Potentiostatic Measurements Research Articles

Hydrogen Bubble Templating of Fractal Ni Foams for Water Oxidation in Alkaline Media

Dynamic Hydrogen Bubble Templating of Ni electrodes (NiDHBT) is applied to form fractal macroporous structures and their properties towards oxygen evolution reaction (OER) is assessed. Upon varying Ni electrodeposition conditions, morphological features with percolating porosity were finely tuned and electrochemical activity towards O2 evolution reaction (OER) in 1M KOH were enhanced. As demonstrated by cyclic voltammetry, NiDHBT electrochemical features displayed a tremendous increase (x 250) of the electrochemically active Ni surface atoms, with strong mechanical adherence to the underlying substrate. Under constant electrolysis (0.25 A cm-2), OER potentials remained stable and occurred at lower potentials (shifted by ca. 300 mV) as compared to a bare Ni plate. Contact angle measurements confirm the super-aerophobic nature of the fractal Ni films, which leads to fast and sustainable release of O2 bubbles during potentiostatic measurements. Due to the versatility of the DHBT method, fractal Ni-based, e.g. NixFe1-x, electrodes for use in advanced electrolysis cell configurations can be envisioned, to further examine transport enhancement in relevant industrial systems and its tolerance to commercial alkaline solutions.

Effect of Magnetic Field on Anodic Dissolution and Pitting of Iron in a Molybdenum Nitrate Solution with Chlorides

Magnetic fields would affect electrochemical reactions for metallic materials in aqueous solutions. The main effect of a magnetic field applied on an electrochemical system is the introduction of additional forces on the ions in the electrolyte, such as Lorentz-force driven magnetohydrodynamics (MHD) effect and Kelvin-force-driven magnetic field gradient force (MFGF) effect. There are some published reports on the influence of magnetic fields on the pitting corrosion, and apparently contradictory results have been reported. In this work, we focused on the effect of magnetic field on anodic dissolution of iron in a molybdenum nitrate solution with chloride ions. The typical potentiodynamic polarization curves of iron in a 0.2 mol L-1 Na2MoO4 +0.2 mol L-1 NaCl solution at a potential sweep rates of 0.833 mV/s and under 0 T and 0.4 T magnetic field are shown in Fig. 1. Magnetic field decreased the limiting current densities at high potentials. The results in Fig. 1 were confirmed by potentiostatic polarization measurements, which were used to study the effect of magnetic field on the anodic corrosion of iron. After a relatively long period of polarization at 0.4V(SCE) at 0T, imposing a magnetic field will result in a sudden increase and then a slowly decrease of the current density, as shown in Fig. 2(a). The electrode surface morphologies after potentiostatic polarization at 0.4V for 200s under 0T are shown in Fig. 2(b), which are corresponded to the conditions in Fig. 2(a). The pits have propagated deeply. The mass transfer process between occluded pit bottom and the pit mouth would became difficult with the deepening of the pits. The retarding effect of magnetic field on anodic dissolution of iron in a molybdenum nitrate solution with chloride is ascribed to its effect on the mass-transport process between the occluded pit bottom and the pit mouth and finally the resultant disturbance of the autocatalysis process involved in pitting Figure 1

Measurement of Non-Linear Impedances and Zero Free Parameter Modeling Approach for Predicting Battery Voltages

Choosing the appropriate energy storage system for a given application is one of the most important and deciding issues that need to be tackled in designing electric powered equipment. In particular, for electric vehicles, a plethora of power consumption regimes are described by regulatory bodies. These power consumption profiles can be easily transformed to current requirements of the energy storage system which results in countless such current profiles. The problem is further complicated with the vast variety of available energy storage systems, that all need to be tested for a given application specified by the required current profile. Therefore, rather than testing every single combination, modelling approaches are utilized to predict various combinations. Models in the literature usually employ impedance measurements as their basis, either to obtain relevant parameters for a first principles model or to fit an equivalent circuit which is subsequently taken to the time domain. In our modelling approach[1], the current profile to be modeled is converted to the frequency domain via a Fourier Transform. This frequency domain profile is multiplied by the impedance at each frequency, yielding a voltage response again in the frequency domain. This frequency domain voltage is then inverse Fourier transformed to obtain the time domain voltage response. After correcting for the state of charge with a simple DC discharge map, the voltage response of any electrochemical storage system can be obtained with errors less than 1%[1,2]. The developed modelling approach does not fit any models to the impedance data, thus has no free parameters. Thus, modeling battery systems require the accurate measurement of impedance in both our method [1,2]and others. In order to acquire an accurate impedance spectrum, the system needs to be stable throughout the measurement and the sine wave applied needs to lead to a linear response. The impedance spectrum measured can either have non-linearities due to the high amplitude used, or due to the chemistry of the system being irreversible. In either case, the measured impedance and/or the response of the battery would have contributions due to non-linearities. EIS assumes linearity which is usually valid for small amplitudes (of both voltage and current) for energy storage systems. In real applications, however, larger amplitudes are required from these systems which is not easily modeled using equivalent circuit models. In our approach, however, the non-linearities can be accounted for by simply adding the relevant harmonics to the otherwise linear impedance data. We will show the applicability of our model for nonlinear systems using a supercapacitor under high current loads. For the latter case, a primary chemistry, SOCl2 is investigated. In the literature the impedance of SOCl2 batteries is ill-characterized where the reports either have obvious non-linearities[3] or omit data [4]. If the following half reactions and the resulting total reaction is considered for the chemistry, a cell potential that is independent of any concentration is seen, which causes the cell voltage to stay constant at around 3.6V (minus a small decrease due to i.R) as shown in Figure a. Li(s) --> Li+(dis.) + e- (Anode) 4Li+(dis.)+ 4e- + 2SOCl2 (l)--> 4LiCl(s) + SO2 (g)+ S(s) (Cathode) Even a small perturbation such as the small amplitude voltage signal of a potentiostatic impedance measurement is not viable, where in the discharge region the cell potential drops below 3.6V only at full discharge and in the charge region, the reaction is not defined. Utilizing a galvanostatic measurement with a DC offset and dynamic adjustment of the measurement parameters, we will show Kramers-Kronig transformable impedance data for SOCl2 batteries as shown in Figure b.

Temperature Path Dependent Voltage and Thermal Expansion Hysteresis in Li-Ion Cells

Recently, lithium-ion batteries have become a key player in the field of energy storage for various applications ranging from mobile phones to electric vehicles. Whilst the next reliable storage technology is long in coming, the improvement of the lithium-ion battery performance is usually conducted on the system level, utilizing the exact knowledge of thermal and electrical properties of the cells. Consequently, the optimal operation of the battery system relies on the precise cell characterization. Knowledge of reversible and irreversible heat generation processes occurring in lithium-ion cells is inevitable for a proper design of thermal management systems. The determination of reversible heat is often carried out by means of a potentiostatic measurement of entropy related effects, which are based on structural properties of the active materials. This method utilizes the assumed linear relationship between a change in the open-circuit potential (OCP) of a cell for a change in its temperature. In this work, the potentiostatic method is more closely investigated regarding this linear relationship and possible associated measurement inaccuracies of entropic coefficients. Various lithium-ion cells with differing chemistries and cell designs are investigated in this study. All cells were rested for more than six months at different States of Charge (SOC) at room temperature in order to guarantee a most equalized state. The chosen generic temperature excitation was composed of a positive and a consequent negative temperature pulse, both starting at a base temperature of 25 °C. Profile I is formed of temperature pulses with varying pulse length whereas within Profile II, the pulse amplitude was varied. After each temperature change, new entropic coefficients were calculated based on the preceding data. Additionally, the thickness of selected cells was monitored via 2D laser scan during Profile I and Profile II. The results obtained in this work clearly reveal a non-linear behaviour of the voltage to temperature relationship regardless of the cell design, SOC, cell chemistry or sign of the derived entropic coefficient. This non-linearity manifests in a certain hysteresis of the OCP depending on the temperature history of the cells (i.e. Profiles I and II). Preliminary results from the thickness experiment also reveal a hysteresis in the thermal expansion, which we assume is the reason for the non-linear behaviour of the voltage. An improvident determination of the entropic coefficients might lead to a relative deviation of up to 95%, resulting in inacceptable errors in the design of thermal management systems. In order to limit the measurement inaccuracies we suggest to minimize the temperature pulse duration whilst still allowing for a thermal equalization of the cell. Furthermore, we suggest to minimize the amplitude of the temperature pulse as much as possible, whilst still allowing for an acceptable Signal to Noise Ratio (SNR) for the measured voltage response.

Electrocatalytic Activity of Amorphous Ni-Nb-Y Alloys for the HER in Alkaline Water Electrolysis

The recent development of anion exchange membranes (AEM) has renewed interest in alkaline water electrolysis for large-scale production of hydrogen gas. New electrocatalysts are required to interface with such AEMs in advanced alkaline water electrolyser designs. The present work assesses the role of structure and chemistry on the catalytic activity of cryomilled Ni-Nb-Y amorphous alloys towards the hydrogen evolution reaction. X-ray diffraction and TEM studies characterized the microstructure of the Ni-Nb-Y catalysts. Kinetic data from potentiostatic polarization and EIS measurements support the hypothesis of enhanced activity resulting from the multiphase catalyst structure. The novel multiphase Ni81.3Nb6.3Y12.5 catalyst displayed the greatest catalytic activity. This improvement is attributed to the presence of a crystalline Ni5Y secondary phase finely dispersed in the yttrium-rich Ni-Nb-Y amorphous matrix. The results herein demonstrate that mechanically alloyed Ni-based amorphous-based materials are promising catalysts for electrochemical hydrogen production.

Ni0.85Co0.15WO4 nanosheet electrodes for supercapacitors with excellent electrical conductivity and capacitive performance

Monoclinic wolframite Ni1-xCoxWO4 (x = 0 and 0.15) nanosheets are synthesized successfully through chemical co-precipitation. The specific surface area increases appreciably with reduced pore radius when Co2+ ions are incorporated into the NiWO4 lattice. In comparison with NiWO4, the band gap of Ni0.85Co0.15WO4 reduces with the electrical conductivity increased threefold. The electrochemical properties and the device performance of supercapacitors with Ni1-xCoxWO4 as electrodes are characterized via the potentiostatic and galvanostatic cycle measurements, and electrochemical impedance spectroscopy (EIS). The Ni0.85Co0.15WO4 electrode exhibits an obvious increase in specific capacitance, six-fold higher than that of NiWO4 electrode at a current density of 0.5 A g−1. Ni0.85Co0.15WO4 electrode also shows excellent rate performance with ~78% capacitive retention while the current density is enhanced fivefold. The possible mechanism for the improved electrical conductivity and capacitive performance due to the incorporation of Co2+ to NiWO4 lattice has been discussed.

Time-dependent Enhanced Corrosion of Ti6Al4V in the Presence of H2O2 and Albumin

There is increasing concern regarding the biological consequences of metal release from implants. However, the mechanisms underpinning implant surface degradation, especially in the absence of wear, are often poorly understood. Here the synergistic effect of albumin and H2O2 on corrosion of Ti6Al4V in physiological saline is studied with electrochemical methods. It is found that albumin induces a time-dependent dissolution of Ti6Al4V in the presence of H2O2 in physiology saline. Potentiostatic polarisation measurements show that albumin supresses dissolution in the presence of H2O2 at short times (<24 h) but over longer time periods (120 h) it significantly accelerates corrosion, which is attributed to albumin-catalysed dissolution of the corrosion product layer resulting in formation of a thinner oxide film. Dissolution of Ti6Al4V in the presence of albumin and H2O2 in physiological saline is also found to be dependent on potential: the titanium ion release rate is found to be higher (0.57 µg/cm2) at a lower potential (90 mV), where the oxide capacitance and resistance inferred from Electrochemical Impedance Spectroscopy also suggests a less resistant oxide film. The study highlights the importance of using more realistic solutions, and considering behaviour over longer time periods when testing corrosion resistance of metallic biomaterials.

Localized Corrosion: Passive Film Breakdown vs Pit Growth Stability: Part II. A Model for Critical Pitting Temperature

Potentiostatic temperature-scanned experiments were performed on 316L stainless steel and revealed that both the measured values of critical pitting temperature (CPT) and their distribution ranges increased with the decrease of the aggressiveness of exposure conditions. Previous models for CPT cannot explain these observations, so a model for CPT is proposed based on criteria for pit growth stability with added effects of the passive film breakdown. The criterion for pit stability is assumed to be the maintenance of a critical pit solution concentration at the pit surface, which requires the maximum pit dissolution current density to be equal to or greater than the diffusion current density associated with this critical concentration. The resulting model can explain many observations of nature of the CPT. The CPT is shown not to be a single-valued critical value; instead, it is a statistically distributed value based on the detailed behavior of many pitting events. For potentiostatic measurements, the measured CPT is just the temperature at which the first stable pit forms. The commonly recognized and tightly distributed CPT is determined from the perspective of pit growth stability and it represents the temperature with the highest probability to form the first stable pit.

Electrochemical performance of highly active ceramic symmetrical electrode La0.3Sr0.7Ti0.3Fe0.7O3-δ-CeO2 for reversible solid oxide cells

The electrolyte supported cells with the La0.3Sr0.7Ti0.3Fe0.7O3-δ (LSTF0.7)-CeO2|ScSZ (scandia-stabilized zirconia)|La0.3Sr0.7Ti0.3Fe0.7O3-δ-CeO2 symmetrical configuration are fabricated by infiltration method and investigated as reversible solid oxide cells (RSOCs) at different CO/CO2 ratios. A well-deposited microstructure is observed in the infiltrated electrode. From the I–V curves, the maximum current density of 1.90Acm−2 at 2.0V is obtained for CO: CO2 ratio of 1: 1 for CO2 electrolysis at 850°C, while the corresponding power density under the same conditions is 357mWcm−2 in fuel cell mode. Electrochemical impedance spectroscopy (EIS) is conducted for better understanding the electrode catalytic mechanism. The whole symmetrical cell achieves the polarization resistance (Rp) values of 0.284 and 0.203Ωcm2 at 850°C under open circuit and at 1.4V, respectively. Under reversible operation (cyclic voltammetry) at 800°C, no distinct degradation is found in the cell with the infiltrated LSTF0.7 symmetrical electrodes. The long-term stability at 1.2–2.0V characterized by potentiostatic measurement indicates that the prepared LSTF0.7-CeO2 composite electrode is comparatively stable at low voltages while a degradation behavior is observed at high voltages. These results illustrate that the LSFT0.7-CeO2 composite is a promising active ceramic electrode for symmetrical RSOCs.

Time-Resolved Luminescence Spectroelectrochemistry at Screen-Printed Electrodes: Following the Redox-Dependent Fluorescence of [Ru(bpy)3]2.

In this work, a compact instrument for time-resolved luminescence spectroelectrochemistry using low-cost disposable electrodes is reported. This instrument can be coupled with screen-printed electrodes via a specific cell and a reflection probe, which allows one to observe changes occurring at the electrode/solution interface. This approach allowed one to follow the fluorescence variation of electrofluorochromic species such as [Ru(bpy)3]2+ at screen-printed carbon electrodes. A strong correlation between the electrochemical processes and the fluorescence was found during potentiostatic or multipulsed amperometric measurements. A decrease of the fluorescence was observed when the [Ru(bpy)3]2+ was oxidized to [Ru(bpy)3]3+ and part of this fluorescence is recovered when [Ru(bpy)3]3+ was reduced to the initial species. Moreover, a significant increment of the fluorescence was found when the oxygen reduction reaction takes place, which also confirms its quenching effect. Finally, multipulsed amperometric detection was employed in order to obtain more information about the redox-dependent luminescence of [Ru(bpy)3]2+ finding a continuous quenching over time attributed to bleaching chlorine-based species.

(Keynote) Formate/Formic Acid Synthesis from CO2 Electroduction Using Bi and Pb Nanostructures

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. Pb and Bi are promising catalysts with good selectivity for formate. Bismuth is non-toxic and has negligible environmental impact. It has few commercial applications, and its price has been low and relatively stable in recent years. In the case of Lead, it can be prepared in the form of dendrites with nanometre-sized tips. Local high electric fields can exist at the tip of these dendrites that can induce a concentration of electrolyte which in turn leads to a high local concentrations of CO2. In this study, we compared the activity and stability for CO2 electroreduction of high surface area metallic Bi and Pb films. In both cases, the materials films were prepared through a direct electrodeposition (potentiostatic method). Both types of films were extensively characterised 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

Corrosion Behavior of Recycling Al- Alloy Based Metal Matrix Composites Reinforced by Nano particles

The present work aims to preparation and investigation of the corrosion behavior of recycling Al alloy based metal matrix composite reinforced with nano SiC with weight percentage (2%, 4%, 6%, and 8%) and particle size 52 nm were evaluated. The composites were fabricated using liquid metallurgy (stir casting process). The corrosion rates of composites were calculated using potentiostatic measurements in 3.5% NaCl solution.. The results showed that Al/SiC nanocomposites have higher corrosion resistance than aluminum matrix.The corrosion resistance was found to be increased by increasing of the weight percentage of the nanoparticles The Al/8% nano (SiC)P composites exhibited the highest corrosion resistance among all the investigated nanocomposites. The microstructure indicate that the strong interfacial bonding between the matrix alloy and reinforcement.

Theoretical model and its verification for the effect of sand concentration on the critical flow velocity for erosion–corrosion of 304 stainless steel in 3.5 wt.% NaCl solution

A theoretical model based on fluid dynamics and mechanical analyses was proposed to explain the relationship between the critical flow velocity (CFV) and sand concentration which indicated that the CFV followed a power law of ，i.e. CFV varied with Cm as a power function with exponent of −0.5. Potentiostatic polarisation measurements were performed on 304 stainless steel during the erosion–corrosion process to validate the model. The erosion–corrosion tests were conducted at various flow velocities between 0 and 17 m s−1 and four silica sand concentrations of 2–5 wt.% under the impingement of sand-containing NaCl solution at an impact angle of 90°. It was observed that the anodic current density under a controlled potential increased significantly when the flow velocity was above a critical value. The CFV values of 304 stainless steel under impingement by NaCl solution containing 2–5 wt.% sand are 14, 111, 9 and 8 m s−1, respectively. The experimental results showed that the CFV did follow a power law of sand concentration, while the exponent deviated from the theoretical predicted result. The deviation was attributed to the difference between the actual impact velocity and the inlet flow velocity according to the calculated results by the computational fluid dynamics (CFD) model. And the corrected CFV followed a power law of which was in consistence with the predicted result ().

Partial electronic conductivity of nanocrystalline Na2O2

Understanding charge carrier transport in Na2O2, being one of the possible storage materials in the non-aqueous Na–O2 battery, is key to the development of this type of energy storage system. The electronic and dynamic properties of Na2O2 are expected to greatly influence the overall performance and reversibility of the discharge process. Thus far experimental studies on this topic are rare. To measure the extremely low conductivities setups with sufficiently high sensitivity are needed. Here we studied the partial electronic conductivity σeon of nanocrystalline Na2O2 by potentiostatic polarization measurements which we carried out at room temperature. σeon turned out to be in the order of 8.8 × 10−14 S cm−1; with a very poor total conductivity of σtotal = 17 × 10−14 S cm−1 we obtained σtotal/σeon ≈ 2 clearly showing that ionic transport of Na ions is strongly coupled to electronic dynamics.

Effect of the elastic tensile load on the electrochemical corrosion behavior and diffusible hydrogen content of ferritic steel in acidic environment

Linear polarization resistance (LPR) and potentiostatic polarization measurement are employed to determine the influence of tensile stress in the elastic range on the electrochemical corrosion and hydrogen reduction behavior of ferritic steel in a sour environment. For a more mechanistic study, the experimental polarization data were fitted using the Wagner-Traud equation, and the reaction parameters related to the sour corrosion of ferritic steel under an applied load condition were obtained. This study revealed that elastic loading condition led to higher anodic and cathodic reactions of the steel, resulting in a significant increase in corrosion current and a decrease in polarization resistance. In particular, the hydrogen evolution rate induced by the cathodic reduction reaction increased significantly under an applied elastic load. The generation of molecular hydrogen in the pre-formed sulfide film can contribute to weakening the stability of the sulfide film by suppressing normal growth of the film. Consequently, the diffusible hydrogen contents in the steel increases under the stress condition, resulting in a higher susceptibility to hydrogen assisted cracking failure.

Electron Trap States and Photopotential of Nanocrystalline Titanium Dioxide Electrodes Filled with Single‐Walled Carbon Nanotubes

AbstractHybrid film electrodes were made of nanocrystalline titanium dioxide (TiO2) and various percentages of single‐walled carbon nanotube (SWCNT) fillers up to 5.5 wt%. A complete photoelectrochemical study was performed in both alkaline and acidic conditions by using cyclic voltammetry, potentiostatic photocurrent measurements, and open‐circuit‐potential measurements under UV/Vis irradiation. Dark voltammograms show a transition from a capacitive to a resistive behavior in the TiO2accumulation region upon increasing SWCNT percentages. In addition, the energy levels of deep electron traps change inside the TiO2bandgap. The new peak positions correspond to the reduction potentials of SWCNTs, and their associated charge capacities increase with the SWCNT percentage. The modifications observed in dark experiments directly impact on the shape profile of cyclic voltammograms under irradiation. As a consequence, reduction potentials of SWCNTs appear near the cathodic peaks of certain water oxidation intermediates, and may be interacting with them. On the other hand, open‐circuit photopotentials reach maximum values for small SWCNTs percentages around 0.02 wt%. An increase in potentiodynamic and potentiostatic photocurrents is observed for the electrode containing 0.02 wt% SWCNTs, compared to reference TiO2in acidic conditions.

Integration of electrochemical and synchrotron-based X-ray techniques for in-situ investigation of aluminum anodization

Anodization of aluminum alloys AA 6082 and AA 7075 was investigated in-situ with integrated electrochemical and synchrotron-based X-ray reflectivity (XRR) methods providing complementary information about the anodic processes taking place on the alloys. The stepwise potentiostatic polarization measurements reveal dynamic processes of the anodic oxide formation and dissolution, and the following electrochemical impedance spectroscopy measurements detect the break of the native oxide and the growth of typical two-layer anodic oxide film, while the XRR measurements show the growth of entire anodic oxide film whose thickness increases linearly with the increasing applied potential. The results indicate that while a stable anodic oxide can be formed on the both alloys with a similar growth factor, AA 7075 shows a thinner thickness of the barrier layer and a lower resistance of the oxide film. The electrochemical results suggest both localized and uniform anodic dissolution processes, which are more pronounced on AA 7075, demonstrating the effect of alloying elements on the growth of anodic oxides.

Vibrational, electrical, and ion transport properties of PVA-LiClO4-sulfolane electrolyte with high cationic conductivity

Novel solid polymer electrolytes, poly(vinylalcohol)-lithium perchlorate (PVA-LiClO4) and PVA-LiClO4-sulfolane are prepared by solvent casting method. The experimental results show that sulfolane addition enhances the ionic conductivity of PVA-LiClO4 complex by three orders. The maximum ionic conductivity of 1.14 ± 0.20 × 10−2 S cm−1 is achieved for 10 mol% sulfolane-added electrolyte at ambient temperature. Polymer-salt-plasticizer interactions are analyzed through attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Lithium ion transference number is found by AC impedance spectroscopy combined with DC potentiostatic measurements. The results confirm that sulfolane improves the Li+ transference number of PVA-LiClO4 complex to 0.77 from 0.40. The electrochemical stability window of electrolytes is determined by cyclic voltammetry (CV). The broad electrochemical stability window of 5.45 V vs. lithium is obtained for maximum conducting electrolyte. All-solid-state cell is fabricated using maximum conducting electrolyte, and electrochemical impedance study is carried out. It reveals that electrolyte interfacial resistance with Li electrode is very low. The use of PVA-LiClO4-sulfolane as a viable electrolyte material for high-voltage lithium ion batteries is ensured.

Understanding the Influence of the Biomass-Derived Alcohols on the Activity and Stability of Pt Nanoparticles Supported on Graphene Nanoribbons

We produced Pt/GNRs by a one-step synthesis procedure and evaluated their electroactivity and stability towards glycerol electrooxidation reaction (GEOR) for the first time. We compared the electrocatalytic performance of GEOR with methanol and ethanol electrooxidation on Pt/GNRs at identical experimental conditions. The activities and stabilities for the electrooxidation of these biomass-derived alcohols on Pt/GNRs were compared to commercial Pt/C. The synthesis of the Pt/GNRs was confirmed by transmission electron microscopy, x-ray diffractometry, ultraviolet spectrophotometry, and Raman spectroscopy. We found that the activities of Pt/GNRs for these reactions are comparable to Pt/C, with improvement in terms of current density for methanol electrooxidation. Comparing potentiostatic measurements, we found that glycerol produces lower pseudo-stationary current densities than ethanol and methanol on both catalysts, with greatest values found for methanol electrooxidation on Pt/C. Otherwise, the GNRs remarkably enhance the stability of the catalyst for all the reactions, by increasing the stability of the current density during successive potential cycles, and by preventing the loss of electrochemically active surface area by avoiding carbon corrosion and Pt detachment. Moreover, we showed that the stability of the NPs depends on the biomass-derived alcohol used. The solution containing methanol reveals itself the most aggressive electrochemical environment to the catalyst, impacting in the decrease of surface area, while glycerol is less aggressive. Hence, the different products formed at the interface electrode/solution might lead to a different electrochemical environment, which plays an important role on the stability of the catalysts.

Effect of benzamide on the corrosion inhibition of mild steel in sulphuric acid

The effect of benzamide as a chemical inhibitor on mild steel corrosion in 0.5M H 2 SO 4 was studied at ambient temperature. The experimental work was performed with gravimetric and potentiostatic polarization measurement methods. Potentiostatic polarization measurement was performed with a potentiostat (Autolab PGSTAT 30ECOCHIMIE) interfaced with a computer for data acquisition and analysis. The benzamide inhibitor achieved very effective corrosion inhibition of the steel specimens in the H 2 SO 4 test medium. The inhibition performance increased with increasing concentration of the inhibitor. Benzamide’s best performance was achieved with the 4 g 200 mL –1 H 2 SO 4 concentration and closely followed by the 3 g 200 mL –1 of the H 2 SO 4 . In 0.5 MH 2 SO 4 , the 4 g and 3 g 200 mL –1 H 2 SO 4 gave the optimal performance with weight loss of 2.99 g at 480 h of the experiment, respectively. The corrosion rate for 4 g’s was 6.4mmyr –1 . The experiment also achieved polarization resistance values of 3.98 and 2.37E+01 Ω ; corrosion rate,CR, of 7.48E+00 and 1.26E+01mmyr –1 and current density (Icorr) values of 6.45E–04 and 1.08E – 03A cm –2 , respectively. The corrosion inhibition efficiency values are, respectively, 60 and 70 % for both 3 g and 4 g 200 mL –1 H 2 SO 4 concentrations at 48 h.Results of ba and bc indicated a mixed type inhibitor. Benzamide adsorption on the steel’s surface obeys the Freundlich adsorption isotherm. Keywords: Electrochemical corrosion, benzamide, inhibitor, sulphuric acid, mild steel, polarization