Conventional Solid Electrode Research Articles

Electrochemical lithium extraction with continuous flow electrodes

Electrochemical lithium extraction presents the advantages of superior ion selectivity and environmental friendliness. However, it faces challenges of intermittent operation, limited areal capacity and constrained mass transfer with conventional solid electrodes. In this work, we propose a continuous electrochemical lithium extraction system by using flow electrodes. Due to the inherent fluidic characteristics, the flow electrodes facilitate efficient mass transfer, thereby manifesting boosted kinetics in the insertion and extraction of lithium ions. Compared with solid electrodes, flow electrodes exhibit a substantial augmentation in lithium extraction capacity, demonstrating a nearly sixfold increase in simulated Atacama brine and a nineteen-fold in diluted Atacama saline under equivalent current density. Furthermore, we achieve a lithium production rate of 1 mol m−2 h−1 with a purity level of 0.97 at a high current density of 4 mA cm−2. These results exemplify the capability of flow electrodes for industrial-scale lithium extraction, particularly emphasizing their suitability for large-scale and high-speed production.

Development of an endothermic electrode for electroporation-based therapies: A simulation study

Cell death mediated by non-thermal mechanisms is an essential characteristic of irreversible electroporation for tumor ablation. However, needle electrodes inherently promote thermal damage immediately adjacent to the electrode/tissue interface, especially in cases when intensive pulsed electric fields are applied to get a large ablation. In this study, we propose utilization of endothermic reactions in the core of clinically used needle electrodes to absorb the heat generated during electroporation, thereby accentuating the nonthermal aspect of irreversible electroporation. In this study, numerical models were developed to determine temperature profiles resulting from a typical irreversible electroporation (IRE) protocol in clinic using either conventional solid electrodes or hollow electrodes filled with NH4NO3 to facilitate an endothermic reaction in the electrode core. The results indicate that the endothermic electrodes can reduce the temperature rise and thermal damage during IRE treatment.

Characteristics of resistance spot welding using annular recess electrodes

Resistance spot welding is widely used in manufacturing industries, such as automobile structural body manufacture, rail vehicle construction, electronics manufacture, battery manufacture, etc. Resistance spot weld integrity is of paramount importance in the manufacturing industry, especially in automotive body joining to ensure that the automobile bodies can withstand the stress levels that the vehicle is subjected in operation. A number of factors - including electrode geometry, electrode force, welding current and welding time - influence the quality of the resistance spot weld. The electrode material that ensures electrical conductivity and compressive strength and electrode geometry defined by the electrode tip profile, shape, size are important factors in resistance spot welding. This paper discusses the comparative performance of resistance spot welding electrodes with annular recess design and the conventional solid design in welding of a 1 mm thick steel sheet used in construction of automobile structural bodies. The copper-based electrodes used in this study were prepared as described in the ISO 5182:2008 Standard. The annular recess electrode was designed using SolidWorks Version 2015; a hole measuring 4 mm deep and 2.50 mm in diameter was created centrally on the electrode tip and filled with heat resistant mixture of cement and kaolin ceramics. The effects of applied electrode force, current, and weld time on weld-integrity were investigated for the two designs of resistance spot welding electrodes. Linear regression analysis of data obtained established that the weld strength and nugget diameter was higher for the annular recess electrode than the conventional solid electrode. An analysis of variance established that the observed variation of the nugget diameter with weld time was statistically significant but the variations of weld strength with applied electrode force and variation of nugget diameter with current were not statistically significant which may require further study.

Differential Alternative Pulses Voltammetry Application in Organic and Inorganic Analysis

The simultaneous voltammetric determination of species with close peak potentials presents some difficulties, because of the overlapping of their redox peaks at conventional solid electrodes. Therefore, two approaches were proposed to overcome this drawback: (i) chemometric resolution of the overlapped peaks by semi-derivative or multivariate analysis and (ii) development of chemically modified electrodes with better electrochemical performances, permitting peaks separation. However, the mathematical treatment habitually results in a precision decrease, while the electrode modification often requires the use of expensive materials and involves sophisticated techniques. Hence, another strategy for the direct simultaneous species determination is suggested in this work. It involves the application of Differential Alternative Pulses Voltammetry (DAPV) [1], which provides the great resolution of the second order voltammetric techniques, as Radio-Frequency Polarography, Second Harmonic AC Voltammetry, and Differential Faradaic Rectification Polarography (DFRP), in combination with the high sensitivity, precision, and instrumental and operational simplicity of the most common voltammetric technique, the differential pulse voltammetry (DPV).The second order voltammetric techniques including DAPV are based on the nonlinearity of the electrochemical system I/E characteristic yielding voltammograms shaped as a derivative of voltammetric peak resulting from small sinusoidal or rectangular bipolar deviations of the DC potential. Two single pulses of small amplitude, one cathodic and one anodic are successively applied in DAPV for every value of the scanned DC potential with delay time between the pulses equal to the delay time between the scan step and the first one (Fig. 1). The sum of the two pulse faradaic current components with opposite polarities is registered vs. the scanned potential as DAPV voltammogram. The experimentally determined half-width of the DAPV peaks (37 mV at 2 electrons reduction) is 1.22 times smaller than that of the most common voltammetric technique DPV (45.3 mV) at the same conditions and equals that obtained by the application of another second order technique, the DFRP. Thus, the DAPV voltammogram’s shape as second derivative of voltammetric wave combined with the small half-widths of the anodic and the cathodic peaks allows simultaneous quantification of species having very small peak potential difference.Taking advantage from the great resolution power of DAPV, it was applied for the simultaneous determination of a range of organic (catechol and hydroquinone [2]; o-nitrophenol, m-nitrophenol and p-nitrophenol [3]) and inorganic species (Cd2+/In3+; Tl+/Pb2+ [1, 4]) with close peak potential difference, as shown in Figs. 2-5.The proposed approach offers a very simple alternative route for the simultaneous determination of a broad range of species and overcomes the disadvantages of the currently applied strategies involving electrode modification or mathematical data processing.

Sulfur Vapor-Infiltrated 3D Carbon Nanotube Foam for Binder-Free High Areal Capacity Lithium–Sulfur Battery Composite Cathodes

Here, we demonstrate a strategy to produce high areal loading and areal capacity sulfur cathodes by using vapor-phase infiltration of low-density carbon nanotube (CNT) foams preformed by solution processing and freeze-drying. Vapor-phase capillary infiltration of sulfur into preformed and binder-free low-density CNT foams leads to a mass loading of ∼79 wt % arising from interior filling and coating of CNTs with sulfur while preserving conductive CNT-CNT junctions that sustain electrical accessibility through the thick foam. Sulfur cathodes are then produced by mechanically compressing these foams into dense composites (ρ > 0.2 g/cm3), revealing specific capacity of 1039 mAh/gS at 0.1 C, high sulfur areal loading of 19.1 mg/cm2, and high areal capacity of 19.3 mAh/cm2. This work highlights a technique broadly adaptable to a diverse group of nanostructured building blocks where preformed low-density materials can be vapor infiltrated with sulfur, mechanically compressed, and exhibit simultaneous high areal and gravimetric storage properties. This provides a route for scalable, low-cost, and high-energy density sulfur cathodes based on conventional solid electrode processing routes.

Rapid Determination of Uranium in Water Samples by Adsorptive Cathodic Stripping Voltammetry Using a Tin-Bismuth Alloy Electrode

In this work, the tin-bismuth alloy electrode (SnBiE) was used for U(VI) concentration determination for the first time. Compared to the conventional solid electrode (glassy carbon electrode and bismuth bulk electrode), the SnBiE possesses a higher hydrogen overpotential, which indicates that the tin-bismuth alloy can considerably extend the application of potentially available electrode detection systems. Combining with electrochemical behavior analysis and spectrometric measurements as well as theoretical calculation methods, the geometric structures of uranium-cupferron (N-nitrosophenylhydroxylamine) complexes have been revealed and a more detailed electrode mechanism has been proposed. The electroanalysis results show that the optimal sensitivity could be obtained by using diphenylguanidine as the auxiliary reagent. The calibration plot for U(VI) quantification was linear from 0.5nM to 30nM with a correlation coefficient of 0.999. In the meanwhile, a detection limit of 0.24nM was obtained in connection with an accumulation time of 30 s, which is comparable with that of mercury analogues. The practical applications of SnBiE have been tentatively performed for the determination of UO22+ in real water samples and the results were well consistent with those by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). A very simple, convenient and cheap approach was established for the determination of UO22+ in natural water samples containing surfactants without the otherwise necessity of sample pretreatment, which drastically reduce the analysis time.

Use of wire bunch electrodes in electric discharge machining

PurposeIn electrical discharge machining (EDM) process, the production of separate electrodes for rough, semi‐rough and finish machining of dies and moulds having complex surfaces, results in high cost and long lead‐time in manufacturing. The purpose of this paper is to describe the machining performance of electrodes formed by using copper wire bunches (WBs) positioned to conform the surface to be machined was experimentally and theoretically analyzed. In the study, the variations in the machining rate, electrode wear rate, relative wear and workpiece surface roughness were examined for various discharge current and pulse‐time settings.Design/methodology/approachCopper WBs positioned to conform the surface to be machined in electric discharge machining. The variations in the machining rate, electrode wear rate, relative wear and workpiece surface roughness were examined experimentally for various discharge current and pulse‐time settings. The WB electrodes (WBEs) are proven to be satisfactory as electrodes for roughing operations in electric discharge machining.FindingsThe increase in number of wires and pulse energy result in decrease of relative wear for each wire in the electrode. The increase in number of wires in electrodes causes increase in machining area and in machining time in WBE method. With the increase of discharge current and pulse time, the electrode wear rate and material removal values increase and machining time decreases. By using the mathematical models obtained from the result of the experiments, the electrode wear rate, material removal rate, relative wear and the set length of wires for the desired cavity profile can be calculated. The labor cost of electrode manufacturing in the WBE method is lower compared to conventional solid electrodes. The use of WBE method for rough machining decreases machining cost and time. The use of WBE method decreases both the number of the electrodes required and the delay in starting machining due to the preparation of electrode in EDM.Originality/valueThis paper introduces the benefits of using WBE in electric discharge machining; wear and material removal characteristics of WBEs are introduced; the surface roughness characteristics of surfaces produced by WBEs are examined experimentally; and the effect of number of wires used in WBEs given (experimental findings).

A novel nanoporous gold modified electrode for the selective determination of dopamine in the presence of ascorbic acid

The electrochemical detection of dopamine (DA) at conventional solid electrodes was interfered by the coexisted ascorbic acid (AA). To circumvent this problem, many modified electrodes were tried. In this paper, an attempt was made to use nanoporous gold (NPG) as modifying materials. The NPGs with different pore sizes were prepared simply by dealloying Ag from Au/Ag alloy with concentrated nitric acid. The glassy carbon electrode (GCE) based modified electrode was fabricated by simply affixing the NPG film on the surface of a GCE. The electrochemical behaviors of AA and DA at the modified electrode were studied. The results indicated that the NPG/GCE exhibited substantial enhancement in electrochemical sensitivity for DA and AA due to its large surface area. Results also showed that the oxidation of AA at the electrode was a diffusion-controlled process, but for DA it was an adsorption-controlled process. This result, together with the different anodic peak potentials of the two species, made it possible the selective determination of DA in the presence of AA. Due to the interaction of the amino group of DA with the surface of nanoscale gold, DA could be accumulated on the NPG/GCE, while AA could not. This permitted the coexistence of large amount of AA. When differential pulse voltammetry (DPV) was used, a submicrolevel of DA could be detected in the millimolar level of AA with a detection limit of 17 nM at a signal-to-noise ratio of 3. In a word, the modified electrode showed good sensitivity, selectivity and reproducibility.

Ionic liquids as green electrolytes for the electrodeposition of nanomaterials

Ionic liquids, especially air and water stable ones, experience much attention, since they have attractive physical properties. We exemplify in this paper the potential of ionic liquids in the electrodeposition of nanocrystalline metals without additives. The results show that nanocrystalline copper and aluminium can be electrodeposited in the air and water stable ionic liquids 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([BMP]TFO) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP]Tf2N), respectively, on conventional solid electrodes with sufficient electronic conductivity. Generally, the obtained Al or Cu deposits are shiny, dense and adherent with very fine crystallites with average sizes of about 30 and 40 nm, respectively. The [BMP]+ cation might act as a grain refiner, leading to nanosized deposits. The results of first attempts to use plasmas as mechanically contact-free electrodes for the cathodic deposition of nanoscaled metals (glow discharge electrodeposition) are also presented. The relevance of our results for the development of a green process to make nanomaterials as catalysts for fuel processing is briefly discussed.

Carbon Powder Based Films on Traditional Solid Electrodes as an Alternative to Disposable Electrodes

AbstractThe covering of conventional solid electrode with a film using an ink containing a conductive powder and a polymer enables to broaden the potential window of the original solid electrode. A solid silver amalgam electrode covered with such a film exhibits a potential window from −600 mV to +1400 mV vs. SCE reference electrode. The renewal of the film is fast and simple: the electrode can be simply wiped with a filter paper to remove the old film and immersed into an ink solution or 1–2 μL of this ink solution can be applied to the surface of the electrode with a micro dispenser to form a new film. Therefore, just the inexpensive film at the electrode surface is disposable and there is no need to dispose the whole, more expensive electrode. Moreover, when a suitable electrochemical pretreatment of the film electrode is applied, the same film can be used for reproducible measurements for several days.

Spectroscopic and Electrochemical Study of a Tetrapyridylporphyrin Modified with Four Bis-(1,10-phenanthroline)chlororuthenium(II) Complexes

A new modified tetrapyridylporphyrin symmetrically coordinated to four [ Ru ( phen )2 Cl ]+ groups has been synthesized and its structural and electrochemical properties have been investigated by means of 1 H and COSY NMR, UV-vis and luminescence spectroscopy, cyclic voltammetry and spectroelectrochemistry. The presence of the phenanthroline ligands has improved the stability of the molecular films generated on the surface of conventional solid electrodes in comparison with the analogous bipyridine derivative. The performance of the modified electrodes has been evaluated for the detection of dopamine, with excellent results.

Continuous-flow column electrolytic spectroelectrochemistry for two-step one-electron transfer reactions

Abstract Mathematical treatments of continuous-flow column electrolytic spectroscopy for the two-step one-electron transfer reaction are presented. The relationship between the absorbance and the apparent number of electrons in electrolysis, which is independent of electrolytic efficiency, is useful for the analysis of quasi-reversible as well as reversible redox reactions. The theory has been applied to the analysis of the redox reaction of 9,10-anthraquinone-2,7-disulfonate, which exhibits totally reversible characteristics in continuous-flow column electrolysis and also in cyclic voltammetry at a column electrode in stationary solution. The redox potentials of the two successive electron transfers and the absorption spectra of the semiquinone intermediate in aqueous solution have been successfully determined. The redox reaction of 2,6-dimethyl-1,4-benzoquinone, which is irreversible (or quasi-irreversible) in cyclic voltammetry at a conventional solid electrode, has also been characterized from the thermodynamic aspects.

Stripping voltammetry of copper and lead using gold electrodes modified with self-assembled monolayers

One problem associated with using bare solid metal electrodes, such as gold and platinum, in stripping analysis to determine heavy metal ions such as lead and copper ions in dilute solutions is that underpotential deposition (UPD) gives multiple stripping peaks in the analysis of mixtures. These peaks are often overlapped and cannot be conveniently used for analytical purposes. Bifunctional alkylthiols, such as 3-mercaptopropionic acid, with an ionizable group on the other terminal end of the thiol can form self-assembled monolayers (SAMs) on the surface of the gold electrode. It is shown that such an SAM-modified gold electrode minimizes the UPD effects for the stripping analysis of lead and copper. The anodic peak potential shifts and the peak shape changes, indicating that the SAM changes the deposition and stripping steps of these heavy metal ions. Thus, the sensitivity levels for both single species and mixtures can be significantly improved for the conventional solid electrodes. The mechanism of the deposition reaction at the SAM-modified gold electrodes is discussed.

Electrode architecture related to surface flashover of solid dielectrics in vacuum

A lateral test structure with metalized film electrodes is shown to have distinct advantages over a conventional solid electrode structure for studying the HV characteristics of solid insulators in vacuum. The paper presents results of streak photography and spectral analysis of surface discharge luminosity, and of preflashover activity using time-coordinated current, luminosity, and imaging of light activity emanating from the surface of the stressed dielectric. The preflashover activity, consisting of bursts of time-correlated current and light emission, is associated with randomly distributed emission spots on the surface. It is proposed that the above observations are related to charge trapping and detrapping processes at localized energy levels associated with insulator surface defects.

Electrochemistry at the tetrathiafulvalene‐tetracyanoquinodimethane electrodes. Application to the study of c‐type cytochromes

AbstractElectrodes made from pastes of the conducting organic salt, tetrathiafulvalene‐tetracyanoquinodimethane (TTF‐TCNQ), are prepared and characterized using electrochemical techniques. These electrodes behave as conventional solid electrodes within their stable potential range. An attractive property is their capability to achieve direct electrochemistry of c‐type cytochromes (horse heart cytochrome c, cytochrome c552 from Thiobacillus ferrooxidans). Resuits on pH‐dependence and kinetic data for these metalloproteins agree with previously published data. It is suggested that favorable interactions occur between the TTF‐TCNQ electrode surface and redox protein sites. Moreover, the analytical advantage of using permselective‐membrane TTF‐TCNQ electrode is demonstrated.