共查询到20条相似文献,搜索用时 15 毫秒
1.
Agnieszka Kapa?ka 《Electrochimica acta》2007,53(4):1954-1961
In this paper, the electrochemical oxygen transfer reaction (EOTR) is studied on boron-doped diamond electrodes using simple C1 organic compounds (methanol and formic acid). The kinetics of both oxygen evolution (side reaction) and organics oxidation (main reaction) has been investigated using boron-doped diamond microelectrodes-array (BDD MEA). Oxygen evolution, in the high-potential region, takes place with a Tafel slope of 120 mV dec−1 and zero reaction order with respect to H+. In the presence of organics, a shift of the polarization curves to lower potentials is observed while the Tafel slopes remain close to 120 mV dec−1. A simplified model of C1 organics oxidation is proposed. Both water discharge and organics oxidation are assumed to be fast reactions. The slowest step of the studied EOTR is the anodic discharge of hydroxyl radicals to oxygen. Further in this work, electrolysis of formic acid on boron-doped diamond macroelectrode is presented. In order to achieve 100% current efficiency, electrolysis was carried out under programmed current, in which the current density was adjusted to the limiting value. 相似文献
2.
Takeshi Kondo Hiroyuki Ito Kazuhiro Ohkawa Akira Fujishima Takeshi Kawai 《Electrochimica acta》2007,52(11):3841-3848
Boron-doped diamond (BDD) thin film surfaces were modified by brief plasma treatment using various source gases such as Cl2, CF4, Ar and CH4, and the electrochemical properties of the surfaces were subsequently investigated. From X-ray photoelectron spectroscopy analysis, Cl and F atoms were detected on the BDD surfaces after 3 min of Cl2 and CF4 plasma treatments, respectively. From the results of cyclic voltammetry and electrochemical AC impedance measurements, the electron-transfer rate for Fe(CN)63−/4− and Fe2+/3+ at the BDD electrodes was found to decrease after Cl2 and CF4 plasma treatments. However, the electron-transfer rate for Ru(NH3)62+/3+ showed almost no change after these treatments. This may have been related to the specific interactions of surface halogen (C-Cl and C-F) moieties with the redox species because no electrical passivation was observed after the treatments. In addition, Raman spectroscopy showed that CH4 plasma treatment of diamond surfaces formed an insulating diamond-like carbon thin layer on the surfaces. Thus, by an appropriate choice of plasma source, short-duration plasma treatments can be an effective way to functionalize diamond surfaces in various ways while maintaining a wide potential window and a low background current. 相似文献
3.
Electrochemical treatment of wastewater containing phenolic compounds: oxidation at boron-doped diamond electrodes 总被引:4,自引:0,他引:4
This work investigates the performance of BDD electrodes during oxidation of aqueous solutions of phenol. The main reaction intermediates are identified, the effect of operating conditions on the faradic yield of the process, and the degree of mineralization achievable under different experimental conditions are evaluated. Due to the crucial role of mass transfer in the process, an impinging jet cell is used for the experiments. The results indicate that if a minimum value of current density is imposed, suitable initial conditions can be set at which the removal of the reactant is always under mass transfer control and the process is carried out at a faradic yield of about unity, up to the near-complete disappearance of total organic load. High current density and high mass transfer coefficient must be used in order to carry out the process with high space-time yield. The performance of BDD is compared to that obtained at Ti/RuO2 anodes. 相似文献
4.
Joanna Niedzió?ka-Jönsson Susan Boland Rabah Boukherroub Sabine Szunerits 《Electrochimica acta》2010,55(3):959-964
The paper reports on the formation of carboxy-terminated boron-doped diamond (BDD) electrodes. The carboxylic acid termination was prepared in a controlled way by reacting photochemically oxidized BDD with succinic anhydride. The resulting interface was readily employed for the linking of an amine-terminated ligand such as an osmium complex bearing an amine terminal group. The interfaces were characterized using X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Contact angle measurements were used to follow the changes in surface wetting properties due to surface functionalization. The chemical reactivity of the carboxyl-terminated BDD was investigated by covalent coupling of the acid groups to an amine-terminated osmium complex. 相似文献
5.
The synthesis, physical characterization, decontamination and some electrocatalytic properties of PtRu nanoparticles prepared using the microemulsion method are reported. The nanoparticles are synthesized by reduction with sodium borohydride of H2PtCl6 and RuCl3 in a water-in-oil microemulsion of water/polyethylenglycol-dodecylether (BRIJ® 30)/n-heptane. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive analysis by X-rays (EDAX) experiments were carried out to characterize the single and bimetallic nanoparticles obtained. Cyclic voltammograms (CV) of clean nanoparticles were obtained after a controlled decontamination procedure of their surfaces. CO adsorption–oxidation and methanol electrooxidation were used as test reactions to check the electrocatalytic behaviour of the bimetallic nanoparticles. Pt80Ru20 (nominal atomic composition) nanoparticles are the best electrocatalyst for both COad and methanol oxidation. All these results show that the microemulsion method can be used to produce bimetallic nanoparticles in a very easy way. The method can be very easily scaled-up for industrial use. 相似文献
6.
Oxidation of carboxylic acids at boron-doped diamond electrodes for wastewater treatment 总被引:11,自引:0,他引:11
D. Gandini E. Mahé P.A. Michaud W. Haenni A. Perret Ch. Comninellis 《Journal of Applied Electrochemistry》2000,30(12):1345-1350
Thin boron-doped diamond films have been prepared by HF CVD (hot filament chemical vapour deposition technique) on conductive p-Si substrate (Si/Diamond). The morphology of these Si/diamond electrodes has been investigated by SEM and Raman spectroscopy. The electrochemical behaviour of the Si/diamond electrodes in 1 M H2SO4 and in 1 M H2SO4 + carboxylic acids has been investigated by cyclic voltammetry. Finally, the electrochemical oxidation of some simple carboxylic acids (acetic, formic, oxalic) has been investigated by bulk electrolysis. These acids can be oxidized at Si/diamond anodes to CO2, in the potential region of water and/or the supporting electrolyte decomposition, with high current efficiency. 相似文献
7.
The principle of the intermittent microwave heating (IMH) method and the details on the working procedure for prepare nanosized materials were presented along with the comparison to the traditional continuous microwave heating (CMH) method. The nanosized tungsten carbides were synthesized as an example by this novel method. It produced WC with the average particle size of 21.4 nm at the procedure of 15 s-on and 15 s-off for 20 times, however, the particle size increased to 35.7 nm by CMH method for 5 min. The pure WC was obtained by post-treating the sample in NaOH solution, which gave the better performance as support.The nanosized WC was used as support for the Pt nanoparticles (Pt-WC/C(IMH)) for alcohol oxidation and oxygen reduction. It was proved that the Pt-WC/C(IMH) electrocatalysts gave the better performance than that prepared by CMH method (Pt-WC/C(CMH)) or Pt/C electrocatalysts in terms of the activity and CO-tolerance. The intermittent microwave heating method is easier to scale-up for mass production of the nanosized tungsten carbides and other nanosized materials as well. 相似文献
8.
We wish to report a simple and new strategy for the fabrication of gold nanoparticles-conducting polymer film on glassy carbon (GC) and indium tin oxide (ITO) surfaces using 5-amino-2-mercapto-1,3,4-thiadiazole capped gold nanoparticles (AMT-AuNPs) in 0.01 M H2SO4 by electropolymerization. The presence of amine groups on the surface of the AuNPs was responsible for the deposition of the AMT-AuNPs film on the electrode surface. The atomic force microscopy (AFM) studies reveal that the fabricated p-AMT-AuNPs film showed homogeneously distributed AuNPs with a spherical shape of ∼8 nm diameter. The XPS spectrum shows the binding energies at 83.8 and 87.5 eV in the Au 4f region corresponding to 4f7/2 and 4f5/2, respectively. The position and difference between these two peaks (3.7 eV) exactly match the value reported for Au0. The N1s XPS showed three binding energies at 396.7, 399.6 and 403.3 eV, corresponding to the NH, –NH– and –N+H–, respectively, confirming that the electropolymerization proceeded through the oxidation of –NH2 groups present on the periphery of the AMT-AuNPs. The application of the present p-AMT-AuNPs modified electrode was demonstrated by studying the electro reduction of oxygen at pH 7.2. The p-AMT-AuNPs film enhanced the oxygen reduction current more than three times than that of p-AMT film prepared under identical conditions. 相似文献
9.
A novel two-step method was employed to synthesize gold nanoparticles dispersed on boron-doped diamond (BDD) electrode. It consisted of sputter deposition at ambient temperature of maximum 15 equivalent monolayers of gold, followed by a heat treatment in air at 600 °C. Gold nanoparticles with an average diameter between 7 and 30 nm could be prepared by this method on polycrystalline BDD film electrode. The obtained Au/BDD composite electrode appeared stable under conditions of electrochemical characterization performed using ferri-/ferrocyanide and benzoquinone/hydroquinone redox couples in acidic medium. The electrochemical behavior of Au/BDD was compared to that of bulk Au and BDD electrodes. Finally, the Au/BDD composite electrode was regarded as an array of Au microelectrodes dispersed on BDD substrate. 相似文献
10.
E. Laouini M. Hamdani M. I. S. Pereira J. Douch M. H. Mendonça Y. Berghoute R. N. Singh 《Journal of Applied Electrochemistry》2008,38(11):1485-1494
Spinel type Co3O4 thin films, for the oxygen evolution reaction (OER) in 1 M KOH, have been prepared, on stainless steel supports, using the
thermal decomposition method at 400 °C. The electrochemical behaviour of the oxide film/1 M KOH interface was investigated
by cyclic voltammetry and impedance techniques. The impedance measurements were carried out at different positive potentials,
from the open circuit potential to a potential in the OER region and the electrical equivalent circuit, L (R1Q1) (R2Q2) (R3Q3) was used to fit the experimental results. At each potential, a good correlation between experimental and simulated data
is found, thereby validating the proposed equivalent circuit model. The roughness factor value determined in the potential
region where the charge transfer reaction is negligible is similar to that obtained by cyclic voltammetry, with a value of
70 ± 2. 相似文献
11.
An electrochemical method was developed to deposit platinum (Pt) and nickel (Ni) nanoparticles on multi-walled carbon nanotubes (MWCNTs) through a three-step process. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) show the alloy formation for Pt and Ni with a ratio of 1:1. The presence of Pt(0), Ni(0), Ni(OH)2, NiOOH and slight NiO was deduced from XPS data. Electrocatalytic properties of the resulting PtNi/MWCNT electrode for methanol oxidation reaction were investigated. Compared with Pt/MWCNT, an appreciably improved resistance to CO poisoning was observed for the PtNi/MWCNT electrode, which was interpreted by a mechanism based on the bifunctional catalysis. The successful preparation of PtNi/MWCNT nanocomposites opens a new path for an efficient dispersion of the promising electrocatalysts in the direct methanol fuel cells. 相似文献
12.
Pd-Co alloy has been recently proposed as a catalyst for the cathode of direct methanol fuel cells with both excellent oxygen reduction activity and methanol tolerance, hence electrodeposition of this alloy is an attractive approach for synthesizing porous metal electrodes with high methanol tolerance in direct methanol fuel cells. In this study, we electrodeposited two types of Pd-Co films onto Au substrates by applying different current density (−10 or −200 mA cm−2); and then characterized them in terms of morphology, composition, crystal structure, and catalytic activity. Pd-Co deposited at −10 mA cm−2 was smooth and possessed smaller particles (ca. 10 nm), while that at −200 mA cm−2 was dendritic (or rough) and possessed larger particles (ca. 50 nm). Both the Pd-Co alloys were found to be almost the same structure, i.e. a solid solution of ca. Pd7Co3 with Pd-skin, and also confirmed to possess comparable activity in oxygen reduction to Pt (potential difference at 1.0 μA cm−2 was 0.05 V). As for methanol tolerance, cell-voltage was not influenced by addition of 1 mol dm−3 methanol to the oxidant solution. Our approach provides fundamental technique for synthesizing Pd-Co porous metal electrodes by electrodeposition. 相似文献
13.
Sylwia Zoladek Iwona A. Rutkowska Katarzyna Skorupska Barbara Palys Pawel J. Kulesza 《Electrochimica acta》2011,(28):10744
The usefulness of Keggin-type anions (PMo12O403−) as both reducing, capping and activating agents during synthesis of polyoxometallate-modified gold nanoparticles is demonstrated here. Fabrication of gold nanoparticles stabilized with monolayer-type films of inorganic polyoxometallates (e.g. phosphododecamolybdates), Au-PMo12, was achieved by treating an aqueous solution of gold precursor (HAuCl4) with a solution of the partially reduced heteropolyblue molybdate. The choice of temperature strongly affected morphology and size of the resulting Au nanoparticles. The presence of strongly adsorbed molybdate-agents on surfaces of gold nanoparticles was evident from the independent infrared (FTIR by reflectance) and voltammetric experiments. Interfacial polymolybdate anions on Au prevent the particle agglomeration and support formation of the stable colloidal Au-PMo12 solutions. They are colored due to existence of the plasmonic effect. The Au-PMo12 nanoparticles typically had 30–40 nm diameters, and they were used as supports or carriers for dispersed catalytic platinum nanoparticles (of ca. 7–8 nm diameters). Polyoxometallates (PMo12O403−) existing on gold surfaces could also interact with neighboring platinum centers thus acting as “linking” agents facilitating dispersion of Pt nanoparticles. Further, the phosphomolybdate adsorbates (on Au supports) are also likely to activate Pt sites (e.g. by providing reactive hydroxy groups) towards more efficient electrocatalytic oxidation of ethanol both under voltammetric and chronoamperometric conditions. 相似文献
14.
B. El Roustom G. Siné G. Fóti Ch. Comninellis 《Journal of Applied Electrochemistry》2007,37(11):1227-1236
A novel method was developed to synthesize bi-metallic nanoparticles (Au–Pt) on boron-doped diamond (BDD) substrate. This
method consisted of (a) deposition of a small amount of gold (equivalent to a few monolayers) by sputtering on the BDD surface,
(b) heat treatment of the obtained sample at 600 °C in air, resulting in the formation of stable nanoparticles on BDD (Au/BDD
electrode), (c) electrodeposition of Pt on the Au/BDD surface occurring preferentially on the Au nanoparticles, and finally
(d) heat treatment at 400 °C to enhance the interaction between Au and Pt. The ratio between Au and Pt nanoparticles can be
modified by modifying the amount of electrodeposited Pt and was estimated using cyclic voltammetry. These Pt-Au/BDD composite
electrodes were used to study oxygen reduction using both potential sweep (cyclic voltammetry) and hydrodynamic (turbine electrochemical
cell) methods. 相似文献
15.
Ahmad M. Mohammad Mohamed I. Awad Mohamed S. El-Deab Takeyoshi Okajima 《Electrochimica acta》2008,53(13):4351-4358
The electrocatalytic evolution of oxygen gas is investigated at manganese oxide nanorods (nano-MnOx) modified Au, Pt and GC electrodes in a wide range of pH values, ranging from highly acidic to highly basic. Morphological investigation has been carried out by a scanning electron microscopy (SEM), which revealed the deposition of nano-MnOx in a nanorod morphology. A significant enhancement of the electrocatalytic activity of the Au, Pt and GC electrodes towards the oxygen evolution reaction (OER) was observed upon the electrodeposition of nano-MnOx onto the aforementioned electrodes. The effect of the surface coverage of the manganese oxide and the pH of the electrolyte was investigated to seek an optimization. The highest cathodic shift in the onset potential of the OER was obtained in 0.5 M KOH irrespective of the substrate whereas the optimum loading (surface coverage) was about ca. 52%. The origin of the enhancement of the OER is addressed with the assistance of an X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. The preferential electrodeposition of crystallographically oriented nano-MnOx (in the manganite phase, γ-MnOOH) is thought to play the primary role in the observed enhancement. 相似文献
16.
New dynamic aspects of the catalysis of methanol oxidation reaction (MOR) have been studied using quantum mechanical calculations applied to the support-catalyst cluster interactions and surface diffusivity of adsorbed intermediates. For very small catalyst-support clusters, we have found a strong enhancement of the ligand effect for bimetallic catalysts of the type PtnMm attributed to the decreased local density of states near the Fermi level of Pt atoms neighboring the additive metal atom M. This enhancement results in a decreased barrier for surface diffusion of adsorbed COad through the cooperative diffusion mechanism, based on structural relaxation of the catalyst-support cluster, proposed in this work. The strong ligand effect dominates over the Schwoebel potential and trapping well effects, being responsible for accumulation of poisoning intermediates at step sites on the catalyst surface and gradual decrease of catalytic activity with decreasing size of catalyst nanoparticles. The lattice relaxation and strong ligand effects in small catalyst-support clusters lead to lower adsorption energy for COad and thus, to higher reactivity and mobility of reactants and intermediates. The experimental investigations included submonolayer films of bi-functional catalysts (PtRu, PtFe) deposited on novel nanostructured supporting materials, designed with the goal of achieving high variability of their electronic and chemical properties to influence the catalytic activity of sub-monolayer catalyst. The mesoscopic TiO2 supporting film formation was investigated using EQCN, pulse voltammetric and AFM techniques. The conditions for the formation of monodispersed TiO2 nanoparticles with regular nanopores (nanotubes), 20-80 nm in diameter, were described. It follows from EQCN and voltammetric measurements and AFM image analysis that the nanopores are formed by a dissolution-precipitation mechanism. The catalysts, Pt and PtRu, deposited on supporting nanoporous TiO2−x films, were used to study MOR. A lower poisoning effect for cluster PtRu on a TiO2−x support film than that for unsupported PtRu or bare Pt catalysts has been observed. These effects have been attributed to differences in COad binding energy and lowering of activation energy for surface mobility leading to a more facile 2D diffusion of COad from Pt sites to Ru and the supporting TiO2−x. The substrate-catalyst interactions were further investigated using quantum mechanical calculations performed for a model TiO2 nano-ring (representing an orifice of a TiO2−x nanotube studied experimentally) with adlayers of Pt, Ru and Fe catalysts. We have found unusually strong electron delocalization effects for Pt2Fe2 clusters on (TiO2)4 as compared to (TiO2−x)4Pt2Ru2. We have also analyzed various states in surface diffusion of COad on bimetal clusters supported on (TiO2)n and observed considerable dynamic widening of metal-to-metal atom distances induced by CO adsorption (up to 9% for Pt-Pt distance and up to 15% for Fe-Fe distance). We propose that this new dynamic effect leading to cooperative surface diffusion may be further explored in designing novel nanoparticle catalysts. 相似文献
17.
V.S. Dilimon 《Electrochimica acta》2010,55(20):5930-112
The electrochemical reduction of oxygen has been studied on gold, boron-doped diamond (BDD) and glassy carbon (GC) electrodes in a ternary eutectic mixture of acetamide (CH3CONH2), urea (NH2CONH2) and ammonium nitrate (NH4NO3). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry and rotating disk electrode (RDE) voltammetry techniques have been employed to follow oxygen reduction reaction (ORR). The mechanism for the electrochemical reduction of oxygen on polycrystalline gold involves 2-step, 2-electron pathways of O2 to H2O2 and further reduction of H2O2 to H2O. The first 2-electron reduction of O2 to H2O2 passes through superoxide intermediate by 1-electron reduction of oxygen. Kinetic results suggest that the initial 1-electron reduction of oxygen to HO2 is the rate-determining step of ORR on gold surfaces. The chronoamperometric and RDE studies show a potential dependent change in the number of electrons on gold electrode. The oxygen reduction reaction on boron-doped diamond (BDD) seems to proceed via a direct 4-electron process. The reduction of oxygen on the glassy carbon (GC) electrode is a single step, irreversible, diffusion limited 2-electron reduction process to peroxide. 相似文献
18.
Hybrid nanocomposites containing Pt nanoparticles (nano-Pt) and poly(3-methylthiophene) (P3MT) nanorods at glassy carbon surfaces have been successfully prepared by use of an in situ cyclic voltammetry (CV) method. Field emission scanning electron microscope (FE-SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltagrams were used to characterize the properties of these nanocomposites. SEM images showed that nano-Pt were located on the surface of P3MT nanorods and that they formed a three-dimensional (3D) porous nanostructure. EIS and CV results demonstrated that these hybrid nanocomposites had good conductivities, and could accelerate the electron-transfer rates of redox ions. From the results of electrochemical oxidation of methanol and nitrite, we observed that this nanocomposite-modified electrode exhibited excellent electrocatalytic activity, which might be useful in biosensors and/or fuel cells. 相似文献
19.
Esmaeel Darezereshki Mostafa Alizadeh Fereshteh Bakhtiari Mahin Schaffie Mohammad Ranjbar 《Applied Clay Science》2011,54(1):107-111
In this research work, ZnO nanoparticles were prepared by direct thermal decomposition method with Zn4(SO4)(OH)6·0.5 H2O as a precursor. The precursor was calcinated in air for 1 h at 825 °C. Samples were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), infrared spectrum (IR), and scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD, EDS, and IR results indicated that the ZnO nanoparticles were pure. The average crystallite and particle size of the ZnO nanoparticles were estimated to be 87 nm and 92 nm by XRD and TEM, respectively. The SEM and TEM images showed that the ZnO nanoparticles were of spherical shape. The simplicity of the present method suggests its potential application at industrial scale as a cheap and convenient way to produce pure ZnO nanoparticles from low concentration ZnSO4 solutions. 相似文献