Electrode Response Research Articles

Tailoring the surface of a polymeric membrane with a thin-layer Nafion membrane: Construction of an anti-surfactant solid-contact ion-selective electrode

Surfactants are a type of amphiphilic chemicals that comprise both hydrophilic and hydrophobic regions, and the presence of surfactants would bring a detrimental effect on the potential responses of the solid-contact ion-selective electrodes induced by their extraction from the aqueous solution into the polymeric membrane phase. Herein, an anti-surfactant solid-contact Ca2+-selective electrode is proposed based on tailoring the surface of the polymeric membrane with the thin-layer Nafion membrane. The extraction of surfactants into the polymeric membrane can be eliminated through using the hydrophobic group of Nafion acting as “a polymer brush”, while the Ca2+ diffusion from the aqueous solution to the membrane phase is promoted by the hydrophilic group of Nafion based on the electrostatic interaction. The Nafion-functionalized solid-contact Ca2+-ISE shows an improved potential stability and an excellent potentiometric performance for detection of Ca2+ in the presence of cationic and anionic surfactants as compared to the traditional solid-contact Ca2+-ISE. Moreover, the anti-surfactant solid-contact ion-selective electrode is feasible for in situ measurement of Ca2+ at the interface between the seawater and the sediment. This work provides a general and facile strategy to eliminate the interferences of surfactants during the potentiometric measurements, and is favorable for in situ, on-site measurement with high accuracy and precision in the aquatic environment.

A micropore nanoband electrode array for enhanced electrochemical generation/analysis in flow systems.

Our previous work has established that micron-resolution photolithography can be employed to make microsquare nanoband edge electrode (MNEE) arrays. The MNEE configuration enables systematic control of the parameters (electrode number, cavity array spacing, and nanoelectrode dimensions and placement) that control geometry, conferring a consistent high-fidelity electrode response across the array (e.g., high signal, high signal-to-noise, low limits of detection and fast, steady-state, reproducible and quantitative response) and allowing the tuning of individual and combined electrode interactions. Building on this, in this paper we now produce and characterise a micropore nanoband electrode (MNE) array designed for flow-through detection, where an MNEE edge electrode configuration is used to form a nanotube electrode embedded in the wall of each micropore, formed as an array of pores of controlled size and placement through an insulating membrane of sub-micrometer thickness. The success of this approach is established by the close correspondence between experiment and simulation and the enhanced and quantitative detection of redox species flowing through the micropores over the very wide range of flow rates relevant, e.g., to applications in (bio)sensing and chromatography. Quantitative electrochemical reaction with low conversion, suitable for analysis, is demonstrated at high flow, whilst quantitative electrochemical reaction with high conversion, suitable for electrochemical product generation, is enabled at lower flow. The fundamental array response is analysed in terms of established flow theories, demonstrating the additive contributions of within-pore enhanced diffusional (nanoband edge) and advective (Levich-type) currents, the control of the degree of diffusional overlap between pores through pore spacing and flow rate, the control by design across length scales ranging from nanometer through micrometer to a centimetre array, and the ready determination of physicochemical parameters, enabling discussion of the potential of this breakthrough technology to address unmet needs in generation and analysis.

Exploring the synaptic response of reactive Mn electrodes based TiO2 resistive switches

Mn/TiO2/Mn devices, prepared by reactive sputtering and photolithography techniques, were characterized by analyzing their current–voltage (I-V) dependence, non-volatile memory properties, and artificial synapse behavior. The detailed study of its I-V characteristics allowed for highlighting the main conduction mechanisms involved in the electrical transport through the Mn-TiO2 junctions and determining an equivalent circuit model. These results show that the oxidation of metallic Mn electrodes and the application of electrical pulses produce a complex scenario associated with a highly inhomogeneous oxygen vacancy distribution. The resistance hysteresis switching loops were determined, as well as the synaptic-like weight depreciation and potentiation, revealing a linear dependence of the reset voltage as a function of the amplitude of the set voltage and a quasi-linear variation of the conductance with the number of applied pulses. Simulations based on spiking neural network architecture, considering different updates of the synaptic weights, were trained to learn handwriting patterns. Notably, those based on the linear learning rule of the Mn/TiO2/Mn devices outperformed others with increasing non-linear behavior, demonstrating both high recognition and noise tolerance factors, further highlighting the robustness of this approach.

A robust approach for designing a bismuth high entropy material (BiOXCO3) as a novel electrode material for supercapacitor applications

Modern scientific research development relies on high-entropy materials, which stand out for their intricate nature, positioning them as the nanomaterials of the future electrochemical energy storage device. In this work, we prepared a BiOX (X=Br, Cl, I) CO3 known as BiOXCO3 materials using a simple solvothermal approach. Further investigation was carried out on the electrochemical responses of electrodes based on BiOXCO3. BiOXCO3 (1) is the name given to the equal molar concentration of Br, Cl, I, and CO3. BiOXCO3 (2) was created when the concentration of Br was doubled, followed by BiOXCO3 (3) with Cl, BiOXCO3 (4) with I, and BiOXCO3 (5) with CO3. Among them, BiOXCO3 (5) has demonstrated a supreme specific capacitance value of 645 F g−1 at 1 A g−1. This preliminary work describes the tuning of the anion concentration in BiOXCO3 materials toward supercapacitor applications, paving the way for future investigations of bismuth-based high-entropy materials.

Electronic Response and Charge Inversion at Polarized Gold Electrode

AbstractWe have studied polarized Au(100) and Au(111) electrodes immersed in electrolyte solution by implementing finite‐field methods in density functional theory‐based molecular dynamics simulations. This allows us to directly compute the Helmholtz capacitance of electric double layer by including both electronic and ionic degrees of freedom, and the results turn out to be in excellent agreement with experiments. It is found that the electronic response of Au electrode makes a crucial contribution to the high Helmholtz capacitance and the instantaneous adsorption of Cl can lead to a charge inversion on the anodic polarized Au(100) surface. These findings point out ways to improve popular semi‐classical models for simulating electrified solid–liquid interfaces and to identify the nature of surface charges therein which are difficult to access in experiments.

Microwave-assisted vanadium interpolated cobalt-MOF cathode assembled 3 V high performing asymmetric supercapacitor with ionic liquid gel polymer electrolyte

To ameliorate energy storage and conversion, metal synergy, and structural stability, bimetal-assembled metal–organic frameworks (MOFs) are delved into. Augmented surface area, pseudo capacitance, and the ability to alter the MOF edifice of layered oxide have drawn interest in MOF-based oxide layered structures. Simple microwave and hydrothermal techniques use dimethyl formamide and water as solvents and annealing methods to generate the bimetallic organic framework’s Co3V2O8 and Co3VO4 cathode material. Those customized shapes boost redox sites and reduce ion electron distance. Due to cobalt’s faradaic process and vanadium’s highly layered attributes, supercapacitor electrode response is significant. Co3V2O8 has 1391F/g specific capacitance at 2 mV/s scan rate and 1309F/g at 4 mA/cm2 implemented current value. After 10,000 cycles, the cathode material depicts 89 % capacity retention and 98 % coulombic efficiency. Biowaste-derived activated carbon is combined with a Co3V2O8 cathode for asymmetric supercapacitor storage. That device works on 3 V windows with ionic liquid gel polymer electrolyte. With a maximum specific energy of 329.3 Wh/kg and specific power of 15250 W/kg, the achieved galvanometric capacitance is 263.5F/g and 220 mAh/g at the 9 mA/cm2 current and showed 88.5 % potential stability after 10,000 cycles. These findings corroborate its use as a supercapacitor cathode.

Ni/N/MPC Nanocomposites Synthesized via Microwave-Assisted Biomass Conversion for Efficient H2O2 Detection

In order to improve the sensitivity and stability of the material for the detection of hydrogen peroxide, Ni/N/MPC nanocomposites were synthesized by Ni-based biomass doped with nitrogen. Nickel atoms offer such advantages as good catalytic activity and low cost, while nitrogen doping facilitates the formation of stable hybrid structures and the formation of abundant functional groups on the surface of nanocomposites. The linear equation characterizing the electrode response from the Ni/N/MPC nanocomposites was derived from the relationship between the current signal I and H2O2 concentration, demonstrating a linear range of 0.05–240.15 mmol l−1, along with a detection limit of 0.84 μmol l−1 (S/N = 3). In contrast, the electrochemical signals from Ni/NGCE and Ni/N/GCE sensors were significantly lower than those obtained from the composite materials during cyclic voltammetry testing. In practical sample analysis, the recovery rate and RSD of H2O2 in tap water samples were 97.2%–98.6% and 5.5%–6.4%, respectively. The Ni/N/MPC/GCE sensing platform presents excellent stability and enhanced sensitivity.

Effect of current collector on the coupled electro-chemo-mechanical performance of graphite electrodes in LiBs.

The current collector, one of the main components in the manufacture of composite electrodes, is mainly used to enhance the mechanical stability and improve the performance and cycle performance of the electrodes. During the electrochemical reaction, the lithium diffusion can induce compressive stress and affect the mechanical performance, lifespan, and performance of batteries. Therefore, this study analyzed the influence of copper foil on the mechanical response and degradation performance of electrodes. In addition, a mathematical model was developed to analyze the effect of copper foil on the stress-strain behavior of the electrodes. The results indicated that the stress and modulus of the graphite electrodes have a non-linear increase with the lithiation process. Based on those findings, utilizing a thinner and more compliant current collector could effectively mitigate the in-plane strain and the stress within electrodes. Thus, developing a thinner and softer copper foil could simultaneously enhance the mechanical properties and specific density of composite electrodes for the next-generation LiBs.

Construction of Phenytoin Selective Electrodes and Its Application to Pharmaceutical Preparation

Phenytoin selective electrodes were constructed based on penytoin-phosphotungstate (Ph-PT) complex with different plasticizers; di-butyl phosphate (DBP), tri-butyl phosphate (TBP), di-butyl phthalate (DBPH),and o-nitro phenyl octyl ether (NPOE) phthalate. The electrodes based on DBPH, ONPOE plasticizers gave Narnistain slope which are, 56.4 and 55.3mV/decade with detection limit of 1.9x10-5 M , 1.8x10-5 and concentration range 10-1 to 10-4 M and pH range 3.0 – 8.0. The electrodes based on TBP and DBP showed non-Nernistain slopes, 40.2,40.5 mV/decade for both plasticizers. Interfering of some cations was investigated and shows no interfering with electrodes response. Potentiometric methods were used for measuring phenytion in pharmaceutical drugs (tablets) and the electrode based on DBPH was used for determination. The recovery obtained from measuring was in good agreements with that given in British Pharmacopeias.

Controlled single step synthesis, structural and electrode response of honeycomb layered Li3Co2SbO6

We report, for the first time, a single step synthesis process of Li3Co2SbO6 in air medium using the solid state reaction route. The structural analysis confirmed single phase layered crystal structure comprising 2D diffusion path along a-axis and b-axis. The Rietveld refinement of Li3Co2SbO6 yielded monoclinic crystal structure with C2/m space group having cell parameters, a = 5.216 A°, b = 8.989 A° and c = 5.171 A° with Li/Co mixed occupancy. The TEM analysis corroborated the layered structure which is consistent with x-ray analysis. Raman and FTIR analysis confirmed the presence of -CoO6 and -SbO6 octahedra in Li3Co2SbO6 with edge shared arrangement to form a layered stack comprising tunnel type pathway for Li+ ion transport. The estimated electrical conductivity of Li3Co2SbO6 is found to be ∼6.9 × 10−8 Scm−1 with a band gap ∼ 3.5 eV that suggests poor electronic transport for storage cells. This was observed in the electrochemical response of the Li || LiPF6(EC/EMC) || Li3Co2SbO6 cell. The 1st discharge capacity of Li3Co2SbO6 has been found to be a meagre 45 mAhg−1. Despite lower reversible capacity due to poor electrical transport, stable coulombic efficency observed up to 100 cycles suggest the feasibility of improvements in the electrical and charge transport properties.

Influences of marine biofouling on the potential responses of polymeric membrane ion-selective electrodes

Using polymeric membrane ion-selective electrodes (ISEs) for reliable long-term marine environmental observations is still a challenge due to the formation of biofilms on electrode surfaces. Unfortunately, the contributions of the specific biofilm components to sensor failure have not been studied. Herein, the influences of the specific biofilm components on the performance of the neutral carrier-based polymeric membrane ISEs are systematically investigated in terms of sensitivity, selectivity, and stability. More importantly, the spatial distributions of these foulants in the fouled sensing membrane phase are studied by confocal laser scanning microscopy for the first time to give insight into the fouling mechanisms. Three typical biochemicals (i.e., proteins, polysaccharides, microbial lipids) in biofilms are selected as the representative foulants. The poly (vinyl chloride)-based CO32--ISEs and K+-ISEs/Ca2+-ISEs have been selected as the model sensors for detection of anions and cations, respectively. Experiments show that depending on the type of the biofoulants, the adsorption of the foulants on the polymeric membrane surface and/or their extraction into the organic membrane phase could occur and induce a change in the potential responses. This study provides a deep insight into the influences of the specific biofilm components on the polymeric membrane ISEs, which is of importance for development of the polymeric membrane marine sensors with high antifouling capabilities for long-term marine monitoring.

Electrolytes in conducting nanopores: Revisiting constant charge and constant potential simulations.

Simulating electrolyte-electrode systems poses challenges due to the need to account for the electrode's response to ion movements in order to maintain a constant electrode potential, which slows down the simulations. To circumvent this, computationally more efficient constant charge (CC) simulations are sometimes employed. However, the accuracy of CC simulations in capturing the behavior of electrolyte-electrode systems remains unclear, especially for microporous electrodes. Herein, we consider electrolyte-filled slit nanopores and systematically analyze the in-pore ion structure and diffusivity using CC and constant potential simulations. Our results indicate that CC simulations provide comparable pore occupancies at high bulk ion densities and for highly charged pores, but they fail to accurately describe the ion structure and dynamics, particularly in quasi-2D (single-layer) pores and at low ion densities. We attribute these results to the superionic state emerging in conducting nanoconfinement and its interplay with excluded volume interactions.

Enhancing Heavy Metal Detection through Electrochemical Polishing of Carbon Electrodes.

Our research addresses the pressing need for environmental sensors capable of large-scale, on-site detection of a wide array of heavy metals with highly accurate sensor metrics. We present a novel approach using electrochemically polished (ECP) carbon screen-printed electrodes (cSPEs) for high-sensitivity detection of cadmium and lead. By applying a range of techniques, including scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, we investigated the impact of the electrochemical potential scan range, scan rate, and the number of cycles on electrode response and its ability to detect cadmium and lead. Our findings reveal a 41 ± 1.2% increase in voltammogram currents and a 51 ± 1.6% decrease in potential separations (n = 3), indicating a significantly improved active electrode area and kinetics. The impedance model elucidates the microstructural and electrochemical property changes in the ECP-treated electrodes, showing an 88 ± 2% (n = 3) decrease in the charge transfer resistance, leading to enhanced electrode electrical conductivity. A bismuth-reduced graphene oxide nanocomposite-modified, ECP-treated electrode demonstrated a higher cadmium and lead sensitivity of up to 5 ± 0.1 μAppb-1cm-2 and 2.7 ± 0.1 μAppb-1cm-2 (n = 3), respectively, resulting in sub-ppb limits of detection in spiked deionized water samples. Our study underscores the potential of optimally ECP-activated electrodes as a foundation for designing ultrasensitive heavy metal sensors for a wide range of real-world heavy metal-contaminated waters.

Hybrid TiO2–RGO nanocomposite as high specific capacitance electrode for supercapacitor

This study describes the fabrication of composite electrodes comprising TiO2 and reduced graphene oxide layers using a moderate-temperature hydrothermal method. The morphology, crystalline structure, chemical composition, and optical features of the prepared composites were analyzed by FE-SEM, x-ray diffraction, FTIR, and UV–visible spectroscopy. The cyclic voltammetry (CV) and Nyquist plots were used to assess the electrochemical and impedance responses of the composite electrodes, respectively. The analysis revealed that the incorporation of RGO reduced the TiO2 bandgap to 3.87 eV 3.02 eV and improved the specific capacitance, enhancing the TiO2-RGO electrode’s supercapacitive performance. CV studies highlight that the TiO2-RGO composite has a high specific capacitance of 152 F g−1 at a substantially faster scan rate of 25 mV s−1 in a 1.0 M-KOH dilute electrolyte. These findings confirmed the applicability of the fabricated electrodes as prospective supercapacitor electrodes.

Electrochemical detection of indigo carmine in candies using Y2O3 nanoparticles infused graphite electrode

This article presents the use of Yttrium Oxide (Y2O3) nanoparticles to modify the graphite paste electrode (GPE) for the sensitive and selective electrochemical determination of Indigo Carmine (ICN), one of the well-known synthetic food colorants. These nanoparticles were formed via a simple sol and gel method and characterized by a few non-destructive analytical methods like X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDX) techniques. The electrode response was studied via Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) methods for the variation of some fundamental parameters such as buffer, pH, scan rates, and concentrations. The efficiency of the developed Yttrium Oxide (Y2O3) nanoparticles modified Graphite Paste Electrode (Y2O3@GPE) sensor was assessed via repeatability, reproducibility and long-term stability analysis. Various similar interferants were added with ICN molecules for accomplishing the selectivity study while a widely linear operating range with a Limit of Detection (LOD) and a Limit of Quantitation (LOQ) of 0.11 µM and 0.35 µM, respectively were found. The performance of the electrode was justified in the real samples through its application for the detection of ICN in different candies where a satisfactory recovery rate of 96.25 %-117.5 % was achieved.

Disposable Carbon Electrochemical Sensor Modified with Gold Nanoparticles for Creatinine Detection

The social and economic impact of Chronic Kidney Disease on global health systems is devastating. It is estimated that annual spending on the treatment of Chronic Kidney Patients is in the order of 2 to 3% of annual health budgets. (1) In 2015, considering the United States, medical expenses for individuals with chronic kidney diseases were more than 64 billion dollars (1). Indeed, the early diagnosis of chronic kidney diseases is very important for the implementation of preventive measures that delay or even interrupt the progression to more advanced stages of the disease. In this context, this work aims to develop a disposable electrochemical sensor aimed at detecting creatinine for diagnosing kidney diseases. The flexible disposable lab made carbon sensor has been modified with gold nanoparticles. Morphological and electrochemical characterizations were carried out to better understand the proposed device. From cyclic voltammetry measurements, the proposed sensor showed reduction and oxidation peaks related to gold oxides formed on its surface. When adding creatinine there is a decrease in the electrochemical signal due to the adsorption of the target analyte. Therefore, it was inferred that it was possible to detect creatinine present in the solution from the reduction in the analytical response of the gold-modified electrode. Using the square wave voltammetry technique, in accordance with what was previously presented, when CNN was added to the solution, the Au-CNN interaction caused a reduction in the analytical response, therefore, with the increase in CNN concentration, this reduction increased linearly in the range of 0.5 to 10 µmol L-1 with a limit of detection and quantification, 0.15 and 0.45 µmol L-1, respectively, were calculated. Furthermore, it presented a sensitivity of 0.97 µA mol-1 L with a linear equation of Ipeak (µA) = 0.97 x C(CNN) + 0.23. Furthermore, the proposed sensor was successfully applied to determine creatinine in human serum samples and the recovery results were close to 100%. Therefore, the device modified with gold nanoparticles is an interesting alternative for creatinine detection.References(1) Luyckx V. A. et al. The global burden of kidney disease and the sustainable development goals, Bulletin of the World Health Organization Published online: 20 April 2018.

Passivation of Lead-Acid Batteries Lead Negative Electrodes by PbSO4 Crystals: Analysis from Modeling Cyclic Voltammetry Responses

Lead-acid batteries (LABs) play a pivotal role in the energy storage sector with applications spanning from starting-ignition-lightning batteries to grid energy storage. Passivation of lead negative electrodes by PbSO4 crystals is a one fundamental mechanism limiting the performance of LAB. In this regard, we developed an electrochemical mathematical model that simulates the nucleation and growth dynamics of PbSO4 crystals on a flat lead electrode, responsible for its passivation. The model considers the electrochemical dissolution of Pb2+ from lead electrode and the ternary transport of lead, bisulfate, and hydrogen ions in H2SO4 electrolyte. We have validated the model with a rich dataset of cyclic voltammetry (CV) responses collected at several scan rates and several concentrations of H2SO4. The model shows remarkable qualitative and quantitative agreement with the experimental data including the onset potential, center, height, and width of the CV peaks, discharge capacity, and particle size. The model is used to give insights on how different physical and operational parameters can influence the electrochemical response of lead negative electrodes. Keywords: lead-acid battery, nucleation and growth, passivation, cyclic voltammetry

Monitoring the Corrosion Resistance of Cold-Spray Coatings with Membrane-Based Sensors

Ensuring the management of gas transportation infrastructure requires the monitoring of internal corrosion within pipelines. The utilization of membrane-based electrochemical sensors is a promising advancement in corrosion risk monitoring. These sensors demonstrate an ability to operate within humidified gas environments, previously inaccessible to conventional electrochemical monitoring methods. Simultaneously, ongoing research is delving into novel sacrificial coatings and application methods to prolong the lifespan of existing pipeline structures and minimize associated repair costs. In this context, we broaden the application of membrane-based electrochemical sensors to investigate the response of electrodes equipped with cold-spray coatings. This examination encompasses a range of fluids exhibiting varying levels of corrosivity pertinent to natural gas pipelines. Multiple sensors with 316 stainless steel working electrodes were coated with cold spray sacrificial coating then exposed to humidified gases with differing relative humidities (RH) (5 %, 50 %, and 95 %) and condensed phases with differing salt content (deionized water and 0.1 mol kg-1 NaCl solution). Three electrochemical techniques (potentiometry, impedance spectroscopy and potentiodynamic scans) were used to monitor the corrosive environment and probe the extent of coating coverage. For the conditions studied, impedance values were extremely sensitive to changes in water content through changes in the membrane resistance (from ~1 kΩ in deionized water to ~5 MΩ with 5 % RH). Polarization resistances (Rp) consistently decreased with increasing corrosivity (~3 kΩ in deionized water to 15 GΩ with 5 % RH). Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to identify the extent to which corrosion products permeated the membrane after major corrosion events.

Deciphering the Role of p-Type ZnCo2O4 Semiconductor Nanoflakes for Selective Enhancement of Voltammetric Responses Toward Redox Species System: Interfacial Electron-Transfer Kinetics and Adsorption Capacity

In this study, we describe experimental efforts to decipher the role of ZnCo2O4 nanoflakes (ZCO-NFs) for selective enhancement of voltammetric responses of screen-printed electrode (SPE) toward redox species system. The ZCO-NFs sample was characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and UV–vis spectroscopy. The electrochemical characterization of bare SPE and modified SPE electrodes was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Mott−Schottky analysis. A series of redox systems including paracetamol (PA), dopamine (DA), chloramphenicol (CAP), furazolidone (FZD), p-nitrophenol (p-NP), carbaryl (CBR), ofloxacin (OXF), and erythromycin (ERY) were selected to investigate for (i) reversible redox process, (ii) irreversible electrochemical oxidation process, and (iii) irreversible electrochemical reduction process on both bare-SPE and ZCO-NFs/SPE electrodes. The obtained results showed that ZCO-NFs possess the selective enhancement of electrochemical response for redox systems with an increase of 24%–90% for PAR, DA, FZD, CAP, and CBR and a decrease of 13%–49% for p-NP, ERY, and OFX. The different electrochemical response of redox species at nanostructured semiconductor electrodes is attributed to the contribution of both the adsorption capacity of redox species and the interfacial electron transfer process between electrode and redox species. An insight into the interfacial electron transfer kinetics and its contribution to the enhancement of electrochemical response on p-type semiconductor electrode is helpful in designing high-performance sensing platforms based on spinel oxide nanostructures.

Multiphysics Modeling of the Electrochemical Response of Screen-Printed Electrodes for Sensing Applications

Multiphysics Modeling of the Electrochemical Response of Screen-Printed Electrodes for Sensing Applications