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1.
Mass transfer measurements were carried out to test a disk-shaped parallel-plate electrochemical cell, based on a new design.
The impinging-jet-cell concept, confined between parallel plates, was adapted to a configuration with one central inlet and
several peripheral exit sections, leading to more effective hydrodynamics within the cell. Measurements of mass transfer coefficient
were performed using the limiting diffusion current technique based on ferro-cyanide ion oxidation, and overall mass transfer
coefficients were correlated to Reynolds numbers ranging from 30 to 200.
A comparison with literature on similar devices showed higher mass transfer coefficients can be obtained in the cell described
in the present work. From the mass transfer standpoint, this type of cell could be a valuable tool in electrochemical wastewater
treatment applications.
The electrochemical oxidation of oxalic acid was tested at different anode materials (Pb/PbO2, boron-doped diamond, Ti/Pt and Ti/IrO2–Ta2O5), showing that the new cell design enables limitations usually encountered with conventional batch cells to be overcome.
However, the nature of the anode material remains an important parameter for the elimination of organic substrates. 相似文献
2.
Kinetic modelling of the electrochemical mineralization of organic pollutants for wastewater treatment 总被引:1,自引:0,他引:1
Agnieszka Kapałka György Fóti Christos Comninellis 《Journal of Applied Electrochemistry》2008,38(1):7-16
The electrochemical mineralization of organic pollutants is a new technology for treatment of dilute wastewater (COD < 5 g L−1). In this method, use of the electrical energy can produce complete oxidation of pollutants on high oxidation power anodes.
An ideal anode for this type of treatment is a boron-doped diamond electrode (BDD) characterized by a high reactivity towards
oxidation of organics. In the present work kinetic aspects of organic mineralization is discussed. The proposed theoretical
kinetic model on boron-doped diamond anodes is in excellent agreement with experimental results. In addition economic aspects
of electrochemical organic mineralization are reported. 相似文献
3.
M. D. Krotova Yu. V. Pleskov V. P. Varnin I. G. Teremetskaya 《Journal of Applied Electrochemistry》2010,40(10):1839-1844
The electrochemical behavior of polycrystalline diamond films of different thickness (0.5–7 μm), grown by hot-filament CVD
method, was studied by electrochemical impedance spectroscopy and cyclic voltammetry. The differential capacitance, background
current, and potential window were measured in supporting electrolyte solution; the electrochemical kinetics, in [Fe(CN)6]3−/4− model redox system. With the increasing of the films thickness, the crystallite size increased; both the differential capacitance
and background current in the indifferent electrolyte, as well as the transfer coefficients in the redox system, decreased;
thus, the diamond electrode becomes as if less reversible. The effect of the films’ thickness is reduced to that of nondiamond
(amorphous) carbon contribution from intercrystalline boundaries on the electrochemical behavior of the polycrystalline diamond
electrodes. 相似文献
4.
K. Subramanian K. Asokan D. Jeevarathinam M. Chandrasekaran 《Journal of Applied Electrochemistry》2007,37(2):255-260
An electrochemical reactor with anode and cathode chambers separated by a composite perfluoro polymer cation exchange membrane
was designed, fabricated and used for the reduction of dissolved carbon dioxide under ambient conditions to formate. The flow
reactor enhanced the mass transfer of carbon dioxide compared to the batch reactor and maximum current efficiency of 93% for
formate formation was obtained. A formate concentration of 1.5 × 10−2 mol dm−3 was obtained. Experiments were conducted using two different perfluoro polymer membranes – Nafion 961 and Nafion 430. Optimum
values of flow rate and current density were evaluated for the energy efficient formation of formate in aqueous phosphate
buffer solutions. 相似文献
5.
Characterization of the performance and failure mechanisms of boron-doped ultrananocrystalline diamond electrodes 总被引:1,自引:1,他引:0
This research investigated the anodic stability of boron-doped ultrananocrystalline diamond (BD-UNCD) film electrodes on a
variety of substrates (Si, Ta, Nb, W, and Ti) at a current density of 1 A cm−2. At an applied charge of 100 A h cm−2, measurable BD-UNCD film wear was not observed using SEM cross-sectional measurements. However, anodic treatment of the electrodes
resulted in surface oxidation and film delamination, which caused substantial changes to the electrochemical properties of
the electrodes. The substrate roughness, substrate electroactivity, and compactness of the substrate oxide were key parameters
that affected film adhesion, and the primary mechanism of electrode failure was delamination of the BD-UNCD film. Substrate
materials whose oxides had a larger coefficient of thermal expansion relative to the reduced metal substrates resulted in
film delamination. The approximate substrate stability followed the order of: Ta > Si > Nb > W ≫ Ti. 相似文献
6.
Giancarlo R. Salazar-Banda Adriana E. de Carvalho Leonardo S. Andrade Romeu C. Rocha-Filho Luis A. Avaca 《Journal of Applied Electrochemistry》2010,40(10):1817-1827
The electrochemical activation and physical degradation of boron-doped diamond (BDD) electrodes with different boron doping
levels after repeated cathodic pretreatments are reported. Galvanostatic cathodic pretreatment passing up to −14000 C cm−2 in steps of −600 C cm−2 using −1 A cm−2 caused significant physical degradation of the BDD surface, with film detachment in some areas. Because of this degradation,
a great increase in the electrochemically active area was observed in Tafel plots for the hydrogen evolution reaction (HER)
in acid media. The minimum cathodic pretreatment needed for the electrochemical activation of the BDD electrodes without producing
any observable physical degradation on the BDD surfaces was determined using electrochemical impedance spectroscopy (EIS)
measurements and cyclic voltammetry: −9 C cm−2, passed at −1 A cm−2. This optimized cathodic pretreatment can be safely used when electrochemical experiments are carried out on BDD electrodes
with doping levels in the range between 800 and 8000 ppm. 相似文献
7.
A Ti/SnO2–Sb2O4 electrode was prepared by alternate Sn and Sb electrodepositions using the thermo-electrochemical method. The chemical, electrochemical,
and structural characterization of the electrode was performed and it was tested in the anodic oxidation of several pollutants,
phenol, ibuprofen, acid orange 7 (AO7), and diclofenac, all in aqueous 0.035 M Na2SO4 solutions at current densities of 10 and 20 mA cm−2. After the 24 h assay, removal of chemical oxygen demand, total organic carbon (TOC) and absorbance were very high, especially
at the higher current density. TOC removals presented the lowest value. However, after 24 h at 20 mA cm−2, TOC removals were: phenol—94%; ibuprofen—83%; AO7—88%; and diclofenac—73%. Combustion efficiency and instantaneous and mineralization
current efficiencies were also determined. 相似文献
8.
Cathodic reaction kinetics and its implication on flow-assisted corrosion of aluminum alloy in aqueous ethylene glycol solution 总被引:1,自引:0,他引:1
The cathodic reaction kinetics and anodic behavior of Al alloy 3003 in aerated ethylene glycol–water solution, under well-controlled
hydrodynamic conditions, were investigated by various measurements using a rotating disk electrode (RDE). The transport and
electrochemical parameters for cathodic oxygen reduction were fitted and determined. The results demonstrate that the cathodic
reaction is a purely diffusion-controlled process within a certain potential region. The experimentally fitted value of diffusion
coefficient of oxygen is 3.0 × 10−8 cm2 s−1. The dependence of cathodic current on rotation speed was in quantitative agreement with Levich equation. At potentials more
positive than the diffusion controlled region, the cathodic process was controlled by both diffusion and electrochemical kinetics.
The electrochemical reaction rate constant, k
0, was determined to be 1.1 × 10−9 cm s−1. There is little effect of electrode rotation on anodic behavior of Al alloy during stable pitting. However, fluid hydrodynamics
play a significant role in formation of the oxide film and the Al alloy passivity. An enhanced electrode rotation would increase
the mass-transfer rate of solution, and thus the oxygen diffusion towards the electrode surface for reduction reaction. The
generated hydroxide ions are favorable to the formation of Al oxide film on electrode surface. 相似文献
9.
Elsa Weiss Karine Groenen-Serrano André Savall 《Journal of Applied Electrochemistry》2007,37(11):1337-1344
Results are reported of the electrochemical oxidation of sodium dodecylbenzenesulfonate (SDBS), a common surfactant, at boron-doped
diamond anodes. The measured critical micelle concentration (CMC) for SDBS in water at 24 °C was almost 150 mg dm−3, but this decreased to almost 30 mg dm−3 in 0.1 M sodium sulfate. Cyclic voltammetry of a boron doped diamond (BDD) electrode in aqueous SDBS solutions exhibited
oxidation current densities at very positive potentials; however, solutions of monomers at concentrations <CMC gave rise to
higher current densities than in higher concentration solutions that formed micelles. Galvanostatic electrolyses, with samples
analyzed for Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD), were performed in an electrolytic flow cell without
separator, operating in batch recycle mode, using solutions containing SDBS at initial concentrations of 25 and 250 ppm. SDBS
in basic media (pH = 12) exhibited lower TOC removal rates than in acidic or neutral solutions, due to concurrent oxidation
of dissolved carbonates at potentials less positive than required for water oxidation, as evident in cyclic voltammograms.
Decreasing the [electrolyte]/[surfactant] ratio from 200 to 10 increased TOC removal rates. For solutions containing monomers,
TOC removal rates also increased with flow rate in the second part of the electrolysis, corresponding to reaction of smaller,
fragmented organic compounds. When COD removal from a solution containing SDBS micelles was mass transport controlled, current
efficiencies were constant at ca. 50%, due to dimerisation of hydroxyl radical to H2O2 and its oxidation to dioxygen. 相似文献
10.
In order to develop the new anode materials for Al/air batteries, electrochemical properties of pure aluminium (99.999 %),
technical grade aluminium (99.8 %) and the alloys with indium and tin, i.e. Al—0.1 % In, Al—0.2 % Sn and Al—0.1 % In—0.2 %
Sn have been investigated in 2 mol dm−3 NaCl solution. The aluminium materials were polarized anodically in the range 20–100 mA cm−2 for a 30 min period. During the anodic polarization variation in potential was recorded as a function of time and the simultaneous
hydrogen evolution was measured. The rate of hydrogen evolution reaction was found to increase with increasing anodic polarization
which is characteristic of the negative difference effect. The additional information concerning the corrosion behaviour of
the tested materials was provided by light microscope imaging. The results show that the examined technical grade aluminium
alloys could serve as suitable anodes for Al/air batteries containing sodium chloride electrolyte; with Al–In exhibiting the
most remarkable characteristics. The addition of In as alloying component to aluminium reduces electrode polarization, decreases
hydrogen evolution rate and increases the anode efficiency. 相似文献
11.
Jubing Zhang Zhaoping Zhong Jianmin Xiao Zongming Fu Jinxiao Zhao Weiling Li Min Yang 《Korean Journal of Chemical Engineering》2011,28(8):1773-1778
A fluidized bed electrode could lower concentration polarization and activation polarization because of its high mass and
heat transfer coefficient. The polarization characteristics of the fluidized bed electrode are systematically investigated
in a molten carbonate fuel cell anode with an O2/CO2/gold reference electrode. The results show that polarization performance of the anode is improved by selecting proper flow
rates of H2, O2 and CO2, choosing suitable nickel particle content together with appropriate O2/CO2 ratio, and increasing reaction temperature as well as the area of the current collector. Limiting current density of 115.56
mA·cm−2 is achieved under optimum performance as follows: a cylindrically curved nickel plate current collector, nickel particle
content of 7.89%, the reaction temperature of 923 K, H2 flow rate of 275 mL·min−1, O2/CO2 flow rate of 10/20 mL·min−1 and O2/CO2 ratio of 1 : 2. 相似文献
12.
Mathieu Boillot Caroline Bonnet Sophie Didierjean François Lapicque 《Journal of Applied Electrochemistry》2007,37(1):103-110
The paper presents electrochemical measurements carried out in a PEMFC with a view to determining the separate kinetics of
the electrode reactions. For this purpose, the separate response of one electrode (anode or cathode) was magnified by dilution
of the reacting gas, respectively hydrogen and oxygen, and comparison of the experimental data in the form of steady voltage-current
variations and impedance spectra. Experiments were carried out at 60 °C and ambient pressure. Water management was thoroughly
controlled so that the gases leaving the cell had the same relative humidity in all experiments of one series. Hydrogen oxidation,
although rapid, corresponds to overpotentials up to 50 mV at high dilution rates and current densities. Assuming a Tafel–Volmer
mechanism, the exchange current density of the anode reaction at the Pt surface is of the order of 1 mA cm−2. The two techniques employed led to Tafel slopes of oxygen reduction ranging from 120 to 150 mV/decade, with an exchange
current density near 1 μA cm−2, in good agreement with published data. 相似文献
13.
A Si thin film of thickness 275 nm was deposited on rough Cu foil by magnetron sputtering for use as lithium ion battery anode
material. X-ray diffraction (XRD) and TEM analysis revealed that the Si thin film was completely of amorphous structure. The
electrochemical performance of the Si thin film was investigated by cyclic voltammetry and constant current charge/discharge
test. The film exhibited a high capacity of 3,134 mAh g−1 at 0.025 C rate. The capacity retention was 61.3% at 0.5 C rate for 500 cycles. An island structure formed on the Cu foil
substrate after cycling adhered to the substrate firmly and provided electrical connection. This is the possible reason for
the long cycling life of Si thin film anode. Moreover, the cycling performance was further improved by annealing at 300 °C.
The Li+ diffusion coefficients (D
0) of Si thin film, measured by cyclic voltammetry, are 1.47 × 10−9 cm2 s−1 and 2.16 × 10−9 cm2 s−1 for different reduced peaks. 相似文献
14.
Reda Karoum Antonio de Lucas-Consuegra Fernando Dorado Jose Luis Valverde Alain Billard Philippe Vernoux 《Journal of Applied Electrochemistry》2008,38(8):1083-1088
The electrochemical promotion of catalysis (EPOC) of propene combustion was investigated using Pt sputtered thin film on an
O2− conductor, 8 mol% Y2O3-stabilized-ZrO2 (YSZ). In order to separate the influence of the thermal migration of the O2− oxide ions from the electrolyte to the catalyst surface and the impact of an electrical polarization on the catalytic activity,
several light-off experiments (cool down and heat up procedures) were successively performed under different polarizations,
i.e. OCV, +2 and −2 V. These experiments have clearly shown that the presence of O2− (thermally or electrochemically induced) inhibits the catalytic activity of the platinum for the propene deep oxidation.
These results demonstrate the importance to define a normalized rate enhancement ratio, ρ
n
, from a reference value of the catalytic rate corresponding to a Pt surface state free of O2− ions. 相似文献
15.
16.
In this work a undivided parallel plate cell equipped with boron doped diamond (BDD) anode was tested as electrochemical reactor
for disinfection of water. Two configurations were adopted: a single pass configuration (SPC) and a recirculated configuration
(RC) in which also a reservoir was inserted in the hydraulic circuit. In both the experimental configurations the system worked
in continuous mode with a flow rate ranging from 0.05 to 0.42 dm3 min−1; in the RC the recirculating flow rate ranged from 0.45 to 6 dm3 min−1. Thermostated (25 °C) galvanostatic electrolyses were carried out with aqueous solutions containing 100 mg dm−3 of chloride ions: values of current density from 2.5 to 5.0 mA cm−2 were used. Steady state data revealed that active chlorine and chlorate ions were the main oxidation products. Particular
attention was paid to the hydrodynamics both for SPC and RC: pulse-response curves were experimentally obtained with an inert
tracer, and the behaviour of the system was interpreted by models based on a combination of ideal flow reactors, bypass flow
elements, and dead zones. The hydrodynamic models were utilized to predict the outlet concentration of the electrolysis products.
A good agreement between model predicted and experimental data was obtained for a wide range of experimental conditions. Preliminary
disinfection tests were then performed using Escherichia coli as model microorganism. Results were discussed in terms of both disinfection efficiency and by-products formation. 相似文献
17.
Leonardo M. Da Silva Débora V. Franco Lindomar G. Sousa Ismael C. Gonçalves 《Journal of Applied Electrochemistry》2010,40(4):855-864
The filter-press electrochemical ozonizer is characterized as a function of the applied electric current, temperature, and
linear velocity of the electrolyte-free water. Lead dioxide electroformed on surface of a non-platinized fine mesh stainless
steel support was used as anode. Electrolysis of the electrolyte-free water was carried out using the membrane electrode assembly
(MEA) adequately compressed by means of a specially designed clamping system. Electrochemical characterization studies were
carried out galvanostatically as a function of temperature and linear velocity of the circulating water. It was verified that
the electrochemical ozone production (EOP) taking place at the reacting zones formed at the solid polymer electrolyte (SPE)/mesh
electrode interface is not considerably affected by circulating water when the linear velocity inside the distribution channels
is higher than 1.20 cm s−1. A current efficiency for the EOP of 13% and a specific electric energy consumption of 70 Wh g−1 were obtained when an electric current of 130 A was applied at 30 °C. The reactor service life test revealed that the MEA
using the lead dioxide fine mesh electrode as anode and a fine mesh stainless steel electrode as cathode, pressed against
the SPE, is stable for the ozone production. 相似文献
18.
Pseudo two-dimensional finite element models were developed to predict the hypochlorite (chloric(I)) (HOCl + OCl−) production by electrolysis of near-neutral aqueous sodium chloride solution, in reactors with (a) an anode and cathode in
the form of plates, and (b) a lead dioxide-coated graphite felt anode and titanium plate cathode. The model was used to investigate
the feasibility of using a porous anode to achieve high single pass conversions in oxidising chloride ions. For the model
reactor with planar anode, the effects of diffusion, migration and convection on the mass transport of the reacting species
were considered, whereas with the porous anode, a supporting electrolyte (Na2SO4) was notionally present to eliminate the migrational contribution to reactant transport. For an electrolyte flow rate of
10−6 m3 s−1 (Re = 10 for plate electrodes, Re
porous = 0.76 for porous anode), a cell voltage of 3.0 V and an inlet NaCl of 100 mol m−3, the single-pass conversion of Cl− was predicted to increase from 0.45 for the reactor with a planar anode to 0.81 for the reactor with a porous anode. For
the same operating conditions, the overall current efficiency was also predicted to increase from 0.71 to 0.77 by replacing
the plate with the porous anode. 相似文献
19.
Noureddine Belhadj Tahar Ridha Abdelhédi André Savall 《Journal of Applied Electrochemistry》2009,39(5):663-669
This paper deals with the treatment of aqueous phenol solutions using an electrochemical technique. Phenol can be partly eliminated
from aqueous solution by electrochemically initiated polymerisation. Galvanostatic electrolyses of phenol solutions at concentration
up to 0.1 mol dm−3 were carried out on a Ta/PbO2 anode. The polymers formed are insoluble in acidic medium but soluble in alkaline. These polymers were filtered and then
dissolved in aqueous solution of sodium hydroxide (1 mol dm−3). The polymers formed were quantified by total organic carbon (TOC) measurement. It was found that the conversion of phenol
into polymers increases as a function of initial concentration, anodic current density, temperature, and solution pH. The
percentage of phenol polymerised can reach 15%. 相似文献
20.
The bulk B-doped polycrystalline diamond (PCD) electrode in this study was prepared by high-pressure, high-temperature (HPHT)
technology. The PCD was sintered under HPHT conditions, using B-doped diamond powders and a metal catalyst as raw materials,
then the metal solvent phase was dissolved by aqua regia. The morphology and composition of the PCD were investigated with
a scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersion spectrum (EDS). The results show that
the sintered body possesses a polycrystalline structure with direct diamond–diamond bond and irregularly shaped pores of 1–10 μm
distributed on the grain boundaries after the metal solvent phase was removed. The cyclic voltammogram and electrochemical
impedance spectroscopy of this B-doped electrode have been investigated. The B-doped PCD electrode exhibits stable electrochemistry
in a KCl support solution over a wide potential range. The quasi-reversible reaction occurs on the electrode for the [Fe(CN)6]3−/4− couples. The electrode process combines the diffusion-controlled mass transport plus the kinetic process. The electrochemical
impedance spectroscopy (EIS) analysis shows the porous structure characteristic of the PCD electrode. 相似文献