Electrode Processes Research Articles

Degradation of Styrene-Poly(ethylene oxide)-Based Block Copolymer Electrolytes at the Na and K Negative Electrode Studied by Microcalorimetry and Impedance Spectroscopy

The electrode-electrolyte interface of alkali metal electrodes and solid polymer electrolytes (SPE) is challenging to access because solid electrolytes are difficult to remove without damaging the interphase region. Herein, the two non-invasive techniques isothermal microcalorimetry (IMC) and electrochemical impedance spectroscopy (EIS) are combined to explored degradation processes of reactive sodium and potassium metal electrodes in contact with SPEs. Comparison of the parasitic heat flows and interfacial resistances at different current densities with a liquid electrolyte (LE) system showed marked differences in aging behaviour. The data also suggest that the electrochemically active surface area of alkali metal electrodes increase with cycling, leading to larger parasitic heat flows and indicating morphological changes. SPE-based cells exhibit similar levels of parasitic heat flow at different current densities, which is in stark contrast to the LE cell where a strong correlation between the two is evident. The ambiguity of EIS spectra is challenging due to the overlapping time constants of the underlying electrode processes. However, equivalent circuit modelling can be used to follow trends in resistance evolution, for example to track the rapidly increasing cell impedance in K/K symmetric cells during a 48 h equilibration interval prior to cycling, which abruptly disappeared once cycling begins.

Improved performance in quantum-dot light-emitting diodes through current annealing

The impact of metallic diffusion, stemming from the thermal evaporation process of electrodes, exerts a substantial influence on solution-processed quantum-dot light-emitting diodes (QD-LEDs). This study highlights a significant enhancement in the performance of QD-LEDs achieved through post-metal-evaporation current annealing. The choice of different metal electrodes emerges as a critical factor affecting QD-LED performance during current annealing. In the case of red QD-LEDs with an Al cathode, the maximum external quantum efficiency (EQE) surged from 7.0% to an impressive 14.1%. Conversely, QD-LEDs with an Ag cathode exhibited a more modest improvement, progressing from 10.8% to 12.4%. Notably, an Al/Ag composite electrodes demonstrated the potential for further enhancement, achieving a remarkable maximum EQE of 18.3%. The observed performance improvements can be attributed to the formation of metal diffusion-induced Al-doped ZnO, facilitating electron injection, and Al-oxidized passivated quantum dots (QDs), effectively mitigating metal-induced quenching following current annealing. This study conclusively demonstrates that the application of current annealing can effectively counteract the adverse effects of metal diffusion in QD-LEDs, presenting itself as a promising method for elevating the overall performance of quantum-dot light-emitting diodes.

In English

The total reorganization energy of the system and its components, the solvent reorganization energy and the transformation energy of reactants (water clusters [(H2O)nOH]-), during electrocatalytic hydrogen evolution on binary alloys of molybdenum with iron subgroup metals (Fe, Co, Ni) in an alkaline medium (30 wt. % NaOH solution) have been calculated. The calculated values of the solvent reorganization energy and the reorganization energy of water clusters are in agreement with the Marcus – Dogonadze – Kuznetsov theory. The dependence of the total reorganization energy of the system, the solvent reorganization energy, and the reorganization energy of discharging species (water clusters) on the electrolyte temperature has been calculated. It was shown that the total reorganization energy of the system and the activation energy of the electron-transfer reaction of electrocatalytic hydrogen evolution (HER) on binary alloys of molybdenum with iron subgroup metals in an alcaline vedium (30 wt. % NaOH solution) decrease linearly with increasing electrolyte temperature in the following order: Fe-54 at. % Mo > Ni-54 at. % Mo > Co-52 at. % Mo. The temperature dependences of the water cluster discharge reorganization energy and the activation energy on binary molybdenum alloys are linear and intersect in the boiling point region of 30 wt. % NaOH solution 384.7 K. At this temperature, the electrode process is limited by the diffusion of regenerating water clusters to the electrode surface. The calculated diffusion activation energy Ad is 9.9 kJ·mol–1. The value of the system reorganization energy lt is 39.8 kJ·mol–1, which is consistent with the theory of Markus – Dogonadze – Kuznetsov. Electrocatalytic activity of binary alloys of molybdenum with iron subgroup m

Effect of atomization amounts on electrical discharge ablation machining and electrochemical machining

ABSTRACT This study investigated the impact of varying atomization amounts on composite machining involving both atomized electrical discharge ablation machining and electrochemical machining (EDAM-ECM). Additionally, this study examined the effects of different atomization amounts on the material removal rate, relative electrode wear rate, processing waveforms, surface roughness, surface morphology and elements, and the EDAM-to-ECM ratio. Moreover, a theoretical model for describing the material removal process in composite processing was developed. Furthermore, the effect of the ECM ratio on the processing results was quantitatively analyzed through the integration of statistical circuits with a formula for calculating recast layer thickness. The model was used to predict and select the optimal atomization amounts required to achieve recast layer removal during processing. The results revealed that at an atomization amount of 200 mL/min, 16.7% of the total material removal was attributable to ECM, indicating the successful removal of the recast layer. At this atomization amount, the fabricated sample maintained a machining precision of 0.02 mm.

Electrochemical oxidation of low concentrated tetracycline (TC) in aqueous solution: Operation optimization, degradation mechanisms, and detoxification efficiency

The three-dimensional electrode (3DE) process has attracted much attention due to its high efficiency in treating hard-to-degrade organic pollutants. In this work, an efficient removal of low-concentration tetracycline (TC) from aqueous solution was achieved using a 3DE reactor equipped with IrO2-RuO2-Ti anode and granular activated carbon (GAC). In addition, the reliable response surface model (RSM) indicates that maintaining a current density of 12.5 mA/cm2 led to effective TC degradation (≥ 96%) within two hours. After verification, •OH and •O2− were identified as the primary active oxygen species in the 3DE system and the addition of particle electrodes significantly enhanced the system's ability to generate •O2−. Additionally, we proposed the complete degradation pathway for TC in the 3DE system, utilizing LC-MS and DFT calculations. Notably, the 3DE system demonstrates superior detoxification efficiency. Many highly toxic intermediates detoxify into minimal amounts of less toxic substances after degradation and exhibit a growth-promoting ability for mung beans comparable to that of pure water. Meanwhile, the outstanding universality, stability, and cost-effectiveness of 3DE systems also contribute to its extensive application prospects. The study presents an efficient, cost-effective, and viable process scheme for removing low-concentration TC from aqueous solutions.

Assessment of captan pesticide stability by thermal and spectroelectrochemical analysis

In this study, thermal analysis and electrochemical methods were used to evaluate the stability of captan pesticide (CPTN). Simultaneous Thermogravimetry (TG), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) were successfully applied to study the stability of CPTN in the temperature range from 20 to 600 °C. The stability evaluation of CPTN by spectroelectrochemical analysis was carried out using cyclic voltammetry (CV) and electrolysis at constant current density in association with UV−Vis spectrophotometry. Thermoanalytical results revealed a relative stability of CPTN up to a temperature of 154 °C, and above this temperature the pesticide molecule undergoes irreversible degradation. The kinetic approach of the electrochemical results on the electrochemical degradation of CPTN showed a rate constant of 0.02 min−1 in the presence of chloride ions and 0.089 min−1 in the presence of bromide ions. Thermal and electrochemical methods are considered effective strategies applied in order to eliminate pesticides from polluted waters, and the choice of optimal parameters can considerably increase the efficiency of decontamination. The study also aims to provide insights into electrode processes to address the mechanism of electrochemical degradation.

Investigation of hydrogen generation from the reaction of beryllium pebbles with water vapor for WCCB-TBM

Be pebble, as a neutron multiplier material, is being explored for the development of a Water-Cooled Ceramic Breeder Test Blanket Module (WCCB-TBM) in Japan for the International Thermonuclear Experiment Reactor (ITER) project. The Be pebbles were fabricated by the rotating electrode process (REP). However, as the safety of the test blanket module (TBM) could be compromised by hydrogen generation via Be–H2O reaction owing to the leakage of pressurized water from the cooling pipes inside TBM, the safety assessment of TBM must be conducted using the Be–H2O reactivity data for the Be pebbles whose fabrication method is the same as that for TBM (i.e., REP). Thus, in this study, a Be–H2O reactivity test was conducted using Be pebbles that were fabricated by REP to characterize the generated hydrogen and evaluate the hydrogen generation (HG) rates toward WCCB-TBM safety assessment. First, the Be–H2O reactivity data were obtained at ≥ 300 °C (the coolant temperature for the TBM). The experimental results and oxidation rate of the Be pebbles revealed that only the Be surface may have been oxidized at 300 °C–600 °C, although its inside was oxidized at 700 °C–1000 °C. Further, the experimental data–derived HG rates at 300 °C–1000 °C increased with the temperature and the tendency changed in the three temperature regions. The HG rates did not contradict those reported by previous studies. Additionally, these regions corresponded to each expected Be–H2O reaction behavior at 300 °C–1000 °C. At a Be temperature of < 600 °C, the generated hydrogen from TBM will not exceed 2.5 kg of a limitation by the water leakage on the estimation based on the HG rates and the qualitative effects of the safety functions.

Effect of MXene Nanosheet Sticking on Supercapacitor Device Performance

Supercapacitors have garnered significant interest in recent years due to their high power density, rapid charge/discharge rates, and long cycle life. MXenes, a family of two-dimensional (2D) transition metal carbides/nitrides, have emerged as promising electrode materials for supercapacitors. However, one major challenge associated with incorporating MXenes in supercapacitor structures is the occurrence of sticking, wherein individual MXene flakes agglomerate, leading to reduced electrode performance. This review paper discusses various causes of sticking and approaches to preventing it, offering insights into the design and development of high-performance MXene-based supercapacitors. The morphology and size of MXene flakes, flake surface chemistry, thickness, surface area/volume ratio, electrode processing techniques (including solvent selection, additives incorporation, and deposition technology), and environmental factors were shown to be the basic factors resulting in sticking of MXene sheets. Among the strategies to mitigate this challenge, surface functionalization and passivation, integration with polymer matrices or carbon nanomaterials, and electrode processing optimization were considered. Possible paths for optimization and future directions of study, such as novel MXene compositions, understanding of interfaces and electrode–electrolyte interactions, development of advanced electrode architectures, and integration of energy storage systems, were assumed.

High-Quality Spherical Silver Alloy Powder for Laser Powder Bed Fusion Using Plasma Rotating Electrode Process.

The plasma rotating electrode process (PREP) is an ideal method for the preparation of metal powders such as nickel-based, titanium-based, and iron-based alloys due to its low material loss and good degree of sphericity. However, the preparation of silver alloy powder by PREP remains challenging. The low hardness of the mould casting silver alloy leads to the bending of the electrode rod when subjected to high-speed rotation during PREP. The mould casting silver electrode rod can only be used in low-speed rotation, which has a negative effect on particle refinement. This study employed continuous casting (CC) to improve the surface hardness of S800 Ag (30.30% higher than mould casting), which enables a high rotation speed of up to 37,000 revolutions per minute, and silver alloy powder with an average sphericity of 0.98 (5.56% higher than gas atomisation) and a sphericity ratio of 97.67% (36.28% higher than gas atomisation) has been successfully prepared. The dense S800 Ag was successfully fabricated by laser powder bed fusion (LPBF), which proved the feasibility of preparing high-quality powder by the "CC + PREP" method. The samples fabricated by LPBF have a Vickers hardness of up to 271.20 HV (3.66 times that of mould casting), leading to a notable enhancement in the strength of S800 Ag. In comparison to GA, the S800 Ag powder prepared by "CC + PREP" exhibits greater sphericity, a higher sphericity ratio and less satellite powder, which lays the foundation for dense LPBF S800 Ag fabrication.

Oxygen reduction reaction induced electrode effects in polymer light-emitting electrochemical cells

The perceived diminished sensitivity of Polymer Light-Emitting Electrochemical Cells (LECs) to electrode material and active layer thickness compared to Organic Light-Emitting Diodes (OLEDs) due to electrochemical doping, positions them as a focal point in emerging electronic applications. However, empirical evidence reveals the electrode still influences device performance. Simultaneously, electrochemical doping involves side reactions at the cathode, predominantly with oxygen. Nevertheless, the impact of oxygen reduction reaction on the device performance concerning electrode effects remains underexplored. This study centers on the pivotal influence of oxygen reduction reaction on the electrode effect in LECs. The investigation of the doping process for various electrodes and active layer thicknesses was conducted using photoluminescence imaging. Through controlling temperatures and vacuum levels, obtained time-current curves undergo fitting procedures, which enables quantitative analysis of oxygen reduction reaction effects on both electrode and film thickness. The results underscore the impact of oxygen reduction reaction on the performance of the device induced by electrodes, emphasizing the pronounced effect on the activation energy of the reduction reaction dictated by both the electrode work function and oxygen concentration. In addition, this study elucidates that the utilization of a low-work-function bottom contact in conjunction with a thicker active layer exerts a discernible influence on the device's current magnitude.

Enhancing Sr-deficient Sr(Ti0.3Fe0.7)O3–δ Cathode Performance through Sm0.5Sr0.5CoO3–δ Infiltration

The development of cathodes with improved polarization, aimed at reducing the operating temperature of solid oxide fuel cells (SOFCs), is an important avenue of research toward more efficient SOFCs. Sr(Ti0.3Fe0.7)O3–δ recently emerged as an active and stable cathode material; although its oxygen transport capability was shown to be further improved by introducing a Sr deficiency, the accompanying increased sinterability creates challenges in optimizing cathode microstructure. One facile approach may be single-step infiltration with highly active materials, such as Sr0.5Sm0.5CoO3–δ (SSC). However, there is limited knowledge regarding the impact of SSC on the electrochemical mechanisms within Sr-deficient Sr(Ti0.3Fe0.7)O3–δ . In this study, we systematically investigate the electrochemical characteristics of SSC-infiltrated Sr0.95(Ti0.3Fe0.7)O3–δ (STF) cathodes. Transmission line model-based impedance analysis provides a mechanistic understanding of STF and the role of SSC infiltrants in polarization improvement. The results reveal that SSC effectively reduces the resistance associated with key electrode processes, including oxygen diffusion, surface exchange, and dissociative adsorption/desorption. Consequently, using SSC infiltration, the power density of a Ni–Zr0.84Y0.16O2–δ (YSZ) anode-supported full cell with thin (∼2.5 μm) electrolyte increased from ∼1.88 to ∼2.47 W cm–2 at 800 °C.

Catalysis of Indium Ion Electroreduction in the Presence of Acetazolamide in Chlorates(VII) Solutions with Varied Water Activity.

The influence of acetazolamide (ACT) on the kinetics and the mechanism of electroreduction of In(III) ions as a function of changes of the water activity was investigated using electrochemical methods (DC, SWV, CV and EIS, CV). The multi-step mechanism of the electroreduction process should take into account the dehydration step of indium ions and the presence of In-ACT (,,cap-pair" effect) active complexes, mediating electron transfer, located in the adsorption layer. Differences in the electrode mechanism in the presence of ACT were observed for higher chlorates(VII) concentrations (above 4 mol ⋅ dm-3 chlorates(VII)) reflected by a lack of step wise nature of the electrode process. The highest catalytic activity was observed in 4 mol ⋅ dm-3 chlorates(VII).

Design and fabrication of wearable electronic textiles using twisted fiber-based threads.

Mono-dimensional fiber-based electronics can effectively address the growing demand for improved wearable electronic devices because of their exceptional flexibility and stretchability. For practical applications, functional fiber electronic devices need to be integrated into more powerful and versatile systems to execute complex tasks that cannot be completed by single-fiber devices. Existing techniques, such as printing and sintering, reduce the flexibility and cause low connection strength of fiber-based electronic devices because of the high curvature of the fiber. Here, we outline a twisting fabrication process for fiber electrodes, which can be woven into functional threads and integrated within textiles. The design of the twisted thread structure for fiber devices ensures stable interfacing and good flexibility, while the textile structure features easily accessible, interlaced points for efficient circuit connections. Electronic textiles can be customized to act as displays, health monitors and power sources. We detail three main fabrication sections, including the fabrication of the fiber electrodes, their twisting into electronic threads and their assembly into functional textile-based devices. The procedures require ~10 d and are easily reproducible by researchers with expertise in fabricating energy and electronic devices.

On the Origin of Anode and Cathode Contributions to the Impedance of All‐Solid‐State Batteries

AbstractAll‐solid‐state‐batteries (ASSBs) are considered as promising next‐generation batteries in order to achieve improvements in both energy density and safety. The complex electrochemical processes in ASSBs taking place on different time scales can be probed by means of electrochemical impedance spectroscopy. However, the separation of anode and cathode contributions to the impedance and the understanding of the underlying electrochemical processes in both electrodes is a challenging task. Here, we compare the impedance spectrum of a prototypical full ASSB to those of symmetric cells anode | separator | anode and cathode | separator | cathode. We use Ni‐rich polycrystalline LiNi0.85Co0.10Mn0.05O2 particles as active material inside the composite cathode and an indium‐lithium alloy as anode. Based on the comparison, we show that the charge transfer process inside the cathode is remarkably fast, i. e., even faster than observed for cathodes of batteries with liquid electrolyte. Our results give indication that the differences in the time scales of cathode and anode processes are related to the distinct transport properties of interphases inside the cathode and at the anode | separator interface, respectively.

Voltammetric determination of genotoxic 4‐nitroindane at a mercury meniscus modified silver solid amalgam electrode

AbstractA silver solid amalgam electrode modified with mercury meniscus (m‐AgSAE) was used as a non‐toxic replacement of mercury electrodes in the voltammetric determination of genotoxic environmental pollutant 4‐nitroindane (4‐NI). The m‐AgSAE was used to characterize of the overall electrode process during the 4‐NI conversion using cyclic voltammetry (CV), and it was shown that the electrochemical reduction of 4‐NI is an irreversible process controlled by both diffusion and adsorption. Techniques of direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at the m‐AgSAE were optimized for the development of a method for the sensitive determination of 4‐NI. The application of the more convenient DPV method was proven on authentic drinking and river water samples. Limits of quantification (LQs) obtained under the following optimal conditions were 0.1 μmol L−1 for DCV at the m‐AgSAE (Britton‐Robinson (BR) buffer pH 5.0–methanol (1 : 1); regeneration potentials E1,reg=−200 mV, E2,reg=−1100 mV) and 0.1 μmol L−1 for DPV at the m‐AgSAE (BR buffer pH 9.0–methanol (1 : 1); regeneration potentials E1,reg=−300 mV, E2,reg=−1300 mV). An attempt to decrease the LQ of the 4‐NI determination by differential pulse adsorptive stripping voltammetry at the m‐AgSAE was not successful. The LQs for DPV at the m‐AgSAE in authentic samples of drinking and river water were 1.0 μmol L−1 and 2.0 μmol L−1 (BR buffer pH 9.0–drinking or river water (1 : 9); regeneration potentials E1,reg=−300 mV, E2,reg=−1300 mV), respectively.

Revisiting the Butler-Volmer Electrode Kinetics: Separating the Anodic and Cathodic Current Components of a Quasi-Reversible Electrode Reaction in Staircase Voltammetry

A simple mathematical strategy is proposed to estimate anodic and cathodic current components in voltammetry by combining the basic mathematical model of a quasi-reversible electrode reaction at a conventional planar electrode with the Butler-Volmer electrode kinetics with a goal to simplify and facilitate the measurement of electrode kinetics. In spite of the fact that the separate anodic and cathodic current components are experimentally inaccessible parameters, it is demonstrated for the first time that they can be reliably estimated from the net (total) current over the whole potential interval of a common voltammetry, requiring only the current–potential relationship, without prior knowledge of any electrode kinetic parameter (i.e., the standard rate constant and the electron transfer coefficient). The mathematical procedure requires semi-integration of the current and previous knowledge of the formal potential of the studied redox couple. The theory predicts that very fast electrode processes, with an apparent electrochemical reversible behavior, are associated with anodic and cathodic current components the intensity of which is proportional to the standard rate constant. Thus, the proposed simple methodology provides a new perspective in analyzing voltammetric data and expands the accessible kinetic interval towards very fast electron transfer processes by means of simple voltammetry at macroscopic planar electrodes. The proposed methodology is experimentally illustrated with the electrode reaction of hexacyanoferrate(II) ion oxidation at platinum electrode.

Peculiarities of charge-discharge processes in Prussian white electrodes with different level of dehydration

Prussian White (PW) is a promising cathode material for sodium-ion batteries. PW exhibits advantages such as high specific capacity, ease of synthesis, and low cost. However, the presence of interstitial and coordinated water in PW materials significantly influences their electrochemical properties. In this work, a dehydration of the commercial PW powder and an impact of the preheating of the PW electrodes on their structural and electrochemical behavior have been examined using in situ/operando neutron and X-ray diffraction, along with complex TG-IR and FTIR techniques. The dehydration of the PW powder under the vacuum annealing conditions occurs mainly between 100 and 150 °C. At temperatures above 180 °C, a decomposition of the PW powder is detected. Preheating the electrode at 180 °C promotes the formation of a larger fraction of dehydrated rhombohedral phase, resulting in higher capacity compared to electrodes without preheating and preheated at 140 °C. Carbon content has been shown to be an important factor for stable electrode cycling. Capacity values of ∼100 mAh g–1 and 83 mAh g–1 at 5 C and 10 C cycling rates, respectively, are achieved when using 15 wt% content of carbon additive for the electrode preparation. Structural aspects of the degradation of PW electrodes during cycling are discussed.

Optimisation and study of a welding process for aluminium and galvanised steel based on resistance welding

In this study, taking six-series aluminium alloy and DC06 galvanised steel resistance spot welding as the object of study, the impacts of the electrode cap shape and process parameters on the joint welding performance were analysed, and the electrode cap was optimised. The optimised process parameters involved the use of spherical asymmetric electrodes and a pre-welding preheating step for zinc extrusion treatment, followed by a double pulse for welding. The optimal parameters resulted in an aluminium/steel spot welding head average pull shear failure load of 2858.7 N and aluminium/aluminium spot welding head failure force of 2436 N, reaching 117.3% of its original value. The minimum force value (2253.4 N) was greater than 92.5%, and the failure section was all from the aluminium side in parent material button failure, achieving good final results.

Nitrogen, phosphorus, and sulfur co-doped carbon nanotubes/melamine foam composite electrode for high-performance vanadium redox flow battery

The high cost and complex modification process of carbon felt electrodes limits its further popularization in vanadium redox flow batteries (VFBs). By introducing low-cost melamine foam, nitrogen, phosphorus, and sulfur co-doped carbon nanotubes/ melamine foam composite electrode (NPS-CNTs-CMF) is designed and fabricated via immersing melamine foam in a solution containing N, P, and S co-doped CNTs. The integration of modified CNTs significantly enhances the conductivity and hydrophilicity of the electrode. Moreover, the composite electrode also demonstrates outstanding electrocatalytic activity owing to the heteroatom doping that further inspired the electrocatalytic activity of CNTs. Density function theory calculations further uncover that introducing heteroatoms on CNTs not only promotes the adsorption of vanadium ions but also facilitates the electron transfer between vanadium ions and MF substrate. As a result, the battery loading with NPS-CNTs-CMF exhibits excellent battery performance, achieving energy efficiency of 80.12 % at 300 mA cm–2. Additionally, the long-term cycling stability is attained over 200 consecutive charge-discharge cycles at 300 mA cm−2. This study provides a novel melamine foam material with low cost and simple modification, and this new composite structure stimulates the development of high-performance electrodes in VFBs.

The direct electrochemical detection of Salmonella paratyphi A

A novel biosensor based on the direct electrochemistry of Salmonella paratyphi A immobilized on pretreated glassy carbon electrode (PGCE) was established. It was essential that the trans-membrane and trans-wall direct electron transfer of guanine (G) in DNA strand inside viable Salmonella paratyphi A was captured by microwave irradiation for melting double-stranded DNA（dsDNA） into single-stranded DNA (ssDNA). When the microwave irradiation condition reached 100 W for 9 s, the oxidation peak current reached maximal levels in pH 6.0 phosphate buffer solution (PBS). Meanwhile the typical surface controlled and irreversible electrode process of G was revealed by cyclic voltammetry (CV) with participation of 2 protons and 2 electrons respectively. In addition, A linear relationship for the oxidation current of G with the logarithm of Salmonella paratyphi A concentration was established with the range from 2.10 × 103 to 2.10 × 106 CFU ∙ mL−1. The rapid quantification of viable Salmonella paratyphi A was achieved based on the direct electrochemical biosensor.