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1.
A new approach based on stepwise oxidation of o-anisidine is explored for generating nanoporous films of poly(o-anisidine), POA and loading of Pt nanoparticles that are subsequently used for electrocatalysis of methanol oxidation are presented and compared with bulk Pt. POA film can easily be prepared by stepwise electro-oxidation procedure with very high porosity consisting of nanofibrillar structure using without templates. Controlled sizes of Pt nanoparticles were entrapped into POA matrix by a two-step process in which first PtCl62− ions are sorbed into the pores of polymer matrix followed by electroreduction at −0.55 V in a 0.5 M H2SO4 solution. Loading of Pt nanoparticles (10-200 μg/cm2) onto POA matrix were accomplished by varying the concentration (2-10 mM) of the sorbate, i.e., H2PtCl6. The sizes of the Pt nanoparticles were determined from TEM analysis and Pt particles were found to be in the range of 10-20 nm. The crystallite phase of Pt particles in POA was examined from XRD pattern. AFM image further supports Pt particles embedded in POA matrix.  相似文献   

2.
Gang Wu 《Carbon》2005,43(12):2579-2587
Vulcan XC-72 carbon black particles (average size: ca. 50 nm) was incorporated into polyaniline (PANI) matrix by an electrochemical codeposition technique during the electropolymerization process. The doping by carbon particles leads to a higher polymeric degree and a lower defect density in the PANI structure. Furthermore, the incorporation of carbon particles not only increases the electrochemical accessible surface areas (Sa) and electron conductivity of the PANI film, but also decreases charge transfer resistance at PANI/electrolyte interfaces. Therefore, as expected, a fabricated PANI + C composite film with dispersed Pt and PtRu particles exhibited excellent electrocatalytic activity for methanol oxidation due to better Pt dispersion and utilization. The PANI + C composite film is more promising as a support material in electrocatalysis than a PANI film. Meanwhile, a new application for regular carbon black as a doping material into conducting polymer for electrocatalysis was thus demonstrated.  相似文献   

3.
Liang Ding 《Electrochimica acta》2010,55(28):8471-8475
The electrocatalytic reduction of bromate ion (BrO3) was investigated in a three-electrode system using polyaniline (PANI) as the electrode material. Bromate ion reduction and Br removal were observed during electrochemical treatment because of the catalytic and doping capabilities of the PANI film. BrO3 removal efficiency in the 0.10 mol L−1 Na2SO4 supporting electrolyte achieved 99% at pH 7 in 25 min, with no bromide ion detected in the solution. Optimal removal was found in pH range 6-7, and the pH of the solution had a significant impact on bromate reduction. A reduction mechanism was also discussed by analyzing the cyclic voltammograms of the reduction process and X-ray photoelectron spectra of the main elements (N 1s and Br 3d) on the PANI surface. We propose that during the electrocatalytic reduction process, bromate is reduced to bromide because of the loss of electrons from the nitrogen atoms on the PANI chains. The doping of the resultant Br ions in the PANI film has an important role in avoiding further oxidation of Br to BrO3. The used PANI film can be regenerated by de-doping the Br ions with a 0.5 mol L−1 H2SO4 solution. Thus the process can be considered efficient and green.  相似文献   

4.
The electrochemical and adsorptive behavior of formaldehyde at Pt electrodes in acidic media was investigated using cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) techniques. All chemical and electrochemical steps related to formaldehyde oxidation (e.g. bulk adsorption and oxidation, CO (sub)monolayer adsorption and oxidation and electrons per Pt site) were analyzed. All the mass and charge density data in this paper are referred to the real surface area. The charge density associated with formaldehyde oxidation was close to 420 μC cm−2, which is related to the oxidation of approximately one CO monolayer with two electrons transferred. For CO adsorption the experimental mass value was 50 ng cm−2. In the region of CO oxidation the analysis of mass and charge variations indicates simultaneous CO oxidation, anion and water adsorption and CO readsorption. The mechanism was confirmed by CO and CO2 flux calculations. From the analysis of the mass-charge ratio and species flux it was concluded that CO, an intermediate produced during formaldehyde oxidation, is adsorbed at the Pt surface and the main contribution to the mass increase during formaldehyde oxidation is CO readsorption, and water adsorption.  相似文献   

5.
The controlled uptake and electrochemical reduction of metal precursors PdCl42− and PdCl62− in polyaniline (PANI) is demonstrated. The formation of PANI/Pd composites is achieved with a reduction in proton doping and an increase in the oxidation of the polymer with Pd deposits physically blocking the nitrogen groups. High surface area filaments (PdCl42−) or a rough encapsulation (PdCl62−) of Pd metal on PANI are obtained. The structural differences highlight the influence of the metal precursor oxidation state on the morphology of the Pd deposits in PANI. Thermal gravimetric analysis provides an estimate of the Pd content for each composite of ∼40%. X-ray Photoelectron Spectroscopy and X-ray-excited Auger Electron Spectroscopy analyses confirm the deposition of Pd metal. The catalytic oxidation of methanol was demonstrated for both PANI/Pd composites in alkaline solutions that prohibit proton doping of the polymer. The data indicates that Pd metal acts as a solid-state dopant that may delocalize the charge on the polymer backbone to maintain conductivity. Methanol oxidation at PANI/Pd composites produced using PdCl42− was enhanced relative to the composite produced using PdCl62− and a planar Pd electrode. Comparison of PANI/Pd composite produced using PdCl42− with other Pd catalysts from the literature indicates surface poisoning is reduced when Pd is coupled with the polymer. The composite is robust and stable in alkaline solution with the charge density decreasing by 5% on the positive scan and 13% on the negative scan after 200 voltammetric cycles. The data also indicates that the reductive desorption of surface contaminants is possible, minimizing the catalytic loss due to surface poisoning.  相似文献   

6.
The solid-state method was applied for synthesizing polyaniline (PANI)/noble metal hybrid materials with the presence of HAuCl4·4H2O or H2PtCl6·6H2O in the reaction medium. The structure, morphology, and electrochemical activity of the composites were characterized by Fourier transform infrared (FTIR) spectra, UV-visible (vis) absorption spectra, energy dispersive spectrum (EDS), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cyclic voltammetry. The results from FTIR and UV-vis spectra showed that the oxidation degree and doping level of the PANI in composites can be influenced by HAuCl4·4H2O and H2PtCl6·6H2O. The EDS data demonstrated that the composites contain a certain amount of Au (or Pt) element. XRD analysis indicated the presence of crystalline-state Au particles in PANI matrix prepared from the presence of HAuCl4·4H2O and revealed that the H2PtCl6·6H2O cannot be converted into metal Pt. The TEM and SEM images implied that the Au particles did exist in the polymer matrix with the size of about 20 nm. The enzymeless H2O2 sensor constructed with PANI/Au composite from the presence of HAuCl4·4H2O showed a short response time (within 5 s) and displayed an excellent performance in wide linear range.  相似文献   

7.
The electrosynthesis of polyaniline on the bare aluminum and pre-treated aluminum surface achieved in aqueous H2PtCl6 solution saturated with NaF for few seconds is described. The effect of some factors such as pre-treatment time, aniline and sulfuric acid concentrations on the electropolymerization process was investigated and optimum conditions were obtained. The stability of polyaniline film on the pre-treated aluminum electrode (Al-Pt) was studied as function of the potential imposed on the electrode. For applied electrode potentials of 0.1-0.7 V, the first-order degradation rate constant, k, of polyaniline film varies between 1 × 10−6 and 2 × 10−5 s−1, and a relatively low slope (i.e. 2.1) was obtained for the plot of log k versus E. The coatings were characterized by scanning electron microscopy (SEM), and cyclic voltammetric behavior of the polyaniline-deposited Al electrode (Al/PANI) and polyaniline-deposited Al-Pt electrode (Al-Pt/PANI) in 0.1 H2SO4 solutions is described. The electrocatalytic activity of the Al-Pt/PANI electrode against para-benzoquinone/hydroquinone (Q/H2Q) and Fe(CN)63−/Fe(CN)64− redox systems was investigated and the obtained results are compared with those obtained on Al/PANI and bulk Pt electrodes.  相似文献   

8.
Pt counter electrodes (CEs) with different platinum loading have been prepared using chemical reduced method on flexible indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) for dye-sensitized solar cells (DSSCs). H2PtCl6·6H2O terpineol solutions were screen printed on the transparent ITO-PEN substrates. After drying, H2PtCl6 was reduced by treating it in NaBH4 solution followed by the hydrothermal treatment at 100 °C. The obtained Pt CEs with different Pt-loading (2.4-7.7 μg/cm2) were characterized by SEM, XPS, electrochemical impedance and transmission spectrum measurement. The Pt CEs show high catalytic activity, low charge transfer resistance (0.26-1.38 Ω cm2) and good light transmittance (about 70% at 400-800 nm). The light-to-electricity conversion efficiency of the flexible DSSC fabricated with the prepared Pt CE and the TiO2 photoanode prepared on Ti substrate by screen printing technique attains 5.41% under the simulated AM 1.5 sunlight, which is almost same as that based on the thermal decomposited Pt CE on FTO-glass. Compared with other methods to prepare Pt CEs, chemical reduced method is simple and suitable for flexible polymer substrates and the large scale preparation of DSSCs.  相似文献   

9.
Polyacrylonitrile nanofibrous mats coated with continuous thin gold films (Au-PAN) have been fabricated by combining the electrospinning and electroless plating techniques. The Pt particles are electrodeposited on the Au-PAN fibers surface by multi-cycle CV method, and the Au-PAN decorated with Pt (Pt/Au-PAN) shows higher activity toward methanol electro-oxidation. The catalytic peak current for methanol oxidation on the optimum Pt/Au-PAN electrode can reach about 450 mA mg−1 Pt which is much larger than the catalytic peak current for methanol oxidation (118.4 mA mg−1 Pt) on the electrode prepared by loading commercial Pt/C on Au-PAN (Pt/C/Au-PAN). Further experiments reveal that the Pt/Au-PAN electrodes exhibit better stability and smaller charge transfer resistance than Pt/C/Au-PAN electrodes, which indicates that the Au-PAN may be developed as supporting material for catalyst. The microscopy images of the electrodes show that the Pt particles deposited on Au-PAN conglomerate into larger particles, and that the Pt/C catalyst loaded on the Au-PAN also exhibits conglomeration after stability test. The hydrogen adsorption-desorption experiments indicate that the electrochemical surface area of the Pt particles for the both kinds of electrodes has decreased after stability test.  相似文献   

10.
Lu Yuan  Ruqin Yu 《Electrochimica acta》2008,53(10):3559-3565
Platinum nanoparticles (PtNPs) were prepared by seed-mediated growth method with Au nanoparticles (AuNPs) playing the role of seeds. Carbon nanotubes (CNTs) and AuNPs were first dropped onto the surface of glassy carbon (GC) electrode, and then the electrode was immersed into growth solution which contains H2PtCl6 and ascorbic acid. PtNPs were successfully grown onto the CNT surface due to the chemical reduction of Pt(IV). The electrode modified with AuNPseed/PtNP/CNT film displayed excellent electrochemical response to H2O2 at 0.45 V versus saturated calomel electrode (SCE) with sensitivity much larger than that of PtNP/CNT and AuNPseed/PtNP modified electrodes. Glucose oxidase was selected as a model enzyme and electrodeposited onto the AuNPseed/PtNP/CNT modified electrode in the presence of a detergent. The resulting biosensor enabled selective determination of glucose with high sensitivity of 4.49 μA mM−1, quick response time about 2 s, low-detection limit of 0.5 μM and wide linear range from 1 μM to 4 mM with a correlation coefficient 0.9998. Thus, the modified electrode proved to be a nice electrochemical biosensing platform for the fabrication of oxidase-based biosensors.  相似文献   

11.
A new amperometric glucose biosensor has been developed based on platinum (Pt) nanoparticles/polymerized ionic liquid-carbon nanotubes (CNTs) nanocomposites (PtNPs/PIL-CNTs). The CNTs was functionalized with polymerized ionic liquid (PIL) through directly polymerization of the ionic liquid, 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM]BF4), on carbon nanotubes and then used as the support for the highly dispersed Pt nanoparticles. The electrochemical performance of the PtNPs/PIL-CNTs modified glassy carbon (PtNPs/PIL-CNTs/GC) electrode has been investigated by typical electrochemical methods. The PtNPs/PIL-CNTs/GC electrode shows high electrocatalytic activity towards the oxidation of hydrogen peroxide. Taking glucose oxidase (GOD) as the model, the resulting amperometric glucose biosensor shows good analytical characteristics, such as a high sensitivity (28.28 μA mM−1 cm−2), wide linear range (up to 12 mM) and low detection limit (10 μM).  相似文献   

12.
Aniline doped with polyvinyl sulphonate (PV-SO3) was electropolymerised on screen printed carbon (SPCE) and glassy carbon (GCE) electrodes. Then nano-structured polystyrene (PSNP) latex beads functionalised with amine (PSNP-NH2) and sulphate (PSNP-OSO3) were self-assembled on the modified SPCE and GCE. The resultant polyaniline nanocomposites (PANI|PSNP-NH2 or PANI|PSNP-OSO3) were characterised by cyclic voltammetry (CV), UV-vis spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations of the order of 10−8 mol cm−2. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid π-π* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that are <100 nm in diameter. When applied as electrochemical nitrite sensor, sensitivity values of 60, 40 and 30 μA/mM were obtained for electrode systems containing PANI|PSNP-NH2, PANI and PANI|PSNP-SO3, respectively. The corresponding limits of detection of the sensors were 7.4, 9.2 and 38.2 μM NO2.  相似文献   

13.
A novel electrically conducting polymer consisting of selenophene moiety, poly(biselenophene) (PBSE) was generated by chemical and electrochemical polymerization. This polymer gave lower bandgap energy (1.9 eV) than pristine polyselenophene (2.0 eV). The electrochemical and optical properties of PBSE was investigated by UV-Vis near infrared spectroscopy and electrochemistry. In situ electrochemical doping studies of PBSE showed the formation of polaron states at 1.4 and 0.8 eV. Through cyclic voltammetry, the polymer oxidation potential (Epa) and reduction potential (Epc) for p-doping process for PBSE were observed at 0.93 and 0.86 V, respectively, at a scan rate of 20 mV s−1. Upon chemical doping using chemical reagents such as iodine and ferric chloride, a maximum conductivity of 0.1 S cm−1 was achieved.  相似文献   

14.
An electrochemical impedance analysis of the doping kinetics of polydicarbazole films is reported. Polymer films of varying thickness were analyzed using an impedance model that considers spatially-restricted diffusion of ionic species. The main bulk parameters for diffusion and charge accumulation during doping were determined from fits. These parameters resulted independent of film thickness after considering the experimental error. The equilibrium (bulk) capacitance C0 varies in the range of 100-800 F cm−3. The chemical diffusion coefficient D varies within the range of 10−10 to 10−8 cm2 s−1 and increases as the steady-state potential reaches the oxidation peak potential.  相似文献   

15.
The electrochemical oxidation of BH4 in 2 M NaOH on Pt and Au (i.e. catalytic and non-catalytic electrodes, respectively, for BH4 hydrolysis accompanied by H2 evolution) has been studied by cyclic voltammetry, chrono-techniques (i.e., potentiometry, amperometry, coulometry) and electrochemical impedance spectroscopy. In the case of Pt the cyclic voltammetry behaviour of BH4 is influenced by both, the catalytic hydrolysis of BH4 yielding H2 (followed by electrooxidation of the latter at peak potentials between −0.7 and −0.9 V versus Ag/AgCl, KClstd) and direct oxidation of BH4 at more positive potentials, i.e., between −0.15 and −0.05 V. Thiourea (TU, 1.5×10−3 M) was an effective inhibitor of the catalytic hydrolysis associated with BH4 electrooxidation on Pt. Therefore, in the presence of TU, only the direct oxidation of BH4 has been detected, with peak potentials between −0.2 and 0 V. It is proposed that TU could improve the BH4 utilization efficiency and the coulombic efficiency of direct borohydride fuel cells using catalytic anodes. The electrooxidation of BH4 on Pt/TU is an overall four-electron process, instead of the maximum eight electrons reported for Au, and it is affected by adsorbed species such as BH4 (fractional surface coverage ∼0.3), TU and possibly reaction intermediates.  相似文献   

16.
We report the electrochemical formation of Pt particles on fluorine-doped tin oxide electrodes by varying the concentration of PtCl42− ions and the overpotentials within the mass-transfer-limited region. The nucleation mechanisms are considered based on the results obtained by cyclic voltammetry, chronoamperometry, and scanning electron microscopy; the nucleation mechanism changes from progressive to instantaneous as the overpotential and the concentration increase. The physical properties of deposited Pt particles, such as particle density, size, and morphology, are also studied with the changes in overpotential, concentration of PtCl42− ions, or both.  相似文献   

17.
Yunzhen Chang  Gaoyi Han  Miaoyu Li  Fei Gao 《Carbon》2011,49(15):5158-5165
Graphene-modified carbon fiber mats (GCFMs) with high conductivity of about 65 S cm−1 and good flexibility have been fabricated by thermally treating electrospun polyacrylonitrile fibers decorated with graphene oxide. Pt particles were then deposited on the GCFM by using formaldehyde vapor as a reducer to react with H2PtCl6·6H2O adsorbed on the GCFM. The obtained electro-catalytic electrodes were characterized and evaluated. The results show that the Pt catalyst loaded on GCFM exhibits high electro-catalytic activity, good tolerance towards reaction intermediates and unusually high stability towards methanol electrochemical oxidation because the special structure of GCFM can stabilize the Pt particles, and that the charge transfer resistance between the methanol and the catalytic electrode is as small as 15.7 Ωcm2. An electrochemical catalyst with high activity and stability can be developed by using GCFM as a supporting material.  相似文献   

18.
Degradation of Disperse Orange 1, Disperse Red 1 and Disperse Red 13 dyes has been performed using electrochemical oxidation on Pt electrode, chemical chlorination and photoelectrochemical oxidation on Ti/TiO2 thin film electrodes in NaCl or Na2SO4 medium. 100% discoloration was obtained for all tested methods after 1 h of treatment. Faster color removal was obtained by photoelectrocatalytic oxidation in 0.1 mol L−1 NaCl pH 4.0 under UV light and an applied potential of +1.0 V (vs SCE reference electrode), which indicates also values around 60% of TOC removal. The conventional chlorination method and electrochemical oxidation on Pt electrode resulted in negligible reduction of TOC removal. All dyes showed positive mutagenic activity in the Salmonella/microsome assay with the strain TA98 in the absence and presence of S9 (exogenous metabolic activation). Nevertheless, there is complete reduction of the mutagenic activity after 1 h of photoelectrocatalytic oxidation, suggesting that this process would be good option to remove disperse azo dyes from aqueous media.  相似文献   

19.
An anhydrous proton conductor, Sn0.95Al0.05P2O7 (SAPO), composed of polystyrene-b-poly(ethylene/propylene)-b-polystyrene (SEPS), was developed and characterized using morphological, structural, and electrochemical analyses. In the composite membrane with 20 wt% SEPS, a homogeneous distribution of SAPO particles in the matrix was obtained in the thickness range of 65-90 μm, yielding a proton conductivity of 3.4 × 10−3 S cm−1 at 200 °C, tensile strength of 4.6 MPa and an elongation at break of 711.0% at room temperature. Fuel cell tests verified that the open-circuit voltage was maintained at a constant value of approximately 1 V between 100 and 250 °C. The peak power densities achieved with unhumidified H2 and air were 77.0 mW cm−2 at 100 °C, 121.0 mW cm−2 at 150 °C, and 163.1 mW cm−2 at 225 °C.  相似文献   

20.
Makoto Togo 《Electrochimica acta》2007,52(14):4669-4674
Viamin K3-modified poly-l-lysine (PLL-VK3) was synthesized and used as the electron transfer mediator during catalytic oxidation of NADH by diaphorase (Dp) at the anode of biofuel cell. PLL-VK3 and Dp were co-immobilized on an electrode and then coated with NAD+-dependent glucose dehydrogenase (GDH). The resulting enzymatic bilayer (abbreviated PLL-VK3/Dp/GDH) catalyzed glucose oxidation. Addition of carbon black (Ketjenblack, KB) into the bilayer enlarged the effective surface area of the electrode and consequentially increased the catalytic activity. An oxidation current of ca. 2 mA cm−2 was observed when the electrochemical cell contained a stirred 30 mM glucose, 1.0 mM NAD+, pH 7.0 phosphate-buffered electrolyte solution. The performance of glucose/O2 biofuel cells, constructed as fluidic chips with controllable fuel flow and containing a KB/PLL-VK3/Dp/GDH-coated anode and an Ag/AgCl or a polydimethylsiloxane-coated Pt cathode, were evaluated. The open circuit voltage of the cell with the PDMS-coated Pt cathode was 0.55 V and its maximum power density was 32 μW cm−2 at 0.29 V when a pH 7.0-buffered fuel containing 5.0 mM glucose and 1.0 mM NAD+ was introduced into the cell at a flow rate of 1.0 mL min−1. The cell's output increased as the flow rate increased. During 18 h of continuous operation of the cell with a load of 100 kΩ, the output current density declined by ca. 50%, probably due to swelling of the enzyme bilayer.  相似文献   

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