Benign Electrolytes Research Articles

Long-Life Zn Anode Enabled with Complexing Ability of a Benign Electrolyte Additive.

The development of aqueous zinc ion batteries (AZIBs) is hindered by several problems, including Zn dendrite/corrosion, side reactions, and hydrogen evolution reaction (HER). Herein, trisodium citrate (NaCit) additive is introduced into the ZnSO4 electrolyte to guide the preferred Zn(002) crystal plane growth, while the Cit- is preferentially adsorbed on the active sites to suppress the HER and Zn corrosion, thus achieving uniform Zn deposition without dendrites. The stable cycle life can reach 2000 h at 0.25 mA cm-2/0.05 mAh cm-2. The density functional theory simulations further indicate that the parallely placed Cit- has the lowest adsorption energy (-6.617 eV); it can form a weak interaction with Zn metal to promote the growth of (002) crystal planes. Furthermore, the assembled Zn//polyaniline full cell and pouch cell both exhibit good rate performance and long cycling stability. The complexation and dissolubilization effects of the NaCit additive provide a means for designing high-performance AZIBs.

Hydrodynamic voltammetry of Fe2+/3+ in aqueous deep eutectic solvents towards redox flow batteries

Deep eutectic solvents (DESs) have recently attracted much attention as potential green electrolyte solvents for redox flow batteries. DESs are considered not only as environmentally sustainable but also economically attractive electrolytes because they can be resourced from biological feedstock (alcohols, urea, choline) and are earth-abundant and of low toxicity. Despite these advantages, DESs still have limitations in important aspects such as reactant and ion transport, which is inhibited due to hydrogen-bonding-induced viscosity. Thus, improving the transport properties of redox species in DESs is essential. In addition, we explore the quantitative addition of water to ethaline (a 1:2 choline chloride: ethylene glycol mixture) in order to understand its influence on the kinetics and mass transport properties of DESs. In this work, we show that DESs can be made more fluid and less dense, while avoiding most of the electrochemical instabilities of water. Herein, we investigate the effects of gradually increasing amounts of water to the redox system of Fe2+/3+in ethaline. Our study shows that systematic addition of water leads to a three-fold increase in ionic conductivity and decrease in viscosity that enhances the mass transport and kinetics of DES-based electrolytes while still maintaining an electrochemical window of approximately 1.90 V. The use of environmentally benign electrolyte components together with the observed increase in conductivity will result in a more efficient redox flow battery (RFB) that operates at higher power density without relying on harmful solvents and fossil fuel-based processes.

(Digital Presentation) HF-Free, Pulse-Reverse Electrochemical Machining of Tantalum

Electrochemical machining (ECM) is a manufacturing technology wherein metal is precisely removed by electrochemical oxidation and dissolution/dispersal into an electrolyte solution. ECM is especially well suited for “difficult to cut” materials (high strength/toughness, work-hardening, etc.) such as high strength steel, chrome-copper alloy (C18200), nickel alloy (IN718), cobalt-chrome alloy (Stellite 25) and tantalum-tungsten alloy (Ta10W) since the material removal process involves no mechanical interaction between the tool and the part. In ECM, an electrochemical cell is established wherein the workpiece is the anode and the tool is the cathode; by relative movement of the shaped tool into the workpiece while applying a suitable electrical voltage, the mirror image of the tool is “copied” into the workpiece. Production of parts with complicated and intricate geometries can thus be achieved in these challenging materials by design of a suitably-shaped tool made from a much more easily-machinable material. Compared to mechanical or thermal machining processes, where metal is removed by cutting or electric discharge/laser machining, respectively, ECM does not suffer from tool wear or result in a thermally damaged surface layer on the workpiece. Additionally, the use of pulse and/or pulse-reverse electrical waveforms can enable successful ECM of even highly passive materials using benign, HF-free electrolytes.Advanced materials such as refractories (e.g., W, Mo, Ta, and their alloys) provide highly desirable characteristics such as high strength, corrosion resistance, and survivability in extreme environments (high temperature, high chemical reactivity, plasma exposure, etc.). As motivation to adopt these materials has increased, conventional fabrication methods have proven progressively less able to successfully machine workpieces of the myriad needed geometries. ECM is a natural non-conventional fabrication method for these materials and workpieces, for the reasons described above. In this talk, we will present results from a proof-of-concept demonstration of pulse-reverse ECM of linear grooves in flat Ta and Ta10W alloy coupons using benign electrolytes, illustrating the potential for cost-effective, safe, environmentally-friendly fabrication using these exotic materials.

Long‐Life Zn Anode Enabled by Low Volume Concentration of a Benign Electrolyte Additive

AbstractInexpensive and energy‐dense Zn metal anodes is key to the promise of aqueous Zn‐ion batteries, which are heralded as an exciting battery chemistry for renewable and stationary storage. Yet, Zn deposition instability under demanding cycling conditions leads to rapid dendritic cell failure, and the hydrogen evolution reaction aggravates the issue. Electrolyte additives are a scalable solution to address the problem, but a high volume fraction is typically required for a noticeable effect. Here, a benign alcohol molecule propylene glycol is presented as an electrolyte additive that enables remarkably stable Zn anode cycling of over 1000 h at a practical 2 mA–2 mA h cm−2 at a low volume concentration when the reference cell shorts only after 30 h. The dramatic performance improvement at the low additive concentration is attributed to the effective morphology regulation and inhibition of hydrogen evolution, as revealed by spectroscopic and microscopic investigations. Ab initio molecular dynamics simulations reveal unprecedented atomistic insights behind the concentration‐dependent effectivity of propylene glycol as an electrolyte additive. Excellent full cell cycling with two different positive host materials, even with high loading, highlights the potential for practical development.

Supercapacitance in graphene oxide materials modified with tetrapyrrole dyes: a mechanistic study.

The global increase in mobile technology usage has created a need for better energy storage systems. With standard batteries reaching their technological limits, alternate energy storage methods are gaining momentum. In this study, we demonstrate a cheap and efficient way of building from scratch high-performance supercapacitors based on graphene oxide (GO) functionalized with tetrapyrrole derivatives: porphyrins and phthalocyanines. We present supercapacitors with capacitances about 30 times larger than those of the pristine graphene oxide-based counterparts. Experimental characterisation methods including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-VIS), electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations revealed correlations between the structural, magnetic, electronic and thermodynamic properties of these materials and their performance as supercapacitors. Electrochemical studies indicate the complex and versatile nature of capacitive effects associated with thin layers of supramolecular composites of graphene oxide. The electrical double layer (EDL) capacitance, cation intercalation and faradaic processes are coupled. Moreover, differences in the electronic interactions between GO and tetrapyrrolic modifiers have a profound effect on the observed capacitance. At the same time, these interactions are sufficiently weak to induce only subtle spectral changes, as well as a small increase of the interlayer distance as determined by XRD measurements. The present work offers a viable strategy for manufacturing high-performance supercapacitive materials that are superior to the state of the art nanocarbon-based supercapacitors using benign electrolytes in terms of capacitance per mass unit and have the potential for application in future green energy storage technologies. Our study provides insight into the multifarious origins of supercapacitance beyond the well-known EDL mechanism.

Electrode Materials for Enhancing the Performance of a Zinc Iodide Flow Battery at High Current Density

The zinc-iodide flow battery (ZIFB) has a high energy density and uses a benign electrolyte material [1]. However, the energy density and cyclability the ZIFB is hindered by zinc dendrite growth and electrode polarization in this battery [2]. In our previous work a new flow field design was used to mitigate dendrite formation and enhance the performance of the ZIFB [3]. Despite the enhancement achieved, capacity fade and limited cyclability at current densities greater than 20 mA cm- 2 remain a challenge for ZIFBs. In this study, the use of a high electrical conductivity material for the negative (zinc) electrode, combined with an electrocatalyst on the positive (iodide) electrode was investigated, in order to improve the cyclability and energy density of the ZIFB at high current densities.The use of a high electrical conductivity electrode has been shown to enable rapid transfer of surface charge, and maintain a uniform interfacial electric field [4]. A uniform interfacial electric field can reduce surface charge accumulation and enable a more uniform zinc deposition [5]. This leads to uniform zinc deposition and high rechargeability of the zinc electrode. In this study a copper foil was used as a high conductivity electrode material at the negative (zinc) side of the ZIFB. Scanning electron microscopy (SEM) images of the zinc deposit show that epitaxially layered deposition was obtained on the electrode surface. For all the experiments, charge/discharge of a Zn-I battery were carried out using a 3.0 M ZnI2 electrolyte on both sides of the battery, the charge and discharge current density was 40 mA cm-2, and charging was carried out to 60% state of charge. A Nafion 117 membrane was used to separate the electrolyte compartments.Nitrogen doped carbon obtained by carbonizing polyaniline (PANI) is a promising electrocatalyst material for the next generation energy storage technologies [6]. A carbonized PANI-graphite felt composite was used as the electrode material on the positive (iodide) side of the ZIFB. PANI was uniformly coated on graphite felt using brush, followed by heating to 850 °C for 2 hours under the N2 atmosphere. The use of the carbonized PANI modified graphite felt electrode material in the positive side of the ZIFB (with a graphite felt negative electrode), led to an enhancement of the energy efficiency of around 4% (from 67 % to 71%) at a current density of 40 mA cm-2. The carbonized-PANI modified electrode was characterized using X-ray diffraction, Raman spectroscopy, nitrogen adsorption, and SEM. SEM results indicated that agglomerated nano-grains of carbonized PANI were distributed on the graphite felt fibers. Nitrogen adsorption analysis confirmed that the carbonized PANI-graphite felt electrode had a higher specific surface area than the pristine graphite felt.The performance of a ZIFB using a carbonized PANI-graphite felt positive electrode, and a copper foil negative electrode was evaluated by cycling for over 100 cycles. Stable cycling was observed, with a coulombic efficiency of 99%. When compared with using pristine graphite felt on the negative and positive electrodes, a significant improvement in the charge-discharge energy efficiency of around 10 % (from 67 % to 76%) was obtained.

In situ tailoring the morphology of In(OH)3 nanostructures via surfactants during anodization and their transformation into In2O3 nanoparticles

The present work reports the effect of various surfactants on the morphology of In(OH)3 nanostructures prepared via anodization. In-sheets were anodized in an environmentally benign electrolyte containing a small quantity of CTAB, CTAC, and PDDA surfactants at room temperature. The produced nanostructures were characterized using XRD, HRTEM, SAED, and EDAX. The morphology of indium hydroxide (In(OH)3) nanostructures was successfully tailored in situ with the help of surfactants in 1 M KCl aqueous electrolyte. XRD results confirmed the formation of In(OH)3 and indium oxyhydroxide (InOOH) nanostructures in the pristine form which were transformed into single-phase cubic In2O3 nanoparticles (NPs) after calcination. HRTEM analyses showed that the morphology and size of the In(OH)3 nanostructures can be tuned to form nanorods, nanosheets and nanostrips using different surfactants. The results revealed that CTAC and PDDA surfactants have a profound effect on the morphology of In(OH)3 nanostructure compared to CTAB due to the higher concentration of Cl− ion. The possible mechanism of surfactants effect on the morphology is proposed. Furthermore, annealing converted the In(OH)3 nanostructures into spherical In2O3 NPs with uniform and homogeneous size. We anticipate that the morphology of other metal-oxides nanostructure can be tuned using this simple, facile and rapid technique. In2O3 NPs prepared without and with CTAB surfactant were further explored for the non-enzymatic detection of hydrogen peroxide (H2O2). Electrochemical measurements showed enhanced electrocatalytic performance with fast electron transfer (∼2s) between the redox centers of H2O2 and electrode surface. The In2O3 NPs prepared using CTAB/Au electrode exhibited about 4-fold increase in sensitivity compared to the bare Au electrode. The biosensor also demonstrated good reproducibility, higher selectivity, and increased shelf life.

Enhancement in performance of supercapacitor using eucalyptus leaves derived activated carbon electrode with CH3COONa and HQ electrolytes: A step towards environment benign supercapacitor

Abstract The present work specifies capacitive characteristics of supercapacitors built from electrodes derived from biomass (viz., Eucalyptus leaves) and environment-friendly electrolytes. Activated carbon is derived from eucalyptus leaves and used as electrodes. The electrolytes used are environment benign electrolyte sodium acetate (1 M CH3COONa) (free from harmful F- and S- compounds) and CH3COONa added hydroquinone (HQ-redox additive). A chemical activation approach (ZnCl2–KOH) was adopted to synthesize the activated charcoal. Further, it was characterized using BET, XRD, RAMAN, SEM, and FTIR techniques. The specific BET surface area of activated charcoal is found to be 2639 m2 g−1. The performance characteristics of the supercapacitor cells were characterized by cyclic-voltammetry, charge-discharge, and electrochemical impedance spectroscopy techniques. It was observed that the supercapacitor cell utilizing pristine electrolyte CH3COONa shows a specific capacitance of 213 F g−1 and a corresponding energy density of 16.2 WhKg−1 at a specific current of 0.75 A g−1. Interestingly, the values of specific capacitance and energy density increased more than 3-fold to 702 F g−1 and 47.2 WhKg−1 respectively when the electrolyte consisting of redox additives (hydro-quinone) HQ in sodium acetate solution was used. A possible reason for such a behaviour is the Faradic redox reaction between the HQ/Q redox couple. The obtained results were compared for different electrolyte systems 1 M Na2SO4 (with and without HQ) for the same electrode. It was observed that supercapacitor cells fabricated by utilizing CH3COONa based electrolyte system exhibit better capacitive performance. The optimized supercapacitor cells were also tested in a harsh environment by varying the temperature from 25 °C to 60 °C and it shows improvement in capacitive performance with increase in temperature. Cyclic stability of supercapacitor cells was also tested for up to 10,000 cycles and it shows appealing results by offering capacitive retention of more than 122% for the optimized capacitor cell.

Ionic Liquids as Environmentally Benign Electrolytes for High-Performance Supercapacitors.

Electrochemical capacitors (ECs) are a vital class of electrical energy storage (EES) devices that display the capacity of rapid charging and provide high power density. In the current era, interest in using ionic liquids (ILs) in high‐performance EES devices has grown exponentially, as this novel versatile electrolyte media is associated with high thermal stability, excellent ionic conductivity, and the capability to withstand high voltages without undergoing decomposition. ILs are therefore potentially useful materials for improving the energy/power performances of ECs without compromising on safety, cyclic stability, and power density. The current review article underscores the importance of ILs as sustainable and high‐performance electrolytes for electrochemical capacitors.

Environmentally benign non-fluoro deep eutectic solvent and free-standing rice husk-derived bio-carbon based high-temperature supercapacitors

Deep eutectic solvents (DESs) have been emerging as newer environmentally benign electrolytes for energy storage devices with the high-temperature operational capability. For the first-time, we propose ethylene glycol and tetrapropylammonium bromide based non-fluoro DESs as electrolytes for the supercapacitor. Different compositions of DESs were also evaluated. Also, the high-temperature operational capability of the proposed electrolytes was evaluated with the free-standing microporous commercial activated carbon (AC) and mesoporous rice husk-derived bio-activated carbon (Bio-AC). The maximum cell voltages of 1.3 V and 1.0 V are identified for AC and Bio-AC based supercapacitors, respectively at 25 °C. The specific capacitances of both AC and Bio-AC electrodes are ∼100 F g−1 at 0.1 A g−1. The proposed DES electrolyte can be operated at the maximum temperature of 115 °C, which is higher than the previously reported DESs (80 °C). The specific capacitance increases with increasing temperature, and the maximum specific capacitance of an electrode is 172 F g−1 at 115 °C for Bio-AC supercapacitor. Excellent long-term stability is noted after 10,000 cycles at 25 °C and 115 °C for both AC and Bio-AC supercapacitors. The supercapacitors here may be practically used in high-temperature applications.

Mechanisms of enhanced lithium intercalation into thin film V2O5 in ionic liquids investigated by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry

Room temperature ionic liquids (RTILs) attract much attention as a new type of environmentally benign electrolytes for Li-ion batteries due to their numerous interesting physicochemical properties. Here, in this paper, Li intercalation/deintercalation in presence of the N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR14TFSI) and N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI) containing 0.3 M LiTFSI, was evaluated in a thin 100 nm layer of V2O5 deposited on Al substrate by atomic layer deposition. Potentiodynamic tests performed in LiTFSI/Pyr14TFSI show a quasi-reversible Li intercalation during 10 cycles (between 2.4 and 5 V) with an average coulombic efficiency of 99%. The capacity, calculated from the 1st cycle, is found to be 182 mAh g−1, about 19% (±2%) higher than the theoretical capacity reported for V2O5 (147 mAh g−1). X-ray photoelectron spectroscopy analysis confirms that the intercalation of more than 1 mol of Li+ per V2O5 is achieved as also the possible presence of a solid permeable interface (SPI) layer on the V2O5 surface. Likewise, the Li+ in-depth distribution on the V2O5 layer after intercalation in RTILs measured by time-of-flight secondary ion mass spectrometry ion depth profiles, show small irreversible electrode modifications with the presence of lithium through the entire V2O5 layer with significant lithium trapping at the V2O5 layer/Al substrate interface.

Benchmarking Water Electrolysis Catalysts: Making the Right Comparisons

Significant growth has occurred in recent years in water electrolysis research, especially in catalyst research for the hydrogen (HER) and oxygen (OER) evolution reactions. Materials research is still essential for continuing cost reduction in electrolysis, in order to enable higher penetration of renewable technologies for hydrogen production. Currently over 95% of hydrogen is made from fossil fuels through natural gas reforming or coal gasification. However, many claims made about catalyst activity for new materials relative to state of the art are misleading at best, due to lack of understanding of device operation and the multiple factors that contribute to catalyst selection. This talk will describe some of the complex interactions that need to be considered, and the importance of working with industry in vetting the true potential of new materials and working on the right scientific challenges. First, there are misconceptions in the literature around the highest activity catalysts today. While platinum is a clear benchmark for HER in both acidic and basic electrolyte, iridium/iridium oxide is not the most active catalyst in either solution. Ruthenium oxide has lower overpotential than iridium oxide in acid, but is not as stable as iridium at the typical cell voltages for industrial electrolyzer systems. Similarly, in basic solutions, nickel-based catalysts have been used in commercial alkaline electrolyzers for decades. Many of these catalysts have lower activation potential than iridium oxide for OER in concentrated potassium hydroxide, which is used as the electrolyte in these legacy systems. However, translating this activity to ionomer-based systems with no supporting electrolyte has been a major challenge. Therefore, comparing rotating disk electrode (RDE) results for catalyst powders in concentrated acid or base to iridium oxide is not sufficient for determining the value of new compositions, or for claiming activity or stability improvements over the best existing catalysts. A related challenge is that to be a viable catalyst in an ion exchange membrane-based device, electrode interactions need to be considered. Catalyst materials have to be manufacturable, with sufficiently high surface area and conductivity to sustain the current densities required for commercial devices (ie at current densities well in excess of RDE). In addition, particularly for the anion exchange membrane based systems, catalyst-ionomer interactions can reduce the catalyst activity significantly vs. flooded electrolyte results. Using pH 14 electrolyte as the circulating fluid in these devices eliminates many of the advantages of translating from legacy systems to membrane-based systems. Understanding ionomer effects or leveraging more benign electrolytes such as carbonate are of higher interest to industry than introducing potassium hydroxide back into these systems. Finally, testing at realistic cell voltages and current densities is essential for credible comparisons to existing commercial catalysts.

Towards Implantable Bio-Supercapacitors: Pseudocapacitance of Ruthenium Oxide Nanoparticles and Nanosheets in Acids, Buffered Solutions, and Bioelectrolytes

Metal oxides, in particular ruthenium-based oxides, are promising electrode materials for aqueous pseudocapacitors. Strong acids or bases are favored over neutral electrolytes owing to the higher capacitance. Here we explore the pseudocapacitive behavior of ruthenium oxide nanoparticles and nanosheets in near neutral pH as an environmentally benign electrolyte. The pseudocapacitive charge storage in poorly-crystalline hydrous RuO2 nanoparticles, and highly-crystalline RuO2 nanosheets were investigated in acetic acid-lithium acetate (AcOH-AcOLi) buffered solutions. It is shown that capacitance values as high as 1,038 F g−1 can be achieved in AcOH-AcOLi buffered solutions with RuO2 nanosheets, which is 44% higher than the benchmark RuO2·nH2O in H2SO4 electrolyte (720 F g−1). Furthermore, comparable performance was obtained in phosphate buffered saline and fetal bovine serum. The mechanism of the pseudocapacitive properties is discussed based on the difference in the surface redox behavior of different RuO2 nanomaterials in acid, neutral, buffered solutions, and in weak acid.

Intumescent Multilayer Nanocoating, Made with Renewable Polyelectrolytes, for Flame-Retardant Cotton

Thin films of fully renewable and environmentally benign electrolytes, cationic chitosan (CH) and anionic phytic acid (PA), were deposited on cotton fabric via layer-by-layer (LbL) assembly in an effort to reduce flammability. Altering the pH of aqueous deposition solutions modifies the composition of the final nanocoating. CH-PA films created at pH 6 were thicker and had 48 wt % PA in the coating, while the thinnest films (with a PA content of 66 wt %) were created at pH 4. Each coating was evaluated at both 30 bilayers (BL) and at the same coating weight added to the fabric. In a vertical flame test, fabrics coated with high PA content multilayers completely extinguished the flame, while uncoated cotton was completely consumed. Microcombustion calorimetry confirmed that all coated fabric reduces peak heat release rate (pkHRR) by at least 50% relative to the uncoated control. Fabric coated with pH 4 solutions shows the greatest reduction in pkHRR and total heat release of 60% and 76%, respectively. This superior performance is believed to be due to high phosphorus content that enhances the intumescent behavior of these nanocoatings. These results demonstrate the first completely renewable intumescent LbL assembly, which conformally coats every fiber in cotton fabric and provides an effective alternative to current flame retardant treatments.

Organometallic Electrochemistry Based on Electrolytes Containing Weakly-Coordinating Fluoroarylborate Anions

Electrochemistry is a powerful tool for the study of oxidative electron-transfer reactions (anodic processes). Since the 1960s, the electrolytes of choice for nonaqueous electrochemistry were relatively small (heptaatomic or smaller) inorganic anions, such as perchlorate, tetrafluoroborate, or hexafluorophosphate. Owing to the similar size-to-charge ratios of these "traditional" anions, structural alterations of the electrolyte anion are not particularly valuable in effecting changes in the corresponding redox reactions. Systematic variations of supporting electrolytes were largely restricted to cathodic processes, in which interactions of anions produced in the reactions are altered by changes in electrolyte cations. A typical ladder involves going from a weakly ion-pairing tetraalkylammonium cation, [N(C(n)H(2n+1))(4)](+), with n > or = 4, to more strongly ion-pairing counterparts with n < 4, and culminating in very strongly ion-pairing alkali metal ions. A new generation of supporting electrolyte salts that incorporate a weakly coordinating anion (WCA) expands anodic applications by providing a dramatically different medium in which to generate positively charged electrolysis products. A chain of electrolyte anions is now available for the control of anodic reactions, beginning with weakly ion-pairing WCAs, progressing through the traditional anions, and culminating in halide ions. Although the electrochemical properties of a number of different WCAs have been reported, the most systematic work involves fluoro- or trifluoromethyl-substituted tetraphenylborate anions (fluoroarylborate anions). In this Account, we focus on tetrakis(perfluorophenyl)borate, [B(C(6)F(5))(4)](-), which has a significantly more positive anodic window than tetrakis[(3,5-bis(trifluoromethyl)phenyl)]borate, [BArF(24)](-), making it suitable in a larger range of anodic oxidations. These WCAs also have a characteristic of specific importance to organometallic redox processes. Many electron-deficient organometallic compounds are subject to nucleophilic attack by the traditional family of electrolyte anions. With a view to testing the scope of the much less nucleophililic WCAs in providing a benign electrolyte anion for the generation of organometallic cation radicals, we carried out a series of studies on transition metal sandwich and half-sandwich compounds. The model compounds were chosen both for their fundamental importance and because their radical cations had been neither isolated nor spectrally characterized, despite many previous electrochemical investigations with traditional anions. The oxidation of prototypical organometallic compounds, such as the sandwich-structured ruthenocene and the piano-stool structured Cr(eta(6)-C(6)H(6))(CO)(3), Mn(eta(5)-C(5)H(5))(CO)(3), Re(eta(5)-C(5)H(5))(CO)(3), and Co(eta(5)-C(5)H(5))(CO)(2), gave the first definitive in situ characterization of their radical cations. In several cases, the kinetic stabilization of the anodic products allowed the identification of dimers or unique dimer radicals having weak metal-metal bonds and provided new preparative options for organometallic systems. In terms of thermodynamic effects, the lower ion-pairing abilities of WCAs and their good solubility in a broad range of solvents, including those of lower polarity, permitted a systematic study that yielded an integrated model of how to use solvent-electrolyte combinations to manipulate the E(1/2) differences of compounds undergoing multiple electron-transfer reactions. Although the efficacy of WCA-based electrolytes in organometallic anodic chemistry is now established, WCAs might further expand applications of organic redox chemistry. Other WCAs, including those derived from carboranes and fluorinated alkoxyaluminates, merit additional studies.

Electrodeposition of maghemite (γ-Fe2O3) nanoparticles

Crystalline maghemite (-Fe2O3) nanoparticles were cathodically electrodeposited at room temperature from environmentally benign electrolytes. The shape, size, and production rate of nanoparticles were strongly influenced by electrochemical conditions (e.g. FeCl3 concentration, current density). X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis indicated that randomly oriented polycrystalline maghemite nanoparticles were synthesized with the (3 1 1) and (4 4 0) peaks as the main diffraction peaks. Transmission electron microscopy (TEM) images revealed that average particle size decreased from approximately 23 to 7 nm with increased current density. Magnetic saturation (MS) of maghemite nanoparticles was determined to be 66 emu g −1 (66 Am 2 kg −1 ) at 300 K. The present maghemite nanoparticles showed a greater As(V) adsorption compared to iron nanoparticles, which might be attributed to a higher specific surface area.

Electrochemical fatigue sensor response to Ti–6 wt% Al–4 wt% V and 4130 steel

Some of the finer details concerning electrochemical–mechanical interactions under cyclic stressing, observed by the electrochemical fatigue sensor (EFS), are reported, with emphasis on a series of ramp-and-hold cyclic tests on samples of hardened Ti–6 wt% Al–4 wt% V and 4130 steel. These tests were designed to further our understanding of the mechanisms underlying EFS response by revealing its timing and morphology, as well as any dependence on stress range, strain rate or mean stress. The EFS is an instrument that monitors an electrochemical current (‘the EFS current’) as a means of investigating fatigue damage in metals; specimens are fatigued in a benign electrolyte, under controlled conditions, so that their fatigue lives do not differ from those obtained in air. The results show that cyclic loading produces a cyclic EFS current with extrema located at points in the loading cycle where the strain rate is highest. Localized fatigue straining and crack-associated plasticity enhance the EFS current, producing peaks that reveal information about the timing and magnitude of plastic response on a cycle-to-cycle basis. The response depends on the cyclic variables studied in a manner that is convenient for experimentation. The EFS current reflects the superposition of two basic components: one is correlated with elastic strain and is becoming better understood; the other is directly related to plasticity.