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1.
Nickel oxide nanoparticles are fabricated onto graphite planes [NiO/Gt] by chemical precipitation of Ni(OH)2 particles with consecutive calcination at 400 °C. The formed electrocatalysts are characterized using X-ray diffraction (XRD) and Transmission electron microscopy (TEM). TEM images demonstrate the deposition of NiO nanoparticles on graphite surface through their crystallite lattice fringes with spacing values of 2.45 Å (111), 2.10 Å (200) and 1.48 Å (220). The electrocatalytic activity of NiO/Gt electrocatalyst is examined towards urea electro-oxidation in NaOH solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Urea oxidation peak current density is observed at NiO/Gt electrocatalyst containing 15 wt% NiO [NiO/Gt?15] at a potential value of +640 mV (Ag/AgCl) with a current density value of 17.63 mA cm?2. The loading amount of NiO in the prepared electrocatalyst significantly affects its electrocatalytic performance. NiO/Gt?15 exhibits the highest urea oxidation current density with the desired stability. The lower Tafel slope, charge transfer resistance and the higher exchange current density and diffusion coefficient values of urea molecules at NiO/Gt?15 surface elect its application as a promising electrocatalyst material during urea oxidation reaction in fuel cells.  相似文献   

2.
The difference in capacitive performance between high and low surface area RuO2 electrodes, synthesized with and without a mesoporous silica template, respectively, was investigated in aqueous solutions of sulfuric acid and sulfates by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). RuO2 synthesized with the template was crystalline and the formation of the mesoporous structure with a 6.5 nm diameter was confirmed using a transmission electron microscope and the nitrogen adsorption and desorption isotherm. From the CV at the scan rate of 1 mV s−1, the specific capacitance of the high surface area electrode in H2SO4(aq) was determined to be 200 F g−1. The high surface area RuO2 has a three times higher BET specific surface area (140 m2 g−1) than the low surface area sample (39 m2 g−1). Introducing the mesoporous structure was proved effective for increasing the capacitance per mass of the RuO2, though not all the surface functions as a capacitor. Both the CV and EIS suggest that by increasing the charging rate or frequency, the mesoporous structure of the electrode leads to a lower capacitance decrease (higher capacitance retention) than the low surface area electrode. The EIS also indicates that the response time of the capacitor is hardly influenced by the presence of the mesoporous structure.  相似文献   

3.
A facile and effective approach was developed for the preparation of mesoporous Fe-NC by pyrolyzing the mixture of FeCl2, urea, (NH4)2MoO7, phthalic anhydride and SBA-15, during which the in-situ formation of iron phthalocyanine is confirmed. The obtained catalyst exhibits high catalytic activity towards ORR, whose half-wave potential can be 53 mV more positive than that of commercial Pt/C catalyst. Besides, the catalyst also exhibits high selectivity of four electron path, along with excellent stability and methanol tolerance in alkaline media. Based on the characterization results, we suggest, the higher surface areas, highly porous structures induced by SBA-15 addition, as well as high graphitic N content should be the proper origins for its outstanding catalytic performance.  相似文献   

4.
Abstract

In the present study, aligned multiwalled carbon nanotube (MWCNT) arrays were electrodeposited with manganese oxide as electrode material for capacitor application. The electrode material was prepared in a double-stage process. The first stage, the preparation of the MWCNT array on thin nickel foils by chemical vapour deposition is well known and has already been published. This study has its focus on the second step, the electrodeposition of manganese oxide on MWCNT. Electrodeposition was performed by pulse plating of manganese oxide from a manganese acetate electrolyte. The mechanism and kinetics of this deposition process were electrochemically characterised. Additionally, the manganese oxide modified MWCNT arrays were investigated by scanning electron microscopy and Raman spectroscopy. Furthermore, the capacitor performance and the increase in the capacitance of the modified MWCNT arrays were investigated by cyclic voltammetry in a sodium sulphate electrolyte.  相似文献   

5.
To design and synthesize a noble-metal free electrocatalyst with increased efficiency and stability during urea electro-oxidation in alkaline solution is still an important challenge in the electrocatalytic field. In this work, carbon nanofibers were decorated with nickel sulphide nanoparticles [NiS@CNFs] through the electrospinning technique with subsequent heating into an argon atmosphere at 900 °C for 2 h. This formed nanomaterial was extensively characterized through X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Raman spectroscopy and N2 adsorption-desorption measurements. A conductive network of intertwined CNFs was clearly detected by FE-SEM analysis technique with varied diameters in the range of 0.6–1 μm. A highly porous nature could be suggested after incorporating NiS nanospecies resulting in increased specific surface area and valuable electrocatalytic activity for urea molecules electro-oxidation. The pore size distribution curves showed a decreased average pore diameter for NiS@CNFs nanocomposite by 2.53 folds when compared to that at CNFs. The electroactivity of NiS@CNFs nanomaterial for catalyzing urea electro-oxidation was investigated using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy measurements. Increased activity of this nanocatalyst was registered when urea molecules were added in increased concentrations into KOH solution. Lowered resistance values were also obtained describing the charge transfer process to confirm the feasibility of the studied reaction at NiS@CNFs surface. Moreover, its drawn chronoamperogram showed a stable performance during operation for long periods revealing a lowered catalytic decay. Accordingly, the aforementioned results of our fabricated nanomaterial could provide a good guide for fabricating suitable electrocatalysts for various electrocatalytic purposes.  相似文献   

6.
A high performance hemin and mesoporous carbon hybrid electrocatalyst for the oxygen reduction reaction (ORR) is developed by using hemin as the Fe–N-containing precursor to control the chemistry of the metal and the chemical composition of the carbon surface. As a first step, Hemin is used as the Fe–N-containing precursor to prepare the Fe–N-doped mesoporous carbon (H-MC) via a nano-casting process by using sucrose as a carbon source and mesoporous silica as a hard template. Hemin is then used as the Fe–N4-containing precursor to prepare H-MC supported hybrid catalyst. The Fe-doped and N-doped mesoporous carbons are also prepared and the catalytic properties of the prepared catalysts for ORR in alkaline media are investigated. The results show that as compared with the much more expensive Pt/C catalyst, the hybrid catalyst obtained in this work exhibits not only a higher onset potential, but also a higher current density.  相似文献   

7.
In this study, we present the synthesis of pristine carbon (p-CNO), nitrogen doped (N–CNO) and oxygen functionalized (ox-CNO) nano onions, using flame pyrolysis, chemical vapour deposition, and reflux methods, respectively. Pd/p-CNO, Pd/N–CNO and Pd/ox-CNO electrocatalysts are prepared using a simple and quick microwave-assisted synthesis method. The various CNO and Pd/CNO electrocatalysts are fully characterized and the FTIR and XPS results reveal that the synthesized CNOs contain oxygen and nitrogen functional groups that facilitates the attachment and dispersion of the Pd nanoparticles. Electrochemical tests show that the N–CNO and Pd/N–CNO electrocatalysts exhibit high current density (4.2 mA cm ?2 and 17.4 mA cm ?2), long-term stability (1.2 mA cm ?2 and 6.9 mA cm ?2), and fast electron transfer when compared to the equivalent pristine and oxidized catalysts (and their Pd counterparts), and a commercial Pd/C electrocatalyst, towards ethanol oxidation reactions in alkaline medium.  相似文献   

8.
Ordered mesoporous carbon (OMC) with a specific area of 570 m2 g−1 was synthesised using mesoporous silica SBA-15 as template. OMC was used as platinum catalyst support using the method of reduction with NaBH4. Before deposition of platinum, the texture and surface chemistry of the support were modified by oxidation treatments in liquid phase using nitric acid as oxidative agent. During the oxidation process, oxygen surface groups were created, whereas ordered porous structure was maintained, as temperature programmed desorption and transmission electronic microscopy showed, respectively. Platinum supported materials were well dispersed over the mesoporous support and its catalytic performance towards methanol oxidation improved when compared with commercial carbon (Vulcan XC-72).  相似文献   

9.
Vertically aligned polyaniline nanowhiskers (PANI-NWs) doped with (1R)-(−)-10-Camphorsulfonic acid (L-CSA) have been successfully synthesized on the external surface of ordered mesoporous carbon (CMK-3) by chemical oxidative polymerization. The specific surface area of the PANI-NWs/CMK-3 nanocomposite remains as high as 497 m2 g−1 by removing mesoporous silica template after the polymerization of aniline. Structural and morphological characterizations of the nanocomposite were further investigated by XRD, FTIR and FE-SEM measurements. The result shows that the nanocomposite with 40 wt% PANI applying in supercapacitor devices possesses a large specific capacitance of 470 F g−1 and good capacitance retention of 90.4% is achieved after 1000 cycles at a current density of 1.0 A g−1. The synergistic effect of small PANI nanowhisker arrays and well-ordered mesoporous carbon endows the composite with high electrochemical capacitance and good cycling stability.  相似文献   

10.
CoCr7C3-like nanorods encapsulated in carbon nanofibers shell [CoCr7C3-CNFs] were prepared using a simple electrospinning technique. The as-prepared nanocomposite was physically characterized using XRD, SEM, TEM and EDX analysis techniques. The electrocatalytic activity of CoCr7C3-CNFs was examined for methanol electro-oxidation in alkaline medium using cyclic voltammetry and chronoamperometry. The fabricated CoCr7C3-CNFs revealed good electroactivity towards methanol oxidation reaction. The measured low onset potential value [?80 mV (Ag/AgCl)] implied a marked enhancement in the oxidation kinetics at CoCr7C3-CNFs surface. Chronoamperometry test also displayed an increased steady state oxidation current density value of 18.42 mA cm?2 at 400 mV after 1800 s. This synthesized low cost, highly active and stable nanocomposite could be widely employed as a promising anode material in direct methanol fuel cells.  相似文献   

11.
A novel carbon nanostructure grown by catalytic chemical vapour deposition technique has been applied as an electrocatalyst support for oxygen reduction reaction in proton exchange membrane fuel cell. The growth of carbon nanostructure (CNS) is carried over a low cost bi-metal oxide catalyst (Fe–Sn–O) synthesized by sol–gel technique. Platinum nanoparticle decoration on Fe–Sn–O incorporated CNS (CNS-FSO) is performed by ethylene glycol reduction method. The structural as well as morphological analysis confirms the formation of CNS-FSO and platinum decoration on CNS-FSO. The electrochemically active surface area (ECSA) of platinum decorated CNS-FSO (Pt/CNS-FSO) is 68 m2 g−1, as revealed from cyclic voltammetry. Polarization studies are carried out at different temperatures (40 °C, 50 °C and 60 °C) to exploit the oxygen reduction reaction activity of Pt/CNS-FSO. A maximum power density of 449 mW cm−2 (without back pressure) at 60 °C shows the potential of this novel CNS-FSO as an electrocatalyst support in proton exchange membrane fuel cell.  相似文献   

12.
We report on the synthesis and application of an inexpensive pyridine-based additive allyl isonicotinate (AIN) for the efficient dye-sensitized solar cells (DSCs). AIN can be quickly synthesized at room temperature without any solvent. The presence of AIN in the electrolyte enhances the open-circuit voltage (Voc), fill factor (FF) and short-circuit photocurrent (Jsc), consequently improving the energy conversion efficiency (η) from 6.5% to 8.2%. The impedance experiments show that the adsorption of AIN leads to the negative shift of the conduction band edge of the dye-sensitized TiO2 around 55 mV. The presence of AIN in the electrolyte can obviously suppress the recombination of the injected electrons, increasing the lifetime of electrons in the TiO2. The negative shift of the conduction band edge and the suppression of the recombination of the injected electrons contribute to the higher power conversion efficiency.  相似文献   

13.
Mesoporous carbon microspheres (MCMs) with the diameters of 0.5-2.0 μm, main mesopore sizes of 2.6-4.0 nm and specific surface areas of 449-1212 m2 g−1 are synthesized by a novel hydrothermal emulsion-activated method. The typical MCMs as electrode materials have a specific capacitance of 157 F g−1 at a high current density of 10.0 A g−1 in 6 M KOH aqueous solution. The resultant MCMs electrode materials with high current charge and discharge capability in 6 M KOH aqueous solution provide important prospect for electrode materials in supercapacitors which could offer high power density for electric vehicles.  相似文献   

14.
Electrochemical water splitting has gained momentum for the development of alternative energy sources. Herein, we report the synthesis of two different nickel selenide nanostructures of different morphology and composition employing hydrothermal method. NiSe2 nanosheets were obtained by the anion-exchange reaction of Ni(OH)2 with Se ions for 15 h. On the other hand, NiSe nanoflakes were synthesized by the direct selenization of nickel surface with the reaction time of 2 h. Tested as an electrocatalyst for hydrogen evolution reaction, NiSe2 nanosheets and NiSe nanoflakes can afford a geometric current density of 10 mA cm?2 at an overpotential of 198 mV and 217 mV respectively. The measured Tafel slope values of NiSe nanoflakes are 28.6 mV dec?1, which is three times lower as compared with NiSe2 nanosheets (72.1 mV dec?1). These results indicates the HER kinetics of NiSe nanoflakes are at par with the state-of-the-art Pt/C catalyst and also complimented with the short synthesis time of 2 h. Further, both nickel selenides exhibit ultra-long term stability for 30 h as evident from constant current chronopotentiometry and electrochemical impedance spectroscopy results.  相似文献   

15.
The performance of membrane electrode assembly (MEA) prepared with PtRu nanoparticles supported on a mesoporous carbon as anode catalyst are presented and compared against PtRu synthesized over Vulcan carbon. Polarization and power curves were obtained using 1 M methanol aqueous solution at the anode and O2 at the cathode. The mesoporous carbon supported catalyst shows peak power of 40 mW cm−2 and 67 mW cm−2 at 30 °C and 60 °C respectively, that is, 15–30% higher than the Vulcan supported catalyst, and exhibits a wider range of operating current. Moreover, an improvement in the mass transport is observed for the catalyst supported on mesoporous carbon, yielding a lower voltage drop at high current density. This behavior was confirmed by electrochemical impedance spectroscopy (EIS), where an increases of the Warburg coefficient value by a factor 3–4 for the catalyst supported on mesoporous carbon as compared with that supported on Vulcan, would indicate a more facile diffusion of methanol through the mesoporous carbon.  相似文献   

16.
We demonstrate Pd nanoparticles on well-defined mesoporous tungsten carbide (Pd/meso-WC) for methanol electrooxidation in alkaline solution. The meso-WC exhibits mesoporous structure with ∼8.5 nm in average pore size and ∼47 m2 g−1 in specific surface area. The Pd nanoparticles with size of ∼3.3 nm are highly dispersed on the meso-WC. The electron transfer from W to Pd due to the difference of electronegativity is confirmed by X-ray photoelectron spectroscopy. The improved electrocatalytic activity and stability for methanol electrooxidation of Pd/meso-WC is likely to be mainly attributed to a strong interaction between Pd nanoparticles and mesoporous tungsten carbide structure.  相似文献   

17.
To engineering high-efficient, sustainable and novel Pt-based composite system, a newly “Pt-oxide” based composites electrocatalyst of “CeO2 overlapped with nitrogen-doped carbon layer anchoring Pt nanoparticles” (PtCeO2@CN) has been fabricated. In comparison with Pt/C, the results exhibit that PtCeO2@CN possesses a preferable methanol tolerance ability, superior stability (30000 s degradation: 35% for PtCeO2@CN vs. 50% for Pt/C), and more positively the onset potential (16 mV) as well as half-wave potential (29 mV) towards oxygen reduction reaction. Further, the investigation shows that PtCeO2@CN has a certain selectivity with quasi-four electron pathway (n = 3.2–3.3 e?). This is attributed to the establishment of “nitrogen-doped carbon layer” structure, which heightens the conductivity of CeO2, further promotes electron transfer between Pt and CeO2, as well as strengthens the anchoring effect for Pt nanoparticles. Overall, this study would shed bright light to develop some effective Pt-oxide based composite electrocatalysts.  相似文献   

18.
This article reports two routes, microwave-assisted synthesis and thermal reduction, to deposit silver nanoparticles on oxidized carbon paper (CP) electrodes. In comparison, as-grown Ag particles, prepared by the microwave-assisted route, exhibit uniform particle size and well-dispersion over the CP substrate. Electrochemical behavior of Ag-CP electrodes is characterized by cyclic voltammetry and AC impedance spectroscopy, incorporated with equivalent circuit. Both the catalyst electrodes display redox reversibility within the potential region of 0-0.5 V vs. saturated calomel electrode (SCE) in 1 M NaOH. According to the Randles-Sevcik plot, the diffusion coefficient under voltammetric regime ranges from 9.06 × 10−10 to 3.33 × 10−10 cm2 s−1. These differences of diffusion coefficient and capacitance are ascribed to the resulting Ag nanocatalysts with small particle size and no aggregation. On the basis of the results, the microwave-assisted approach for depositing nano sized Ag catalysts on CP electrodes shows the potential in application of alkaline fuel cells because of its fast synthesis, high activity, and simplicity.  相似文献   

19.
A colloidal silica incorporated porous anodic aluminum oxide (AAO) was utilized as a dual-template to prepare mesoporous carbon nanofibers (MCNFs). Such a strategy is simple because it takes advantage of commercially available materials (i.e., colloidal silica and AAO) and the templates can be removed in one step. The as-prepared MCNF shows a hierarchical nanostructure consisting of open macroporous channel connected with large mesopores and micropores. As a result of the large surface area and unique hierarchical nanoarchitecture which facilitates fast mass and electron transport, the MCNF reveals a discharge capacity of 679 mA h g−1 at 25 mA g−1. This value is significantly greater than that (i.e., 394 mA h g−1) observed for an ordered mesoporous carbon (OMC) with a similar specific surface area. Furthermore, at 3000 mA g−1, the MCNF demonstrates a discharge capacity of 585 mA h g−1, which is about twice that (i.e., 256 mA h g−1) of the OMC.  相似文献   

20.
A single PEMFC has been operated by varying the assembly temperature, the air dew point temperature and the anode/cathode stoichiometry rates with the aim to identify the parameters and combinations of factors affecting the cell performance. Some of the experiments were conducted with low humidified reactants (relative humidity of 12%). The FC characterizations tests have been conducted using in situ electrochemical methods based on load current and cell voltage signal analysis, namely: polarization curves, EIS measurements, cyclic and linear sweep voltammetries (CV and LSV). The impacts of the parameters on the global FC performances were observed using the polarization curves whereas EIS, CV and LSV test results were used to discriminate the different voltage loss sources. The test results suggest that some parameter sets allow maximal output voltages but can also induce material degradation. For instance, higher FC temperature and air flow values can induce significant electrical efficiency benefits, notably by increasing the reversible potential and the reaction kinetics. However, raising the cell temperature can also gradually dry the FC and increase the risk of membrane failure. LSV has also shown that elevated FC temperature and relative humidity can also accelerate the electrolyte degradation (i.e. slightly higher fuel crossover rate) and reduce the lifetime consequently.  相似文献   

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