Electrode System Research Articles

Heterostructured GCN Nanosheets/ZnO nanoflowers for enhanced TMO loading: From high-performance three electrode systems to printed flexible asymmetric supercapacitors

Transition metal oxides (TMOs) are widely used in the development of high-energy-density devices due to their multiple oxidation states and their frequent heterostructuring with carbon-based materials. However, the synthesis process often leads to severe nanoparticle agglomeration and weak synergistic effects with carbon-based templates, thereby limiting their application potential. In this study, we constructed graphitic carbon nitride (GCN) nanosheets/ZnO nanoflowers (NFs) structures with high TMOs loading by utilizing GCN nanosheets, which are rich in surface nitrogen content, as enriched templates for metal ions in conjunction with ultrasonic cavitation. Compared with GCN nanosheets/ZnO nanoparticles (NPs), the ZnO NFs exhibited vertical growth and a fluffy structure on a 2D material template, which resulted in high electronic conductivity, a large effective surface area, hierarchical pores, and strong synergistic interactions with GCNs, thus improving electrochemical performance. This structural enhancement enabled the GCN/ZnO NFs electrodes to achieve a high specific capacitance of 1524F g−1 at a current density of 1 A g−1 in a three-electrode supercapacitor system. Additionally, we formulated GCN/ZnO NFs into electronic inks and used them for the mass production of flexible supercapacitors with the aid of dispensing printing technology. These flexible supercapacitors retained 94% of their specific capacitance even under extreme conditions of 90° torsion. Our proposed strategy of modulating TMOs and 2D structures can create active electrode materials with higher loading capacities, thereby enabling comprehensive customization in material design and device preparation processes.

Electrochemical activation and characterization of carbon cloth

Here, carbon cloth (CC), which is a disposable, inexpensive, conductive substrate, was electrochemically activated for the formation of function al groups on the electrode surface. The electrochemical activation of commercial CC was achieved in various acidic solutions such as 0.1 M H2SO4, 0.1 M HCl and 0.1 M HNO3 to create functional groups on the surface of the gas diffusion layer by applying a constant 100 mA current (galvanostatic) for 10 s, 20 s, and 30 s, respectively. The electrochemical measurements were conducted using a 3-electrode system, including disposable carbon cloth as a working electrode, saturated Ag/AgCl as a reference electrode and Pt wire as a counter electrode. The modified CCs were tested via cyclic voltammetry using 5 mM Fe(CN)63−/Fe(CN)64− redox probe. Electrochemical experiment results showed that acid treatment of CC resulted in a significant increase in peak current compared to bare CC, indicating formation of functional groups on the electrode surface and improved electrical conductivity.

Diagnostics of porcelain insulators by partial discharges characteristics

RELEVANCE of the research is in the development of a non-destructive method for diagnosing porcelain insulators of high-voltage electrical equipment based on analysis of the characteristics of partial discharges (PDs). The problem of the final stage of breakdown of both the discharge gap and porcelain insulators recognizing is currently has not solved. THE PURPOSE. Recognition of PDs in solid insulation, study of PDs characteristics in a pre- breakdown situation, recognition of defective insulators based on PDs characteristics analysing. METHODS. The study of PDs characteristics for a defective and functional porcelain insulator were carried out. To study the characteristics of various types of PDs, including in the pre-breakdown situation, a system of surface-needle electrode system was used. RESULTS. The article describes compares the PDs characteristics obtained using standard R-400 device and a digital storage oscilloscope (DSO) using a telescopic antenna. A technique for recognizing the development of the pre-breakdown situation of the surface-needle discharge gap and the porcelain insulator was developed. The technique for recognizing a defective porcelain insulator from the amplitude-phase diagrams (APD) of PDs was developed. The method for assessing the breakdown voltage of porcelain insulators based on the characteristics of partial discharges was developed. CONCLUSION. At the moment of transition to the pre-breakdown stage were observed a sharp increase in the counter-movement of charges of opposite polarity. In the stage immediately before the breakdown, near zero values of the applied voltage of negative polarity, ordered PDs of the same polarity as the applied voltage were recorded in large numbers. These discharges led to an increase in leakage current and were interpreted as initial corona discharges. These discharges were recorded both by a telescopic antenna in a surface-needle system and in porcelain insulators.

Highly efficient electrosynthesis of hydrogen peroxide through reversible transformation between catechol and o-benzoquinone on polydopamine modified carbon black

Carbon-based materials are more promising catalysts for H2O2 electrochemical production. However, the common method for modifying carbon-based materials is surface functionalization with harsh and uncontrollable reaction conditions, hindering the precise regulation of the active sites. Herein, we proposed a carbon-based material modified by polydopamine (CB-PDA) that was easily prepared and used in air diffusion electrode system for H2O2 production. The rapid and reversible transformation between catechol and o-benzoquinone on PDA could improve the H2O2 selectivity from 75.5 % to 97.0 % during the electrocatalytic process. The detection of adsorbed *HOOH and *OOH in oxygen reduction reaction proved the preference of CB-PDA for the two-electron pathway. The H2O2 formation rate constant of CB-PDA increased significantly from 25.85 to 60.82 mM h−1. The highest cumulative H2O2 concentration could reach 10200 mg L−1 in 9 h. Long-term operation tests proved the good operational stability. Furthermore, this system was cost-effective without additional aeration energy consumption and could achieve rapid disinfection in 10 min, which would have great potential to be used in environmental remediation.

Temperature-dependent electrochemical performance of CuS as electrode material for supercapacitor application

In this work, we synthesize copper sulfide as electrode materials using hydrothermal technique at different temperatures. The electrochemical performance of copper sulfide electrode in 3-electrode systems using 2 M KOH electrolyte is thoroughly studied using electrochemical techniques such as CV, GCD and EIS. The sample synthesized at 160 °C demonstrates that it has a specific capacitance of 232.5F/g at a charge–discharge current density of 1 A/g, maintains cyclic stability of 72.57 % during 500 GCD cycles at 5 A/g, highlighting its potential for supercapacitors applications. The results demonstrate that temperature significantly alters the electrochemical properties of the CuS.

Nickel Hydroxysulfide Electrocatalyst Promotes Urea Oxidation for Energy‐Saving Hydrogen Production

AbstractThe occurrence of oxygen evolution reaction (OER) almost consumes most of the electric energy of hydrogen production by electrocatalytic water splitting. The energy required in the process of electrochemical hydrogen production can be reduced by choosing urea oxidation reaction (UOR) instead of OER. In this work, nickel hydroxysulfide is synthesized on nickel foam (NiSOH/NF) and its electrocatalytic performance was tested in UOR. Experimental results show that the vulcanization catalyst requires a low potential of 1.38 V (vs RHE) to achieve a current density of 100 mA cm−2 in an electrolyte containing 0.5 M urea, which is 270 mV lower than the conventional OER process. This innovative approach has yielded a substantial reduction in the cell voltage necessary for overall water splitting under two electrode system, thereby enhancing its efficiency and feasibility.

Signal Acquisition and Algorithm Design for Bioimpedance-Based Heart Rate Estimation from the Wrist

Background: Heart rate (HR) is a critical biomarker that provides insights into overall health, stress levels, and the autonomic nervous system. Pulse wave signals contain valuable information about the cardiovascular system and heart status. However, signal acquisition in wearables poses challenges, particularly when using electrical sensors, due to factors like the distance from the heart, body movement, and suboptimal electrode placement. Methods: Electrical bioimpedance (EBI) measurements using bipolar and tetrapolar electrode systems were employed for pulse wave signal acquisition from the wrist in both perpendicular and distal configurations. Signal preprocessing techniques, including baseline removal via Hankel matrix methods, normalization, cross-correlation, and peak detection, were applied to improve signal quality. This study describes the combination of sensor-level signal acquisition and processing for accurate wearable HR estimation. Results: The bipolar system was shown to produce larger ΔZ(t), while the tetrapolar system demonstrated higher sensitivity. Distal placement of the electrodes yielded greater ΔZ(t) (up to 0.231 Ω) when targeting both wrist arteries. Bandpass filtering resulted in a better signal-to-noise ratio (SNR), achieving 3.6 dB for the best bipolar setup and 4.8 dB for the tetrapolar setup, compared to 2.6 and 3.3 dB SNR, respectively, with the Savitzky–Golay filter. The custom HR estimation algorithm presented in this paper demonstrated improved accuracy over a reference method, achieving an average error of 1.8 beats per minute for the best bipolar setup, with a mean absolute percentage error (MAPE) of 8%. Conclusions: The analysis supports the feasibility of using bipolar electrode setups on the wrist and highlights the importance of electrode positioning relative to the arteries. The proposed signal processing method, featuring a preprocessing pipeline and HR estimation algorithm, provides a proof-of-concept demonstration for HR estimation from EBI signals acquired at the wrist.

Co‐W (Hydr)oxide with Ultralow Ru Promotes Water Dissociation Coupled H+ Abstraction in Alkaline HER

AbstractThe hydrogen evolution reaction in alkaline water electrolysis is facilitated through the electrodeposition of trimetallic catalyst on nickel foam using the chronoamperometry technique. Specifically, the trimetallic catalyst CoWRu@NF is deposited onto a nickel foam substrate. The catalytic performance of this trimetallic catalytic electrode for the Hydrogen Evolution Reaction (HER) is then assessed in a 1.0 M potassium hydroxide (KOH) solution. This specially designed trimetallic catalytic electrode system efficiently provides the more active sites through the Co component. Subsequently, it facilitates the reduction of protons (H+) to generate hydrogen gas using the Ru component. Tungsten acts as a co‐catalyst in the system for water dissociation promotor by removing hydroxide formed after water dissociation and preventing the deactivation of Ruthenium by certain reaction intermediates. The CoWRu@NF trimetallic catalyst demonstrates excellent activity, showcasing a low overpotential (−8 mV) to achieve a current density of (−10 mA/cm2. Additionally, it exhibits low Tafel slope values (101.2 mV dec−1), credited to the presence of cobalt and tungsten alongside Ruthenium in the catalytic system. This configuration is specifically designed to enhance the kinetics of the hydrogen‐evolving reaction.

Local Orientation Transitions to a Lying Helix State in Negative Dielectric Anisotropy Cholesteric Liquid Crystal

Orientation transitions in a cholesteric liquid crystal (CLC) layer with negative dielectric anisotropy, under the influence of a non-uniform spatially periodic electric field created using a planar system of interdigitated electrodes, were studied experimentally and numerically. In the interelectrode space, transitions are observed from a planar Grandjean texture, with the helix axis perpendicular to the layer plane, to states with a lying helix, when the helix axis is parallel to the layer plane and perpendicular to the electrode stripes. It was found that the relaxation time of the induced state in the Grandjean zones, corresponding to two or more half-turns of the helix, significantly exceeded the relaxation time for the first Grandjean zone with one half-turn. An analysis of experimentally observed and numerically simulated textures shows that slow relaxation to the initial state in the second Grandjean zone, as well as in higher-order zones, is associated with the formation of local topologically equivalent states. In these states, the helix has a reduced integer number of helix half-turns throughout the layer thickness or unwound into the planar alignment state.

Does the Formation of a Taylor Cone in a Pulsating Electrospray Directly Impact Mass Spectrometry Signals?

Electrospray ionization (ESI) remains the dominant technique in mass spectrometry (MS)-based analyses. Here, we investigated the relationship between a crucial aspect of ESI, the formation of the Taylor cone, and the MS ion current by utilizing a triple quadrupole (QqQ) mass spectrometer coupled with a streaming high-speed camera and a 3-ring electrode system. In one test, ion current over a 30-s plume gate (a ring electrode) opening was compared with the Taylor cone occurrence analyzed offline, with Spearman's correlation coefficients consistently near 0 despite parameter variations. In another test, real-time detection of Taylor cones was synchronized with QqQ-MS, selectively opening (de-energizing) the plume gate based on the Taylor cone status. This approach enabled matching the ion current with the Taylor cone occurrence. There was no apparent difference between the MS signals recorded in the presence and absence of a Taylor cone. Additionally, a Faraday plate was employed as a detector in offline experiments, revealing agreement between the frequency of liquid meniscus (Taylor cone) oscillation (∼1.92 kHz)-measured by high-speed imaging-and the frequency of spray current (∼1.93 kHz). We suggest that the lack of positive correlations in the MS experiments is due to intrinsic ion carryover during transit from the ion source to the detector and due to the insufficient data acquisition rate of the mass spectrometer, which erases short-term fluctuations of ion current.

Facile synthesis of MCo2O4(M= Ni, Cu, and Zn) materials for high-performing electrochemical capacitors with robust cyclic stability using redox additive electrolyte

Developing efficient electrochemical capacitors relies heavily on the quality of electrode materials and electrolytes used. This report presents the successful solvothermal synthesis of three cobaltites, NiCo2O4, CuCo2O4, and ZnCo2O4, and their electrochemical performance in a 2 M KOH electrolyte. Among the three cobaltites, NiCo2O4 showed the best electrochemical performance, delivering a specific capacity of 178 C/g when using FTO (fluorine-doped tin oxide) as the current collector. In addition, the performance of NiCo2O4 was tested in different aqueous electrolytes, including KOH, NaOH, NaCl, and Na2SO4, and the specific capacity was found to vary in the order of 2 M KOH > 2 M NaOH > 2 M NaCl > 2 M Na2SO4. The performance of NiCo2O4 was also assessed in various concentrations of KOH electrolyte (2 M KOH, 3 M KOH, and 4 M KOH), and the best performance was observed in 3 M KOH with a specific capacity of 928.3 C/g with Ni foam as the current collector. Finally, using redox additive electrolytes, the electrochemical performance of NiCo2O4 was evaluated in both 3-electrode and 2-electrode systems. No studies have been conducted on the electrochemical performance of NiCo2O4using KFCN redox additive in a 3 M KOH electrolyte. In the three-electrode system, NiCo2O4 showed a high specific capacity of 1005.5 C/g at 1 A/g, with 167 % capacity retention after 1000 charge-discharge cycles at a high current density of 30 A/g. The NiCo2O4//Activated Carbon asymmetric hybrid supercapacitors(AHSC) exhibited a maximum specific capacity of 115.6 C/g and a specific energy density of 85 Wh/kg at current density of 1 A/g. The AHSC also showed a capacitive retention of 120 % after 5000 charge-discharge cycles. The maximum power density was 13225 W/kg at a current density of 5 A/g while maintaining an energy density of 22 Wh/kg.

Chemical coupling engineered exceptional overall water splitting of autogenic NiS/FeS/NiFeOOH heterostructure

The commercial application of hydrogen production is heavily subjected to the expensive and complex fabrication of required bifunctional catalysts integrated with good oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) activity. Herein, a simple one-spot hydrothermal technique is advocated to simplify the synthesis of NiS/FeS/NiFeOOH heterostructure (denoted as NiFeS) and achieve exceptional bifunctional electrocatalyst for water splitting. Such NiFeS heterostructure reveals multi-synergistic heterointerfaces with chemical coupling to provide more accessible active sites, regulate electronic structure of the active center and enhance interfacial charge transfer, enabling a significant contribution in improving the catalysis. Therefore, the OER overpotential of NiFeS catalyst is only 249 mV to supply 100 mA cm−2 current density, and the overpotential for HER reaches to 153 mV at 10 mA cm−2. When constructed into a lab-made electrode system, it confirms a remarkable cell voltage of only 1.51 V at 10 mA cm−2 for water splitting, along with an exceptional durability up to 100 h at 100 mA cm−2. This study gives a novel insight into heterostructure engineering for the construction of bifunctional electrocatalysts.

Approach to Validate ISPM-15 Compliance for Commercial Treatment Certification of Dielectric Standard Heating of Bulk Solid Wood Packing Materials using Radio Frequency

Abstract To substantially reduce the risk of alien invasive species moving to new geographic areas, phytosanitary treatment of wood packaging materials (WPM) in compliance with the International Standard of Phytosanitary Measures No. 15 (ISPM-15) is required by trading partners. Approved treatments include conventional heating, methyl bromide and sulfuryl fluoride fumigation, and dielectric heating (DH). The DH standard was officially adopted in 2013 but has not been practiced commercially due primarily to insufficient operational validation at commercial scale. In 2022, we converted our 50-kW radio frequency (RF) unit with a 1,200-board foot capacity from an oscillator electromagnetic field power generator to a solid-state power supply, which allows for selective power input adjustments during treatment; we also switched from a five-plate to a three-plate winged electrode system to improve heating uniformity. Each loading cycle can treat sufficient material to build ∼94 standard Grocery Manufacturers Association pallets. Our research team characterized the dielectric heating pattern and options for monitoring wood temperatures over a wide-ranging test matrix of WPM that varied by wood species, dimension, moisture content, and loading configuration. We found that this upgraded RF system markedly reduced treatment times and improved heating uniformity, allowing us to develop methods that can be used to verify compliance with ISPM-15 for improved technology transfer to industry. We also discuss the operational cost of RF treatment and make general cost comparisons to conventional heat treatment for WPM.

Unveiling active sites in FeOOH nanorods@NiOOH nanosheets heterojunction for superior OER and HER electrocatalysis in water splitting

The development of cost-effective, highly active, and stable electrocatalysts for water splitting to produce green hydrogen is crucial for advancing clean and sustainable energy technologies. Herein, we present an innovative in-situ synthesis of FeOOH nanorods@NiOOH nanosheets on nickel foam (FeOOH@NiOOH/NF) at an unprecedentedly low temperature, resulting in a highly efficient electrocatalyst for overall water splitting. The optimized FeOOH@NiOOH/NF sample, evaluated through time-dependent studies, exhibits exceptional oxygen evolution reaction (OER) performance with a low overpotential of 261 mV at a current density of 20 mA cm−2, alongside outstanding hydrogen evolution reaction (HER) activity with an overpotential of 150 mV at a current density of 10 mA cm−2, demonstrating excellent stability in alkaline solution. The water-splitting device featuring FeOOH@NiOOH/NF-2 electrodes achieves a voltage of 1.59 V at a current density of 10 mA cm−2, rivalling the state-of-the-art RuO2/NF||PtC/NF electrode system. Density functional theory (DFT) calculations unveil the efficient functionality of the Fe sites within the FeOOH@NiOOH heterojunction as the active OER catalyst, while the Ni centres are identified as the active HER sites. The enhanced performance of OER and HER is attributed to the tailored electronic structure at the heterojunction, modified magnetic moments of active sites, and increased electron density in the dx2-y2 orbital of Fe. This work provides critical insights into the rational design of advanced electrocatalysts for efficient water splitting.

INVESTIGATION OF PLASMA VISCOSITY AND MAGNETIC FORCES IN COAXIAL PLASMA DISCHARGE DEVICE

This paper investigates the axial plasma current sheath, PCS viscosity force, and its correlation with other magnetic forces acting on it at three different radial positions (2.625, 3.625, and 4.125 cm) within the annular space between the coaxial electrodes system of plasma discharge device (12 kV-56 kA) with positive central electrode. The rate of change of PCS momentum was also investigated at these axial and radial positions. The discharge processes are carried out with an argon gas pressure of 0.8 Torr. Experimental results of azimuthal magnetic induction as a function of axial and radial positions and Navier Stokes equation were employed to compute exactly, the rate of change of PCS momentum, axial magnetic force, magnetic pressure gradient force, and viscosity force.

Poole-Frenkel conduction in CdS single-layered and CdS/SnS2 heterojunction electrode system

In this communication, the prevalence of Poole-Frenkel conduction mechanism in two distinct semiconductor systems, CdS single-layered and CdS/SnS2 heterojunction electrode systems, is reported. X-ray diffraction (XRD) exhibits the formation of CdS quantum dots (QDs). A High resolution transmission electron microscopy (HRTEM) shows a discrete particle distribution of SnS2, tends to assemble into nanosheets. Poole-Frenkel conduction arises due to the trap distribution of CdS dots, modified by SnS2 sheets. Furthermore, the formation of heterojunctions with SnS2 shows promising enhancement in charge transport, characterized by reduced trap density and improved conductivity compared pristine CdS. The findings provide valuable insights into the fundamental charge transport processes in CdS/SnS2 system and offer potential avenues for optimizing the performance of electronic devices.

Исследование новых биполярных систем для радиочастотной абляции

Radiofrequency ablation (RFA) is a minimally invasive way to treat cancer. The main problem of RFA is insufficient heating volume. The aim of the work is to create new electrode systems to improve heating characteristics by increasing the number of electrodes operating in bipolar mode. Studies were carried out on a four-channel installation ‘METATOM-3’. The number of dual electrodes varied from 1 to 8. The results of thermal fields obtained with such electrode systems are presented. Potato, whose structure changes when heated up to 60°C, was used as a simulator of biological tissue for the first time, which allows visualising the volumetric picture of the thermal field. To investigate the temperature distribution in the heating volume, a thermal imaging study of the tissue simulators was also carried out. It was found that the increase in the number of electrodes and transition to bipolar mode make it possible to eliminate the need for switching and increase the uniformity of the resulting heating, which is evident from the results of thermal imaging study.

Investigation of electrochemical performance of gadolinium trichloride in asymmetric supercapacitor applications

The commercial Gadolinium tri chloride (GdCl3) electrode material exhibits high specific capacitance of 207.52Fg−1 in three electrode system at 1A/g with potential window 1.0 V. The GdCl3//Activated carbon (AC) asymmetric supercapacitor device in two electrode system achieves 188.14Fg−1 specific capacitance at 1 A/g with high potential window 1.7V. It possess high energy density 75.51Wh/kg, power density 850W/kg. and electrochemical stability of 92% of its initial capacitance after 5000 cycles. These demonstrate GdCl3 as an useful material for electrochemical energy storage devices. Further, electron paramagnetic resonance study on GdCl3 reveals g-factor 1.98 and line width ΔH = 221.8mT.

Motion Artifacts in Dynamic EEG Recordings: Experimental Observations, Electrical Modelling, and Design Considerations

Despite the progress in the development of innovative EEG acquisition systems, their use in dynamic applications is still limited by motion artifacts compromising the interpretation of the collected signals. Therefore, extensive research on the genesis of motion artifacts in EEG recordings is still needed to optimize existing technologies, shedding light on possible solutions to overcome the current limitations. We identified three potential sources of motion artifacts occurring at three different levels of a traditional biopotential acquisition chain: the skin-electrode interface, the connecting cables between the detection and the acquisition systems, and the electrode-amplifier system. The identified sources of motion artifacts were modelled starting from experimental observations carried out on EEG signals. Consequently, we designed customized EEG electrode systems aiming at experimentally disentangling the possible causes of motion artifacts. Both analytical and experimental observations indicated two main residual sites responsible for motion artifacts: the connecting cables between the electrodes and the amplifier and the sudden changes in electrode-skin impedance due to electrode movements. We concluded that further advancements in EEG technology should focus on the transduction stage of the biopotentials amplification chain, such as the electrode technology and its interfacing with the acquisition system.

A bio-feedback-mimicking electrode combining real-time monitoring and drug delivery

Effective disease management based on real-time physiological changes presents a significant clinical challenge. A flexible electrode system integrating diagnosis and treatment can overcome the uncertainties associated with treatment progress during localized interventions. In this study, we develop a system featuring a biomimetic feedback regulation mechanism for drug delivery and real-time monitoring. To prevent drug leakage, the system incorporates a magnesium (Mg) valve in the outer layer, ensuring zero leakage when drug release is not required. The middle layer contains a drug-laden poly(3,4-ethylenedioxythiophene) (PEDOT) sponge (P-sponge), which supplies the water to partially or fully activate the Mg valve under electrical stimulation and initiate drug release. Once the valve is fully opened, the exposed and expanded P-sponge electrode establishes excellent contact with various tissues, facilitating the collection of electrophysiological signals. Encapsulation with polylactic acid film ensures the system's flexibility and bioresorbability, thereby minimizing potential side effects on surrounding tissues. Animal experiments demonstrate the system's capability to mimic feedback modulation mechanisms, enabling real-time monitoring and timely drug administration. This integrated diagnosis and treatment system offers an effective solution for the emergency management of acute diseases in clinical settings.