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1.
The impedance of the anodically formed hydrous Ru oxide in the system Ru|oxide film|1 M HClO 4 solution has been studied in the range of potentials where the electrode process occurs by a double electron and proton exchange between the oxide film and the solution. The results allowed us to clearly distinguish between the surface process at higher frequency and the bulk process at lower frequency. The high-frequency charging is found to be coupled to Faradaic charging at the film/solution interface. Evaluation of the impedance data at lower frequency, using diffusion equations for the finite boundary conditions, yields an effective proton diffusion coefficient to be 10 −10 to 10 −11 cm 2 s −1.Oxygen reduction on the spontaneously oxidized ruthenium electrode was discussed on the basis of a rotating ring-disk voltammetry. 相似文献
2.
Effects of the sodium acetate (NaCH 3COO, denoted as NaAcO) concentration, plating temperature, and oxide loading on the pseudocapacitive characteristics of hydrous ruthenium oxide (denoted as RuO 2· xH 2O) films anodically plated from aqueous RuCl 3· xH 2O media were systematically investigated in this work. The electrochemical behavior of RuO 2· xH 2O with annealing in air at 200 °C for 2 h is approximately independent of the NaAcO concentration and plating temperature although a negative shift in the onset and peak potentials of deposition with rising the plating temperature is found. The morphologies and adhesion of RuO 2· xH 2O deposits strongly depend on the deposition rate which is obviously influenced by varying the above two deposition variables. The specific capacitance of RuO 2· xH 2O is monotonously decreased from 760 to 505 F g −1 when the oxide loading is gradually increased from 0.34 to 1.0 mg cm −2, due to the longer pathways of both electrons and protons during the redox transitions. The XRD and Raman spectroscopic analyses reveal the extremely localized crystalline nature of as-deposited RuO 2· xH 2O. All RuO 2· xH 2O deposits show the ideal pseudocapacitive characteristics, definitely illustrating the merits of RuO 2· xH 2O prepared by anodic deposition without considering the advantages of its simplicity, one-step, reliability, low cost, and versatility for electrode preparation. 相似文献
3.
Hydrothermal treatment (HTT) of RuO 2-Ta 2O 5/Ti electrode, as a method for improving their performance, for use in supercapacitors was investigated.The results show that HTT significantly enhances the stability of the electrodes. The specific capacitance of electrodes, subject to HTT in the temperature range 180-250 °C remains unchanged after 1000 CV cycles between −0.2 and 1.1 V vs. SCE; without HTT a decay to 97% of the initial is observed. The results also show that HTT decreases the activity of the electrodes for O 2 and H 2 evolution and increases the voltage window by 56-135 mV for supercapacitors, but with a specific capacitance decrease of 7-27%. XPS analyses show the existence of more hydroxides after the HTT, which leads to a little increase in the interplanar distance as indicated in the XDR results. Contact angle measurements show the presence of a more hydrophilic surface after HTT. 相似文献
4.
In this work, degradation of C.I. Acid Red 33 (AR33) in aqueous solutions was investigated. The combined electrolysis–ozone (ECO) process optimized based on SnO 2 nanoparticles electrode (nano-SnO 2/Ti) as anode using response surface methodology (RSM) involving a five-level central composite design (CCD). The nano-SnO 2/Ti electrode was prepared using electrophoretic deposition (EPD) method. The electrode was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). The initial pH, current density, reaction time and electrolyte concentration were selected as independent variables in central composite design while color removal efficiency was considered as the response function. Based on analysis of variance (ANOVA), the coefficient of determination value ( R2 = 0.981) was high. In optimum conditions, maximum color removal efficiency (93.2%) was obtained after 16 min; and the removal of chemical oxygen demand (COD) was reduced to 57.1% after 60 min. 相似文献
5.
The effect of PTFE addition was investigated for the electrophoretic deposition (EPD) of hydrous ruthenium oxide electrodes. Mechanical stability of electrode layers, together with deposition yield, was enhanced by using hydrous ruthenium oxide/PTFE dispersions. High supercapacitor performance was obtained for the electrodes prepared with 2% PTFE and 10% water. When PTFE content was higher, the rate capability became poor with low electronic conductivity; higher water content than 10% resulted in non-uniform depositions with poor cycleability and power capability. When electrodes were heat treated at 200 °C for 10 h, the specific energy was as high as 17.6 Wh/kg based on single electrode (at 200 W/kg); while utilizable energy was lower with heat treatment time of 1 and 50 h, due to the high resistance and gradual crystallization, respectively. With PTFE addition and heat treatment at 200 °C for 10 h, the specific capacitance was increased by 31% (460 → 599 F/g at ca. 0.6 mg/cm 2) at 10 mV/s, and the deposition weight was increased up to 1.7 mg/cm 2 with initial capacitance of 350 F/g. 相似文献
6.
PbO 2 electrodes doped with rare earth oxides (Re-PbO 2), including Er 2O 3, Gd 2O 3, La 2O 3 and CeO 2, were prepared by anodic codeposition in order to investigate the effect of rare earth oxide dopants on the properties of PbO 2 electrodes. The physicochemical properties of the Re-PbO 2 electrodes were analyzed by spectral methods and electrochemical measurements. The surface morphology of the Re-PbO 2 electrodes held the characteristics of the dopants and the crystal grain of PbO 2. The crystal structure of the PbO 2 electrodes was also influenced by doping with different rare earth oxides. The presence of Er 2O 3 and La 2O 3 in the PbO 2 films could enhance the direct anodic oxidation, which was helpful to mineralize 4-chlorophenol. The 4-chlorophenol decay on the Re-PbO 2 electrodes was analyzed and good fitting was found using the relation for the pseudo-first order reaction. Of the electrodes examined, the Er-PbO 2 electrode exhibited the best performance for the degradation of 4-chlorophenol. The removal rates of COD and 4-chlorophenol during the 9 h electrolysis at a current density of 20 mA cm −2 were 80.7 and 100%, respectively, with the current efficiency being 16.0-10.1%. 相似文献
7.
Pitting corrosion of Pb in Na 2CO 3 solutions (pH=10.8) containing NaNO 3 as a pitting corrosion agent has been studied using potentiodynamic anodic polarization, cyclic voltammetry and chronoamperometry techniques, complemented with scanning electron microscopy (SEM) examinations of the electrode surface. In the absence of NO 3−, the anodic voltammetric response exhibits three anodic peaks prior to oxygen evolution. The first anodic peak A 1 corresponds to the formation of PbCO 3 layer and soluble Pb 2+ species in solution. The second anodic peak A 2 is due to the formation of PbO beneath the carbonate layer. Peak A 2 is followed by a wide passive region which extends up to the appearance of the third anodic peak A 3. The later is related to the formation of PbO 2. Addition of NO 3− to the carbonate solution stimulates the anodic dissolution through peaks A 1 and A 2 and breaks down the dual passive layer prior to peak A 3. The breakdown potential decreases with an increase in nitrate concentration, temperature and electrode rotation rate, but increases with an increase in carbonate concentration and potential scan rate. Successive cycling leads to a progressive increase in breakdown potential. The current/time transients show that the incubation time for passivity breakdown decreases with increasing the applied anodic potential, nitrate concentration and temperature. 相似文献
8.
From aqueous solutions, gold was deposited on freshly polished titanium surface either by displacement reaction or by potentiodynamic polarization. Both of these procedures resulted in the formation of Au/TiO 2 composite layer over the titanium surface, although with quite different Au content. The electrochemical behaviour of these composite layers was examined in 0.1 M NaOH solution, both oxygen free and oxygen saturated, using rotating disc technique. In the potential region of oxygen reduction reaction, the Au/TiO 2 layer obtained by potentiodynamic polarization, displayed the voltammetric curve similar to that observed on (1 0 0) plane of Au monocrystal. The Koutecky-Levich analysis evidenced that 4e − route of oxygen reduction dominates on both type of composite layers. 相似文献
9.
A [Ru(bpy) 3] 2+ (bpy = 2,2′-bipyridine)/WO 3 hybrid (denoted as Ru-WO 3) film was prepared as a base layer on an indium tin oxide electrode by electrodeposition from a colloidal solution containing peroxotungstic acid, [Ru(bpy) 3] 2+ and poly(sodium 4-styrenesulfonate). A ruthenium purple (RP, Fe III4[Ru II(CN) 6] 3, denoted as Fe III-Ru II) layer was electrodeposited on a neat WO 3 film or a Ru-WO 3 film from an aqueous RP colloid solution to yield a WO 3/RP bilayer film or a Ru-WO 3/RP bilayer film, respectively. The spectrocyclic voltammetry measurement reveals that Fe II-Ru II is oxidized to Fe III-Ru II by a geared reaction of [Ru(bpy) 3] 2+/3+ and Fe III-Ru II is reduced by a geared reaction of H xWO 3/WO 3 in the Ru-WO 3/RP film. These geared reactions produced electrochromic hysteresis of the RP layer. However, the absorbance change in the hysteresis was smaller than that for the Ru-WO 3/Prussian blue bilayer film reported previously, resulting from the lower electroactivities of any redox component for the Ru-WO 3/RP film. The lower electroactivities could be explained by the specific interface between the Ru-WO 3 and RP layers. It might contribute to either an increase of the interfacial resistance between the Ru-WO 3 and RP layers, or formation of the physically precise interface between the layers to make it difficult for counter ions to be transported in the interfacial liquid phase involved in the redox reactions in the film. The specific interface at the Ru-WO 3 and RP layers could be formed possibly by the electrostatic interaction between [Ru(bpy) 3] 2+ and terminal [Ru(CN) 6] 4− moieties of RP. It could be suggested by the decreased redox potential of [Ru(bpy) 3] 2+ in the Ru-WO 3 layer from 1.03 to 0.61 V by formation of the RP layer. 相似文献
10.
The conversion of fuel-nitrogen to HCN and NH 3 and to nitrogen oxides was studied with nitrogen-containing model compounds, chosen to represent the main nitrogen and oxygen functionalities in fossil fuels. Two kinds of experiments were performed in an entrained-flow reactor at 800 °C. The conversion of model-compound-N to HCN and NH 3 was determined under inert conditions, and the formation of NO, N 2O and NO 2 was determined under oxidizing conditions. In inert atmosphere, oxygen-containing functional groups had an important effect on the ratio of HCN to NH 3. In particular, OH groups bound directly in the ring structure increased the conversion of nitrogen to NH 3. In oxidizing atmosphere, the conversions of model-compound-N to N 2O were high, but the substituent groups had no well-defined effect on the ratio of N 2O to NO. The formation of NO 2 was insignificant. 相似文献
11.
Tantalum(V) and niobium(V) oxide films, which are typically difficult to prepare by electrochemical methods using aqueous solutions, are easily fabricated in an acetone bath using Ta and Nb anodes as the metal sources and a metal-free solvent containing halide ions as the supporting electrolyte. At the initial stage of electrolysis, anodic oxidation of the metal anode proceeds in the presence of water as an impurity in the acetone solvent. Subsequently, pitting corrosion of the oxide film on the metal anode occurs as a result of the action of halide ions. In this stage, anodic corrosion proceeds only in the presence of Br 2, and not in acetone containing I 2. Finally, Ta or Nb species are deposited directly on the cathode surface via the reactions with cathodically generated hydroxide ions, and the films need to be annealed at high temperature to effect crystallization. In these processes, the metal plate acts as a soluble anode with respect to Br − and as a metal source for electrodeposition. The coating on a stainless steel substrate prepared by the present technique acts as an effective barrier against electrolytic corrosion. 相似文献
12.
The modification of a gold electrode surface by electropolymerization of trans-[Ru(NH 3) 4(Ist)SO 4] + to produce an electrochemical sensor for nitric oxide was investigated. The influence of dopamine, serotonin and nitrite as interferents for NO detection was also examined using square-wave voltammetry (SWV). The characterization of the modified electrode was carried out by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and SERS techniques. The gold electrode was successfully modified by the trans-[Ru(NH 3) 4(Ist)SO 4] + complex ion using cyclic voltammetry. The experiments show that a monolayer of the film is achieved after ten voltammetric cycles, that NO in solution can coordinate to the metal present in the layer, that dopamine, serotonin and nitrite are interferents for the detection of NO, and that the response for the nitrite is much less significant than the responses for dopamine and serotonin. The proposed modified electrode has the potential to be applied as a sensor for NO. 相似文献
13.
Polycrystalline BaTiO 3 (BTO) thin films were electrodeposited on titanium foils from colloidal aqueous solutions of BTO nanoparticles which were synthesized by a hydrothermal process, under autogenous conditions. Two kinds of reactants have been studied: one involves an aqueous solution of titanium tetrachloride and barium hydroxide octahydrate without any added solvent, whereas the second was obtained by dispersing amorphous titanium oxide in different volumes of barium hydroxide aqueous solutions. The nanoparticles were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The particle size distribution (PSD) and the zeta potential measurements indicate that the colloids in the solution are polydisperse when using the first synthesis method, and they tend to be quasi monodisperse in the case of the second synthesis route. A porous microstructure of the electrodeposited films was detected by SEM. Finally, the dielectric properties of the BTO thin films were investigated. 相似文献
14.
A series of perovskite catalysts was investigated for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte and at room temperature, supplied by oxygen or air. A meniscus cell was used to screen-test candidate catalysts for their bifunctionality and assess their activity for ORR at 3 mm depth of immersion (DOI) in the electrolyte. Based on the meniscus data LaNiO 3, La 0.1Ca 0.9MnO 3 and La 0.6Ca 0.4CoO 3 were selected for further assessment in microelectrode and half-cell studies. Activity tests for the ORR and OER, Tafel slopes at high current densities and apparent activation energies for the ORR were determined using a microelectrode technique on samples of the selected perovskites, La 0.1Ca 0.9MnO 3, La 0.6Ca 0.4CoO 3 and LaNiO 3 with and without graphite support. Tafel slopes of ca. 120 mV per decade and apparent activation energies of approximately 18 kcal mol −1 were measured at high cathodic current densities. Cycle-life and performance of La 0.1Ca 0.9MnO 3, La 0.6Ca 0.4CoO 3 and LaNiO 3-based gas-diffusion electrodes in half-cell configurations were tested at a constant current density of 25 mA cm −2 with subsequent and intermittent polarizations. Similar activities resulted in the ORR, while increased numbers of cycles were observed for the La 0.1Ca 0.9MnO 3-based electrode. Furthermore, electrode material compositions, especially PTFE contents were optimized to conform to the establishment of the three phase interactions of the electrode structure. Transmission Electron microscopy (TEM) and BET-surface area analyses were carried out in order to find out the morphological and surface properties of the perovskite materials. 相似文献
15.
In general, the strain effect and the electrostatic effect are important factors influencing the electrical properties of ferroelectric superlattices. However, the interfacial diffusion may also greatly influence the electrical properties of ferroelectric superlattices. Here, we deposited PbTiO 3/PbZrO 3 (PTO/PZO) superlattices on Nb-doped SrTiO 3 (NSTO) single-crystal substrates by pulse laser deposition with the same deposition processes but different cooling processes to explore the effects of interface diffusion on the structural and electrical properties of the superlattices. The experimental results showed that with increasing the holding time in the cooling process after deposition, the ferroelectric and dielectric properties were enhanced, meanwhile, the leakage current density was reduced. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) results showed that the PTO/PZO interfaces became blurred with increasing cooling time. Therefore, the increase in ferroelectric and dielectric properties and the decrease in leakage current density may be due to the interdiffusion of Ti and Zr ions at the PTO/PZO interfaces resulting in the formation of Pb(Zr xTi 1-x)O 3 (PZT) and the decrease of interface defects at the PTO/PZO interfaces. Our results demonstrate that besides the strain and electrostatic effects, the interdiffusion of the elements at the interfaces is also an important factor that influences the electrical properties of ferroelectric superlattices. 相似文献
16.
Stable suspensions based on methylethylketone (MEK), n-butylamine and nitrocellulose were developed for the electrophoretic deposition (EPD) of Al 2O 3 and ZrO 2 powder. Deposits with a high green density, smooth surface and high deposition yield were obtained upon adding 10–15 vol.% n-butylamine in combination with 1 wt.% nitrocellulose. The influence of the reaction between MEK and n-butylamine, forming water and imines, on the electrophoretic deposition behaviour was investigated. Experimental results revealed that the zeta potential is not a straightforward indication of the stability of these suspensions, since the maximum absolute zeta potential did not correspond with a maximum suspension stability, due to the additional electrosteric stabilisation of the adsorbed charged nitrocellulose. 相似文献
17.
It is shown that introduction of additives of rare-earth element oxides (La 2O 3, CeO 2) enables regulating the structural and functional characteristics of Pd/Al 2O 3-catalysts (applied on ceramic monoliths of honeycomb structure) of nitrogen oxide reduction by methane. Modifying additives provide increase of thermal stability of porous structure of both highly dispersed Al 2O 3, as the second support, and the catalyst as a whole. Contribution of La2O3 and CeO2 in increasing the thermal stability is of an additive nature, and lanthanum oxide shows the higher efficiency than cerium one. According to X-ray phase analysis data, stabilizing action is conditioned by occurrence of rare-earth element oxides into lattice of Al2O3, which retards diffusional processes leading to phase transitions of low-temperature crystalline modifications of alumina into high-temperature ones with a low specific surface. For the catalyst samples modified with La2O3 an effect of thermal activation is observed, which is revealed by increase in catalytic activity as a result of annealing at 850 °C. Such a phenomenon, as shown by means of X-ray photoelectron spectroscopy technique, can be explained via stabilization of palladium in singly charged state in the form of groups of Pd+O2− and corresponding increase in concentration of active centers. 相似文献
18.
A vacuum-annealed La 0.6Ca 0.4CoO 3−x was consecutively oxygenated in air at temperatures decreasing from 800 to 100 °C, and its electrocatalytic activities for oxygen reduction and evolution were then measured as a function of the oxygenation temperature. The valence of Co cation, changing between +2 and +3, was found susceptible to annealing either in vacuum or air. The catalytic activities initially decrease monotonically as the oxygenation temperature was decreased from 800 to 300 °C, as a result of increasing oxygen content, and then rise abruptly with the oxygen reduction activity reaching a maximum at 200 °C and the oxidation activity at 150 °C. X-ray photoelectron spectroscopy analysis indicated that the enhancements by the low-temperature oxygenation involved increased OH coverage and less charged cations at surface. The results clearly reveal the importance of the post-calcination annealing process for optimizing the performance of La 0.6Ca 0.4CoO 3−x in air electrode applications. 相似文献
19.
Laboratory experiments were conducted using a rotating cylinder electrode apparatus to study the effect of solution hydrodynamics on the deposition of calcium sulfate scale on stainless steel substrate. The results indicate that the solution hydrodynamics has a significant bearing on the deposition rate of calcium sulfate. The results are in agreement with the theoretical prediction of a diffusion controlled process. Furthermore, scanning electron microscopy revealed the secondary nucleation growth of prismatic needle- or rod-like crystals branching out randomly over the already existing primary crystals of CaSO 4 on the SS-316 substrate. 相似文献
20.
The catalytic activity of a mixed phase of copper–cobalt and copper–manganese oxides supported on magnesium fluorine or alumina has been studied in low temperature CO oxidation at 30 °C. During calcination, the oxides studied partially react to form different type spinels depending on the calcination temperature. These spinels have different effect on the catalytic activity. In low temperature CO oxidation the copper–manganese catalysts are more active than the copper–cobalt ones. 相似文献
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