
In this study, we synthesized a nitrogen rich compound (FPPHA) as the precursor of oxygen reduction reaction (ORR) catalysts, which was prepared based on 1,10-phenanthroline-5-amine and 2,2’-bipyridyl-5,5’-dialdehyde. The FPPHA-Fe complex was formed and be loaded on the carbon powder to form the FPPHA-Fe/C composite catalyst. The pyrolysis of the FPPHA-Fe/C composite was conducted at different temperatures, including 700 °C, 800 °C, and 900 °C, and the resultant pyrolyzed materials were designated to FPPHA-Fe/C-700, FPPHA-Fe/C-800, FPPHA-Fe/C-900, respectively. The physical characteristics of the catalysts were examined by powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller analysis, X-ray photoelectron spectrometer (XPS) and scanning electron microscopy (SEM) etc. The ORR performance of the composite catalysts were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and rotating ring disk electrodes (RRDE) in an alkaline solution. The results suggested that the pyrolysis process has a positive effect on the ORR activity of the catalysts, and among the catalysts the Fe-FPPHA/C-800 had the most preferable performance, which reduces oxygen through a predominantly four electron pathway with an average electron transfer number of 3.86 and an average hydrogen peroxide yield of 6.7%.  相似文献   

13.
A novel one step method was developed to dope nitrogen (N), sulfur (S) and carbon (C) in the Fe nanoparticles-dispersed carbon nanofibers (CNFs) grown over carbide-derived carbon (CDC), using thiourea as the single source of N, S and C. The synthesized N/S-Fe-CNF/CDC electrode was successfully used in a microbial fuel cell (MFC). When tested as the oxygen reduction reaction (ORR) catalyst, the electrode achieved a high current density (2.261 ± 0.002 mA/cm2), high OCP (0.611 ± 0.005 V), high stability upto 400 cycles, response time of ∼11 s, electron transfer number in the range 3.73–4.03, and Tafel slopes of −0.0627 and −0.183 V/dec at low and high current densities, respectively. A first order kinetics and a 4e pathway were deduced from the ORR analysis. Notably, the fabricated MFC based on the prepared electrode produced a high current density of 1.3887 ± 0.002 mA/cm2, high OCP of 0.626 ± 0.005 V and maximum power density of 0.238 ± 0.002 mW/cm2, attributed to the synergistic effects of heteroatoms, Fe nanoparticles, and CNFs.  相似文献   

14.
In this study, a nitrogen-doped 3D porous starch-derived carbon/SnO2/carbon (PSC/SnO2/C) composite is synthesized with porous starch as a carbon source by biological enzymatic hydrolysis. Compared with the traditional complex acid-base reagent method, the biological enzymatic method is more environmentally friendly and economical, and it can also naturally introduce nitrogen sources and dope the carbon layer. Many mesoporous nanostructures provide enough buffer space and promote the ions' and electrons’ transmission rate. The formation of the Sn–O–C bond between SnO2 and carbon ensures the stability of the structure. As a result, the PSC/SnO2/C composite exhibits a high initial discharge capacity (1802 mAhg−1 at 0.2 A g−1 for LIBs and 549 mAh g−1 at 0.1 A g−1 for SIBs) and good cycle stability (701 mAh g−1 at 0.2 A g−1 after 100 cycles for LIBs and 271 mAh g−1 at 0.1 A g−1 after 100 cycles for SIBs). This synthesis method can prepare other energy storage systems such as fuel cells, supercapacitors, and metal ion batteries.  相似文献   

15.
In the present work we have reported the effect of Shift heavy ion (SHI) irradiation on the gas sensing properties of tantalum (Ta)/Polyaniline (PANI) composite thin film based chemiresistor type gas sensor for hydrogen gas sensing application. PANI was synthesized chemically by in situ oxidative polymerization method. The thin sensing films of PANI were deposited onto finger type Cu-interdigited electrodes using spin cast technique and a thin Ta layer was deposited on to PANI thin film to prepare Ta/PANI composite chemiresistor sensor. These chemiresistor sensing films were irradiated with energetic Au+12 ions (150 MeV) at the different fluencies ranging from 1 × 109 to 1 × 1011 ions/cm2. The structural and morphological properties of these composite thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements before and after SHI irradiation. The electrical properties of these composite thin films were characterized by I–V characteristic measurements. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that after SHI irradiation Ta/PANI composite sensor shows a high response value and sensitivity with good repeatability in comparison to the pristine sample.  相似文献   

16.
This article reports a cheap and high yield (85%) route for synthesis of 3H-1,2-benzodithiol-3-thione (btt). Treatment of benzisothiazolinone (Hbit) with P4S10 yielded a mixture of two products which are (btt) and thiobenzisothiazolinone (Htbit). This mixture was characterized and confirmed using FT-IR, 1H-,13C- NMR, (COSY, HSQC)-2D-NMR and GC-MS. The optimal conditions for synthesis of btt in high yield and purity were investigated. The pure btt was characterized using FTIR, 1H-NMR, GC-MS, elemental analyses and thermal analyses (TG, DTG, DTA and DSC). Furthermore, the pure btt was examined for its ability in store of hydrogen and the result shows that btt is able to store 0.4611 wt% H2 under 90 bar at 77 K giving equilibrium pressure equal to 0.460 wt% H2.  相似文献   

17.
Iron/copper composite particles were synthesized by a chemical reduction method and then used as the anode material for a rechargeable alkaline battery. The particle size and structure of the samples were characterized by SEM and XRD. Their electrochemical performance was also studied. The results showed that the iron/copper composite prepared by this method is nanosized. Copper improves the electron transfer between particles, and the nanosized iron/copper composite not only has a high electrochemical capacity of up to 800 mAh g−1(Fe to Fe(III)), but also has an excellent rate-capacity performance at a current density of 3200 mA g−1. Compared with the iron nanoparticle without copper, the iron/copper composite sample maintains a smaller particle size during electrochemical cycling, and therefore improves the cycling stability of the iron electrode.  相似文献   

18.
This study evaluated the use of two types of substrates, glucose and sucrose, feeding an anaerobic fixed-bed bioreactor. The biogas produced was composed of H2 and CO2, without methane. Maximum hydrogen yields were 3.22 mol H2 mol−1 sucroseconverted and 1.51 mol H2 mol−1 glucoseconverted. The main intermediates were acetic acid, butyric acid, and ethanol. The greatest difference, however, was in the stability of the process. The operation of the reactor with sucrose exhibited a drop in biogas production, whereas operation with glucose was stable after a slight decrease in biogas production. This decrease may have been caused by the differential growth of microbial populations in each reactor, namely, the growth of organisms that use the Wood–Ljungdahl metabolic pathway.  相似文献   

19.
BaIn0.3Ti0.7O2.85 (BIT07) is a suitable electrolyte for Solid Oxide Fuel Cell (SOFC) but half cells based on La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF) as a cathode material show a degradation of the Area Specific Resistance (ASR) at 700 °C with time. This study deals with the characterization of alternative cathode materials showing a better compatibility with BIT07 than LSCF. A new solid solution, BaxLa0.58(1−x)Sr0.4(1−x)In0.3xTi0.7xCo0.2(1−x)Fe0.8(1−x)O3−δ, with 0 ≤ x ≤ 1, also called BLSITCFx, with in this case x expressed in molar %, derived from BIT07 and LSCF, has been synthesized at 1350 °C in air using BIT07 and LSCF powders. Two compositions, BLSITCF12 and BLSITCF25, have been selected due to their thermal expansion and conductivity properties. Symmetrical half cells based on these two new materials deposited on BIT07 electrolyte have been studied by complex impedance spectroscopy in air versus temperature and time. Their behaviour is comparable to LSCF's, with ASR values never exceeding 0.2 Ωcm2 at 700 °C, and moreover their less important Thermal Expansion Coefficient (TEC) mismatch with BIT07 lead to a better mechanical compatibility with time. These new compounds are therefore better candidates than LSCF as cathode materials for SOFC based on BIT07 electrolyte.  相似文献   

20.
High temperature hermetic sealants are required for the stability and good efficiency of the solid oxide fuel cells (SOFCs). Glass and glass ceramics are promising sealant materials due to their desirable properties and flexible compositions. In the present study, the novel glass series (10 + x) CaO-(10 ? x) MgO-10SrO-10B2O3-20Al2O3-40SiO2 (x = 0, 2.5, 5, 7.5) has been synthesized via melt quenching route. These glass/glass ceramics are characterized by X-ray diffraction to evaluate the amorphous nature and phase formation, respectively. The activation energy has been analyzed by using three different theoretical models – Kissinger Model, Moynihan Model and Augis and Benett Model. In addition to this, the characteristic glass temperatures and coefficient of thermal expansion (CTE) have been obtained from DTA, differential DTA (DDTA) and Dilatometry. Various stability parameters like Hruby parameter, Saad Parameter, fluctuation free volume (fg) and bulk thermal expansion coefficient (αf) are also calculated with varying CaO/MgO ratio (R). Furthermore, to analyze the stability of the glasses with varying CaO/MgO ratio over a broader range of temperature, k parameters i.e. kb (T) and kf (T) are also evaluated for different heating rates. The diffusion couples of glasses with pre oxidized Crofer 22APU and YSZ fabricated at 850 °C for 500 h have been characterized using scanning electron microscopy (SEM) and X-ray dot mapping to investigate the sealing characteristics with varying CaO/MgO ratio. The glass series 15 CaMg is very stable and promises to be a good sealant for solid oxide fuel cells.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号