Long-term Stability Of Electrode Research Articles

Tackling Challenges of Long-Term Electrode Stability in Electrochemical Treatment of 1,4-Dioxane in Groundwater.

Electrochemical advanced oxidation is an appealing point-of-use groundwater treatment option for removing pollutants such as 1,4-dioxane, which is difficult to remove by using conventional separation-based techniques. This study addresses a critical challenge in employing electrochemical cells in practical groundwater treatment─electrode stability over long-term operation. This study aims to simulate realistic environmental scenarios by significantly extending the experimental time scale, testing a flow-through cell in addition to a batch reactor, and employing an electrolyte with a conductivity equivalent to that of groundwater. We first constructed a robust titanium suboxide nanotube mesh electrode that is utilized as both anode and cathode. We then implemented a pulsed electrolysis strategy in which reactive oxygen species are generated during the anodic cycle, and the electrode is regenerated during the cathodic cycle. Under optimized conditions, single-pass treatment through the cell (effective area: 2 cm2) achieved a remarkable 65-70% removal efficiency for 1,4-dioxane in the synthetic groundwater for over 100 h continuous operation at a low current density of 5 mA cm-2 and a water flux of 6 L m-2 h-1. The electrochemical cell and pulse treatment scheme developed in this study presents a critical advancement toward practical groundwater treatment technology.

Enhanced OER performance by varying Al-WO3 electrocatalyst thickness: Process optimization

Oxygen evolution reactions (OER) are highly significant and play a critical role in the advancement of fuel cells, electrolyzers, chemicals, and solar energy conversion devices. The challenge in the quest is attributed to the absence of an efficient electrocatalyst assembly that functions optimally. A simple method of electrodeposition of Al:WO3 on a fluorinated tin oxide (FTO) electrode was used to investigate the OER in this study. The electrodepositions were achieved by employing a three-electrode cell at various scan rates ranging from 10 to 100 mV/s. During this investigation, the influence of the scan rate on electrocatalyst loadings and the impact of electrocatalyst layer thickness on the OER were examined. The electrodepositions of Al:WO3@FTO were analyzed using a range of optical, chemical, and physical techniques such as SEM, XRD, FT-IR, Raman spectroscopy, EDX, EDS mapping, and electrochemical tests. The FTIR and Raman analysis confirmed the synthesis of AL:WO3 while the peaks detected at angles 38.7° and 43° by XRD with planes (111) and (200), served as a distinctive characteristic for identifying aluminum (Al). The peaks observed at angles of 27.8°, 30.7°, 33°, 50.45°, and 58° correspond to WO3 material. The characterization techniques also confirmed that the synthesized material is highly crystalline in nature. The OER potential using Al:WO3@FTO electrodes with different electrocatalyst thicknesses, ranging from 8 nm to 31 nm was investigated by studying various electrochemical techniques such as CV, LSV, CPE, Tafel slope, HP2P splitting, EIS, TOF, short and long-term electrode stability, and double layer capacitance. The linear regression coefficient (R2) was also calculated to measure the relationship between the electrocatalyst's thickness and each electrochemical test. The findings indicated that increasing the scan rates resulted in thinner and denser electrodepositions on the FTO substrate as the thinnest film was formed at 100 mV/s. An inverse relationship between electrocatalyst layer thickness and OER activity was observed. The electrode with the thinnest and most compact electrocatalyst layer, specifically ED Al:WO3@FTO08, exhibited the lowest onset potential of 1.48 V and a maximum current of 84 mA/cm2 at 1.76 V. It also demonstrated superior reaction kinetics, as evidenced by its lower Tafel slope value of 49 mV/dec, which is the lowest among all the electrodes that were prepared. In particular, the electrode with a thin and compact electrocatalyst layer worked better in OER operations than the other five electrodes that had higher amounts of Al:WO3.

Is "Water in Salt" Electrolytes the Ultimate Solution? Achieving High Stability of Organic Anodes in Diluted Electrolyte Solutions Via a Wise Anions Selection.

The introduction of the water-in-salt (WIS) electrolytes concept to prevent water splitting and widen the electrochemical stability window, has spurred extensive research efforts toward development of improved aqueous batteries. The successful implementation of these electrolyte solutions in many electrochemical systems shifts the focus from diluted to WIS electrolyte solutions. Considering the high costs and the tendency of these nearly saturated solutions to crystallize, this trend can be carefully re-evaluated. Herein we show that the stability of organic electrodes comprising the active material perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), is strongly influenced by the solvation character of the anions rather than the concentration of the electrolyte solution. Even though the charging process of PTCDA involves solely insertion of cations (i.e., principal counter-ions), surprisingly, the dominant factor influencing its electrochemical performance, including long-term electrode stability, is the type of the co-ions (i.e., electrolytic anions). Using systematic electrochemical analysis combined with theoretical simulations, we show that the selection of kosmotropic anions results in fast fading of the PTCDA anodes, while a selection of chaotropic anions leads to excellent stability, even at electrolytes concentrations as low as 0.2 M. These findings provide a new conceptual approach for designing advanced electrolyte solutions for aqueous batteries.

Unravelling pH Changes in Electrochemical Desalination with Capacitive Deionization.

Membrane capacitive deionization (MCDI) is a water desalination technology employing porous electrodes and ion-exchange membranes. The electrodes are cyclically charged to adsorb ions and discharged to desorb ions. During MCDI operation, a difference in pH between feed and effluent water is observed, changing over time, which can cause the precipitation of hardness ions and consequently affect the long-term stability of electrodes and membranes. These changes can be attributed to different phenomena, which can be divided into two distinct categories: Faradaic and non-Faradaic. In the present work, we show that during long-term operation, as the electrodes age over time, the magnitude and direction of pH changes shift. We studied these changes for two different feed water solutions: a NaCl solution and a tap water solution. Whereas we observe a pH decrease during the regeneration with a NaCl solution, we observe an increase during regeneration with tap water, potentially resulting in the precipitation of hardness ions. We compare our experimental findings with theory and conclude that with aged electrodes, non-Faradaic processes are the prominent cause of pH changes. Furthermore, we find that for desalination with tap water, the adsorption and desorption of HCO3–and CO32– ions affect the pH changes.

Subthreshold Electrical Stimulation for Controlling Protein-Mediated Impedance Increases in Platinum Cochlear Electrode.

This study evaluated subthreshold biphasic stimulation pulses as a strategy to stabilize electrode impedance via control of protein adsorption. Following implantation, cochlear electrodes undergo impedance fluctuations thought to be caused by protein adsorption and/or inflammatory responses. Impedance increases can impact device power consumption, safe charge injection limits, and long-term stability of electrodes. Protein-mediated changes in polarization impedance (Zp) were measured by voltage transient responses to biphasic current pulses and electrochemical impedance spectroscopy, with and without protein solutions. Four subthreshold stimulation regimes were studied to assess their effects on protein adsorption and impedance; (1) symmetric charge-balanced pulses delivered continuously, (2) at 10% duty cycle, (3) at 1% duty cycle, and (4) an asymmetric charge balanced pulse delivered continuously with a cathodic phase twice as long as the anodic phase. The Zp of electrodes incubated in protein solutions without stimulation for 2 h increased by between ∼28% and ∼55%. Subthreshold stimulation reduced the rate at which impedance increased following exposure to all protein solutions. Decreases in Zp were dependent on the type of protein solution and the stimulation regime. Subthreshold stimulation pulses were more effective when delivered continuously compared to 1% and 10% duty cycles. These results support the potential of subthreshold stimulation pulses to mitigate protein-mediated increase in impedance. This research highlights the potential of clinically translatable stimulation pulses to mitigate perilymph protein adsorption on cochlear electrodes, a key phenomenon precursor of the inflammatory response.

Green synthesis of CoWO4 powders using agar-agar from red seaweed (Rhodophyta): Structure, magnetic properties and battery-like behavior

This work reports a proteic sol-gel green method that uses agar-agar from red seaweed (Rhodophyta) for synthesizing cobalt tungstate (CoWO4) powders for battery-like electrodes. For comparison, CoWO4 is also prepared by a similar proteic chemical route that uses flavorless gelatin. The as-prepared powders were calcined at 800 °C for 2 h and further characterized by XRD (with Rietveld refinement), SEM/EDS, FTIR/Raman/UV–Vis–NIR spectroscopies, VSM, and various electrochemical techniques for assessing the battery-like behavior in alkaline media (3 M KOH). The results indicate that samples produced by gelatin show average particle size of 150 nm and crystallite size of 68 nm, against 284 nm (particle) and 84 nm (crystallite) for agar-agar processed materials. Magnetic assessment at 300 K showed a paramagnetic behavior for both samples. The analysis of these curves showed an effective magnetic moment per cobalt atom of 4.908 μB and 4.926 μB for samples prepared using gelatin and agar-agar, respectively. The performance of CoWO4 as battery-like electrodes is ascribed due to a surface faradaic redox reaction mechanism related to reversible valence state between Co2+ and Co3+. Discharging curves indicate no substantial difference of electrochemical performance, with maximum specific capacity of 77 C g−1 at a specific current of 1 A g−1. The long-term stability of electrodes is confirmed by a capacity retention of around 98% over 1000 charge-discharge cycles at 1 A g−1.

(Keynote) Electroreduction of CO2 on Pb and Bi Nanoneedles

The rise in atmospheric CO2 concentration since the beginning of the Industrial Age has raised concerns on its potential effect on global temperatures. While several factors such as natural climate changes, variations in solar activity, and volcanic eruptions may also contribute to observed variations in CO2 concentrations, it has been well established that anthropogenic emissions contribute to the annual emission of over 30 billion tonnes of CO2, only about half of which is recycled through natural pathways. CO2 conversion into value-added products is an avenue explored to mitigate environmental issues. Conversion methods appear promising, as they offer the potential to produce liquid and gaseous fuels for use either in the aeronautics industry, or as a chemical storage method for the intermittent energy produced by windmills and photovoltaic panels. Fuel synthesis may be achieved via either the production of a syngas mixture (H2 and CO) through the water gas shift reaction and subsequent conversion into hydrocarbon fuel through processes such as Fisher-Tropsch, or by direct electrochemical reduction of CO2. While all methods may result in similar conversion yields, depending on the catalyst used, direct electrochemical conversion of CO2 into value-added products is a low-temperature process, with the further advantage of requiring relatively simple equipment. Formic acid, or formate salts, are used in a variety of chemical processes such as electrowinning, leather tanning, and aircraft de-icing. Alternatively, formic acid and formate salts may be considered a hydrogen storage medium. Direct formic acid, and more recently, direct formate fuel cells, have been investigated in the literature as they demonstrate significant benefits over methanol fuel cells, including higher open circuit voltage and lower crossover. Among earth-abundant CO2 electrocatalysts, Sn, Pb and Bi are known to be highly selective for formate production, with faradic efficiency (FE) > 90%. However, several challenges need to be addressed for these materials to become viable alternatives for industrial applications based on an ERC process to become economically viable. In particular, issues related with large overpotential and low current densities need to be addressed, along with the long term stability of electrodes. In this study, we compared the activity and stability for CO2 electroreduction of high surface area metallic Bi and Pb nanoneedles (see Figure 1). In both cases, the materials films were prepared through a direct electrodeposition (potentiostatic method). Both types of films were extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and x-ray diffraction (XRD), while electrochemical activities were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potentiostatic measurements. Figure 1

Oriented Polyaniline Nanowire Arrays Grown on Dendrimer (PAMAM) Functionalized Multiwalled Carbon Nanotubes as Supercapacitor Electrode Materials

At present, PANI/MWNT composites have been paid more attention as promising electrode materials in supercapacitors. Yet some shortcomings still limit the widely application of PANI/MWNT electrolytes. In this work, in order to improve capacitance ability and long-term stability of electrode, a multi-amino dendrimer (PAMAM) had been covalently linked onto multi-walled carbon nanotubes (MWNT) as a bridge to facilitating covalent graft of polyaniline (PANI), affording P-MWNT/PANI electrode composites for supercapacitor. Surprisingly, ordered arrays of PANI nanowires on MWNT (setaria-like morphology) had been observed by scanning electron microscopy (SEM). Electrochemical properties of P-MWNT/PANI electrode had been characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge technique. The specific capacitance and long cycle life of P-MWNT-PANI electrode material were both much higher than MWNT/PANI. These interesting results indicate that multi-amino dendrimer, PAMAM, covalently linked on MWNT provides more reaction sites for in-situ polymerization of ordered PANI, which could efficiently shorten the ion diffusion length in electrolytes and lead to making fully use of conducting materials.

Material and Structural Design of Novel Binder Systems for High-Energy, High-Power Lithium-Ion Batteries

Developing high-performance battery systems requires the optimization of every battery component, from electrodes and electrolyte to binder systems. However, the conventional strategy to fabricate battery electrodes by casting a mixture of active materials, a nonconductive polymer binder, and a conductive additive onto a metal foil current collector usually leads to electronic or ionic bottlenecks and poor contacts due to the randomly distributed conductive phases. When high-capacity electrode materials are employed, the high stress generated during electrochemical reactions disrupts the mechanical integrity of traditional binder systems, resulting in decreased cycle life of batteries. Thus, it is critical to design novel binder systems that can provide robust, low-resistance, and continuous internal pathways to connect all regions of the electrode. In this Account, we review recent progress on material and structural design of novel binder systems. Nonconductive polymers with rich carboxylic groups have been adopted as binders to stabilize ultrahigh-capacity inorganic electrodes that experience large volume or structural change during charge/discharge, due to their strong binding capability to active particles. To enhance the energy density of batteries, different strategies have been adopted to design multifunctional binder systems based on conductive polymers because they can play dual functions of both polymeric binders and conductive additives. We first present that multifunctional binder systems have been designed by tailoring the molecular structures of conductive polymers. Different functional groups are introduced to the polymeric backbone to enable multiple functionalities, allowing separated optimization of the mechanical and swelling properties of the binders without detrimental effect on electronic property. We then describe the design of multifunctional binder systems via rationally controlling their nano- and molecular structures, developing the conductive polymer gel binders with 3D framework nanostructures. These gel binders provide multiple functions owing to their structure derived properties. The gel framework facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. The polymer coating formed on every particle acts as surface modification and prevents particle aggregation. The mechanically strong and ductile gel framework also sustains long-term stability of electrodes. In addition, the structures and properties of gel binders can be facilely tuned. We further introduce the development of multifunctional binders by hybridizing conductive polymers with other functional materials. Meanwhile mechanistic understanding on the roles that novel binders play in the electrochemical processes of batteries is also reviewed to reveal general design rules for future binder systems. We conclude with perspectives on their future development with novel multifunctionalities involved. Highly efficient binder systems with well-tailored molecular and nanostructures are critical to reach the entire volume of the battery and maximize energy use for high-energy and high-power lithium batteries. We hope this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of multifunctional binder materials.

Promoting Influence of Activated Carbon used in Carbon Paste Electrode on Platinum Nanoparticles Efficiency in Methanol Electrooxidation

Direct methanol fuel cell (DMFC) have the advantages of low emissions of carbon dioxide, high power density and high energy density, so they have a great potential to replace fossil fuels. It is well known that Pt with high activity is an ideal catalyst for methanol oxidation in an acidic medium. However, it is an expensive material, and cost of the DMFC containing Pt is prohibitively high and it becomes poisoned by COads which is formed during the methanol oxidation. In this work, for the first time, the preparation of activated carbon(YBC) doped carbon paste electrode (YBCPE) and carbon paste electrode (CPE) were carried out for comparison. The electrochemical properties of YBCPE and CPE were investigated by electrochemical impedance spectroscopy. The electrodes of Pt/YBCPE and Pt/CPE were prepared by electrodeposition of platinum on YBCPE and CPE, respectively, at a constant potential (−0.1V vs. Ag|AgCl(sat)) in 0.5M H2SO4 containing 3mM H2PtCl6. The behavior of electrodeposition of platinum on YBCPE and CPE was studied through the application of theoretical models, and the morphology of Pt/YBCPE and Pt/CPE were characterized by SEM. The electrochemical activities of these catalysts towards methanol electrooxidation were examined by cyclic voltammetry. The influence of YBC mass percentage in YBCPE on both the electrode activity and long-term stability of electrodes in methanol electrooxidation was studied. It was shown that the addition of activated carbon improved the electrocatalytic activity of Pt catalysts on corresponding YBCPE toward methanol electrooxidation.

Synergetic Effects of Inorganic Components in Solid Electrolyte Interphase on High Cycle Efficiency of Lithium Ion Batteries

The solid electrolyte interphase (SEI) is a passivation layer formed on an electrode surface that can enhance long-term electrode stability. The inorganic components formed in SEI layer, including lithium carbonate and lithium fluoride, play a critical role in terms of providing both mechanical and chemical protection as well as accommodating lithium ion transport. Although lithium carbonate and lithium fluoride have relatively low ionic conductivities, surprisingly, we find that a synthetic composite coating made of both components creates a defect-intensive interface, which significantly improves lithium transport. The synergetic effect of both inorganic components leads yields higher current efficiencies and cycling stability. We envision that the defect-intensive composite coating is a promising artificial SEI layer for the suppression of undesirable side reactions and improvement in the life of lithium ion batteries employing silicon negative electrodes.

Enhancing the photovoltaic performance and stability of QDSSCs using surface reinforced Pt nanostructures with controllable morphology and superior electrocatalysis via cost-effective chemical bath deposition.

To make quantum-dot sensitized solar cells (QDSSCs) competitive, photovoltaic parameters such as the power conversion efficiency (PCE) and fill factor (FF) must become comparable to those of other emerging solar cell technologies. In the present study, a novel strategy has been successfully developed for a highly efficient surface-modified platinum (Pt) counter electrode (CE) with high catalytic activity and long-term stability in a polysulfide redox electrolyte. The reinforcement of the Pt surface was performed using a thin passivating layer of CuS, NiS, or CoS by simple chemical bath deposition techniques. This method was a more efficient method for reducing the electron recombination in QDSSCs. The optimized Pt/CuS CE shows a very low charge transfer resistance of 37.01 Ω, which is an order of magnitude lower than those of bare Pt (86.32 Ω), Pt/NiS (53.83 Ω), and Pt/CoS (73.51 Ω) CEs. Therefore, the Pt/CuS CEs show much greater catalytic activity in the polysulfide redox electrolyte than Pt, Pt/NiS and Pt/CoS CEs. As a result, under one-sun illumination (AM 1.5G, 100 mW cm(-2)), the Pt/CuS CE exhibits a PCE of 4.32%, which is higher than the values of 1.77%, 2.95%, and 3.25% obtained with bare Pt, Pt/CoS, and Pt/NiS CEs, respectively. The performance of the Pt/CuS CE was enhanced by the improved current density, Cu vacancies with increased S composition, and surface morphology, which enable rapid electron transport and lower the electron recombination rate for the polysulfide electrolyte redox couple. Electrochemical impedance spectroscopy and Tafel polarization revealed that the hybrid CEs reduce interfacial recombination and exhibit better electrochemical and photovoltaic performance compared with a bare Pt CE. The Pt/CuS CE also shows superior stability in the polysulfide electrolyte in a working state for over 10 h, resulting in a long-term electrode stability than Pt CE.

Voltammetric determination of phytoinhibitor maleic hydrazide using PEDOT:PSS composite electrode

Maleic hydrazide (MH) was successfully detected using a novel electrochemical sensor based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-carboxymethyl cellulose-single-walled carbon nanotubes modified glassy carbon electrode (PEDOT:PSS-CMC-SWCNT/GCE). A commercially available aqueous PEDOT:PSS dispersion with good processability and conductivity was used as electrode modified substrate material, while a water-soluble and adhesive CMC was selected as both binder and dopant to improve the long-term electrode stability in water of the PEDOT:PSS composite film and obtain synergistically enhanced electrocatalytic ability for analytes. A commercially available SWCNT dispersion with good processability, enhanced electrocatalytic ability and large rough surface area was selected as enhancer to improve the sensing performance of PEDOT:PSS composite electrode. The properties of the prepared composite film and its electrode were characterized and employed for the electrochemical detection of MH. The electrochemical behaviors of MH, optimum experimental parameters, and the performance of sensing electrode were investigated. The fabricated PEDOT:PSS-CMC-SWCNT/GCE accelerated electron transfer, enhanced synergistically electrocatalytic ability toward MH oxidation and displayed excellent sensing performance such as wide linear range (0.8–51μM) and a low limit of detection (0.1μM) and good sensing stability.

Conducting poly(3,4-ethylenedioxythiophene):poly(styrene- sulfonate) film electrode with superior long-term electrode stability in water and synergistically enhanced electrocatalytic ability for application in electrochemical sensors

A novel poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) composite film with superior stability in water, adhesion and flexibility, which is very critical for maintaining the long-term stability in water of the PEDOT:PSS film electrode, was easily prepared by introducing a water-soluble, anionic, non-toxic and biocompatible biopolymer (sodium carboxymethyl cellulose, Na-CMC) into a commercially available aqueous dispersion of the conducting polymer (PEDOT:PSS dispersion). The high conducting PEDOT:PSS-CMC film exhibited good flexibility and long-term stability in water after being soaked in water for 35 days. The high performance film electrode with excellent adhesion, long-term electrode stability in water (retaining almost 99.4% of its original activity for 105 days), and electrochemical properties was prepared facilely by drop-coating, and displayed good synergistically enhanced electrocatalytic ability towards the anodic oxidation of harmful substances and nutritional ingredients in edible agro-products, which were employed for its application in electrochemical sensors. The simultaneous or individual detection of maleic hydrazide, salicylic acid, nitrite, sunset yellow, and tryptophan was successfully realized using PEDOT:PSS-CMC/GCE, and exhibited superior sensing stability. All satisfactory results indicated that the introduction of CMC into PEDOT:PSS could improve the flexibility, adhesion, long-term electrode stability in water and electrocatalytic ability, which would provide a promising platform for the application in electrochemical fields of the high performance film electrode, especially the application in electrochemical sensors.

Mechanical Simulation of Neural Electrode-Brain Tissue Interface under Various Micromotion Conditions

Micromotion is one of the most important factors that influence the long-term stability of neural electrodes. In order to improve the long-term stability of brain-implanted electrodes, this study uses finite element simulation for static and transient analyses. In particular, the effects of micromotion frequency and adhesion state on the mechanical state of the electrode-brain tissue interface are investigated based on the commercial electrode A1x16-3-100-413. The results demonstrate that micromotion frequency has a great effect on the maximum von Mises (VM) stress, revealing that higher frequencies are more harmful than lower frequencies in terms of the long-term stability of the electrode. When the frequency is 20 Hz, the stress reaches its maximum value, and then increases very slightly with frequency increasing. Results also show that the degree of physical coupling between the electrode and the brain tissue has a significant influence on the interfacial mechanical state. Enhancing the adhesion between the electrode and the brain tissue can effectively decrease the stress, strain, and delamination of the microelectrode tip with respect to the adjacent neural tissue, and thus improve the working life of implanted electrodes. The cyclic hysteresis energy is highly dependent on the adhesion of the electrode-tissue interface; the energy values are highest for a low electrode-tissue physical coupling. The results indicate that it is important to minimize the micromotion of the brain tissue caused by neural electrodes. A neural electrode with a biofouling-resistant coating should thus be developed to optimize the interface to enhance the adhesion between the brain tissue and electrodes.

Preparation, characterization and application of alkaline leached CuNiZn ternary coatings for long-term electrolysis in alkaline solution

The NiCuZn ternary coating was electrochemically deposited on a copper electrode. Then, it was etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). The surface composition of coating before and after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies were investigated by scanning electron microscopy (SEM). The long-term stability of electrode prepared for alkaline water electrolysis was investigated in 1 M KOH solution with the help of cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques. It was found that, the NiCuZn coating has a compact and porous structure with good physical stability. Alkaline leaching process further improved the activity of NiCuZn coating in comparison with binary NiCu deposit for the HER. The long-term operation at −100 mA cm −2 showed good electrochemical stability over 120 h.

Using room temperature ionic liquid to fabricate PEDOT/TiO 2 nanocomposite electrode-based electrochromic devices with enhanced long-term stability

In this work, poly(3,4-ethylenedioxythiophene)(PEDOT) was electrochemically incorporated with nano- and mesoporous TiO 2 films to form PEDOT/TiO 2 nanocomposite electrochromic electrodes. TiO 2 films were introduced to enhance the interfacial adhesion of the polymers to the substrates and thus increase the long-term stability of electrodes of electrochromic devices (ECDs). Room temperature ionic liquid (RTIL)- 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]BF 4) was employed to serve as electrolyte during the entire fabrication processes. With these efforts, the ECDs were found to retain up to 95% of their optical response and electroactivity after 10,000 deep, and double potential steps, exhibiting enhanced long-term stability.

The international campaign on intercomparison between electrodes for geoelectrical measurements

In many applications of electrical geophysics, the electrodes used to detect signal seem to be an important source of noise. To identify which electrodes were most stable for electric field measurements; an international campaign to evaluate electrodes for long-term monitoring of the telluric field was held at Garchy, France from April 1995 to April 1996. More than fifty different electrode pairs from researches around the world were tested in the campaign. Most of electrodes were metal-electrolyte designs, but with different construction details. The inter-comparison was carried out through laboratory and field experiments. The results of the experiment showed a surprising variation between the performances of different electrodes. Stability as determined in a brief laboratory experiment proved to be an excellent predictor of long-term field stability. Instabilities of differing qualitative character were observed during the year-long experiment. Linear drift may be caused by gradual changes in ground contact, leaking of electrolyte, or changes in chemical concentration of electrolyte within the electrodes. Sudden onset transient noise, which could be as large as 20 mV, is likely to be an electrochemical process such as reaction charge release and charge accumulation within the electrodes. Other physical causes of drift could be due to mechanical contact problems. Of metal electrodes, stainless steel is by far the best.The conclusions from the Garchy experiment are relevant to exploration geophysics: self-potential surveys are strongly affected by the long-term stability of electrodes and some electrodes may also have internal noise exceeding 1 mV per Hz in the frequency band around 1✓Hz, thus potentially affecting measurements of Induced Polarisation data.

Highly-dispersed copper microparticles on the active gold substrate as an amperometric sensor for glucose

A bimetallic electrode composed of copper microparticles dispersed onto a gold surface (Au/Cu) has been investigated as an amperometric sensor using glucose as a model compound. Such a sensing electrode has been prepared by electrochemical deposition of Cu 0 from 50 mM Cu 2+ and subsequent potential cycling in an alkaline medium. The morphology of the copper deposit has been examined by scanning electron microscopy. The effects of copper loading, scan rate, hydroxide concentration, and applied potential on the electrocatalytic oxidation of glucose have been also investigated. Long-term electrode stability, background current, sensitivity, and linear range of the Au/Cu electrode have been assessed for constant-potential amperometric detection (DC) at +0.550 and +0.350 V, and in pulsed-potential amperometric detection (PAD). When used as an amperometric sensor in the DC mode at an applied potential of +0.350 V, the bimetallic electrode yields a detection limit of 0.8 pmol glucose (S/N=3) with a linear dynamic range of four orders of magnitude. Comparable results have been obtained when the bimetallic sensing electrode was used in the DC mode at +0.550 V and in the PAD mode. Good mechanical stability under forced flow hydrodynamic conditions was also found upon changing the detection mode from DC to PAD and vice versa, making the multifunctional amperometric sensor very attractive for analytical applications in flowing streams.

Development of a carbon composite electrode made from polyethylene and graphite powder modified with copper(I) oxide

Solid carbon composite electrodes (CCEs) prepared by copper(I) oxide (Cu 2O) dispersed in polyethylene and graphite powder have been investigated for use as working electrode in amperometric flow-through detection in alkaline solutions. The effects of matrix composition, electrocatalyst loading, short- and long-term electrode stability, noise current, and sensitivity were assessed using d-mannitol as a model compound. Excellent sensitivity accompanied by a low residual current was observed with a 50% (w/w) Cu 2O loading level in the carbon paste matrix. An estimate value of the double layer capacitance, evaluated by cyclic voltametry in 0.48 M NaOH, was about 1360 μF/mm 2. Upon optimizing the sensing electrode in terms of composite electrode formulation, hydroxide ion concentration, and operating potential, the detection limit for d-mannitol in flow injection mode, using a wall-jet flow cell, was 5 μM for 50 μl injections. The bulk Cu 2O-CCEs exhibit good mechanical stability under forced flow hydrodynamic conditions, and overall offers the advantage of a very low background current. An additional inherent feature of these catalyst-modified electrodes is their renewal capability; the surface can rapidly be renewed by a simple polishing procedure making the amperometric sensor very attractive for routine quantitative measurements.