Electrolyte Medium Research Articles

Simple electrochemical sensors for highly sensitive detection of gaseous hydrogen peroxide using polyacrylic-acid-based sensing membrane

In this study, we present a simple electrochemical sensing platform for the detection of low concentration levels of gaseous hydrogen peroxide (H2O2). The sensors were designed using a supporting screen-printed electrode system modified with a polyacrylic-acid-based (PAA) sensing membrane that serves simultaneously as an electrolyte and accumulation medium. We prepared and compared two types of sensors, i.e., (i) PAA sensor and (ii) MnO2/PAA sensor with a MnO2 pre-modified working electrode surface. Both sensors exhibited good electroanalytical performances for detecting trace levels of gaseous H2O2 with the limits of detection of 3 μg m−3 (MnO2/PAA sensor) and 2 μg m−3 (PAA sensor), a linear response in the examined concentration range of 15–121 mg m−3, and repeatability with RSDs of 10.4% (MnO2/PAA sensor) and 4.7% (PAA sensor). The practical applicability of both sensors was successfully demonstrated by detecting gaseous H2O2 in the real environment, i.e., in a room that was disinfected with 10% H2O2 solution.

Textural characteristic of anodized aluminium foil for thermal energy storage application

Due to increase in energy consumption it is important for researcher to develop an efficient thermal energy storage fluid that capture heat for electricity production system via thermal solar applications. The aim of this research is to investigate and optimized the anodization parameter to synthesize aluminium oxide film on aluminium foil, which is the primary component of the nanoparticle thermal energy storage fluid. The temperature used for the formation of film via anodization procedure was 281 K to 297 K. A Box–Behnken design method was adopt to design experiments and analysis statistical information based on experimental input. The output response of the derived polynomial equation was found to fit well with experimental data with R2 equalled​ to 0.98 and demonstrated insignificant lack of fit. From the ANOVA results, it is clear that temperature and concentration are significant parameters. As temperature and concentration changes the hardness of aluminium oxide film ranged between 169 to 201. An increase in temperature support the movement of charge along the electrolyte medium which promote the formation of oxide film in the solution. Results illustrated the ectothermic activity of the anodization reaction and the electric current movement in thing aluminium film. Future work will need to be conducted to fabricate nanoparticle from the aluminium oxide film obtained from this experiment.

Morphological insights associated to instantaneous nucleation and growth in Cr(III) electrodeposition on nickel in aqueous media

In this work, experimental evidence of instantaneous nucleation and growth transients were observed for Cr(0) electrodeposits in aqueous electrolytes, using Cr(III) as precursor species in a double potential step process. This progression occurs via a Cr(II) intermediate, which should be stabilized in aqueous media to afford its proper reduction. This mechanism is rarely observed in aqueous media due to rapid onset of hydrogen evolution and adsorption due to both the acidity and chemical composition of the electrolytic medium employed. Using this approach to prepare a potentiostatically controlled electrodeposit, afforded functional coating on a substrate which is employed for industrial applications (Ni). The morphological features observed from microscopic analysis of the surfaces allowed considering that such instantaneously formed nuclei are important in determining the grain size of the final coating and as such could be controlled in a more significant way with this potentiostatic technique, providing an alternative to the galvanostatic classic approach.

Study of Crown Ether - Lithium Salt Complexes for Solid-State Electrolyte of Li Ion Battery

Electrolyte plays a pivotal role in Li-ion battery (LIB). Generally, it has been considered as a liquid phase material that allows for reasonable dissolution ability of inorganic salt and ion transportability across the electrodes. Since conventional liquid electrolytes faced limitations to improve battery performance, the solid-state electrolyte has raised rapidly to replace the liquid electrolyte. Solid polymer electrolyte (SPE) is one of the most promising solid-state electrolytes, it has attracted attention due to its strength as an electrolyte such as high accessibility, tolerance against volume change of electrodes, and reasonable chemical/thermal stability. Especially poly(ethylene oxide) (PEO) or PEO-based electrolytes have been widely developed, because of their outstanding Li salt dissolution ability. PEO forms a unique helical complex structure with Li salt, the complex is highly stable. It allows PEO to dissolve Li salt much easier than other polyethers, such as poly(propylene oxide) or poly(oxymethylene). However, the high stability of the complex could disturb fast ionic conduction in electrolyte medium, it is the reason why PEO electrolyte has poor ionic conductivity at ambient temperature (10-7 to 10-6S/cm at room temperature). Crown ethers, the macrocycles composed of ethylene oxide, also attract attention for SPEs. Even though the monomer is the same (ethylene oxide) for both PEO and Crown ethers, the properties of each complex are different. Crown ether electrolyte shows higher ionic conductivity than PEO electrolyte at ambient temperature, it is assumed that the crown ether electrolyte is an amorphous phase while PEO electrolyte has high crystallinity below the melting point (60~80%). Crown ether is also promising for Li metal batteries. Crown ether is the hosting material that has a preorganized acceptor structure (also well-known as macrocyclic effect), therefore it can adjust kinetics of reduction on the surface of Li metal anode. Even though promising abilities of crown ether electrolytes have been reported, their ion conduction mechanisms are yet understood well. Therefore, it is worth studying about complex structure and ion conduction mechanism of crown ether electrolyte for a better understanding of SPE, and further, it can be a milestone to design new SPEs. To understand the complex structure and ion conduction mechanism in crown ether electrolytes, we performed both experimental and theoretical analysis. We synthesized the complexes of different sizes of crown ethers (12-crown-4, 15-crown-5, and 18-crown-6) and Li salts (LiTFSI, LiClO4, LiBF4, and LiI). The complexes are characterized by Fourier transformed infrared (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA), and AC impedance analysis. DFT calculation and molecular dynamics for each complex were performed to obtain an atomistic description of the complexes.

Bismuth Oxide Decorated Silicon Photocathodes for CO2 to Formate Solar Driven Conversion

In the field of CO2 electrochemical conversion, [1] the use of semiconducting photocathodes instead of non-photoactive traditionally used electrodes (e.g., metals and carbon) could provide a real benefit in terms of energy gain because it allows the electrochemical process to be activated by photogenerated electrons. [2] In that context, silicon appears as one of the most promising semiconducting materials owing to its small bandgap (1.1 eV) able not only to harvest photons from a large portion of the solar spectrum but also to encompass the different proton-assisted multielectron reduction potentials for CO2. [3],[4],[5] Herein, we report that silicon photocathodes modified with electrodeposited Bi nanostructures are highly active for the photoelectrocatalytic conversion of CO2 to formate in aqueous electrolytic medium. p-type Si photocathodes functionalized with Bi2O3 catalyst were easily fabricated without an additive polymer layer using a one-step and fast electrodeposition method. Both composition and morphology of the deposited Bi cocatalyst could be tuned by controlling the electrodeposition time. The photocathode prepared from a 5 s electrodeposition exhibited the highest photocurrent density (-24.1 mA cm-2) with partial formate photocurrent density j formate = -17.4 mA cm-2 at -1.03 V vs Reversible Hydrogen Electrode (corresponding to a 0.84 V overpotential for CO2 to formate conversion).Such values highlight the excellent catalytic activity for CO2 electroreduction of our photocathodes, [6] outperforming that of recently reported Bi-based catalysts deposited on Si. [7] Moreover, under our conditions, the formate production rate reached 14.9 mg h-1 cm-2 with a Faradaic efficiency for formate of 72%. We anticipate that the conversion efficiency of CO2 could be further improved by using structured silicon surfaces, as recently demonstrated by ourselves for sunlight-driven water splitting, [8] and/or Bi nanostructures. [1] a) J. Qiao, Y. Liu, F. Hong, J. A. Zhang, J. Chem. Soc. Rev. 2014, 43, 631-675. b) C. Costentin, M. Robert, J. M. Saveant, Chem. Soc. Rev. 2013, 42, 2423−2436. [2] a) J. L. White, M. F. Baruch, J. E. Pander III, Y. Hu, I. C. Fortmeyer, J. E. Park, T. Zhang, K. Liao, J. Gu, Y. Yan, T. W. Shaw, E. Abelev, A. B. Bocarsly, Chem. Rev. 2015, 115, 12888–12935. b) K. Maeda, Adv. Mater. 2019, 31, 1808205. [3] K. Sun, S. Shen, Y. Liang, P. E. Burrows, S. S. Mao, D. Wang, Chem. Rev. 2014, 114, 8662−8719. [4] a) D. He, T. Jin, W. Li, S. Pantovich, D. W. Wang, G. H. Li, Chem. Eur. J. 2016, 22, 13064. b) B. Kumar, J. M. Smieja, C. P. Kubiak, J. Phys. Chem. C 2010, 114, 14220. c) B. Kumar, M. Llorente, J. Froehlich, T. Dang, A. Sathrum, C. P. Kubiak, Annu. Rev. Phys. Chem. 2012, 63, 541. [5] E. Torralba-Penalver, Y. Luo, J.-D. Compain, S. Chardon-Noblat, B. Fabre, ACS Catal. 2015, 5, 6138. [6] D. Fu, J. Tourneur, B. Fabre, G. Loget, Y. Lou, F. Geneste, S. Ababou-Girard, C. Mériadec, ChemCatChem. 2020, 12, 5819. [7] a) Q. Gong, P. Ding, M. Xu, X. Zhu, M. Wang, J. Deng, Q. Ma, N. Han, Y. Zhu, J. Lu, Z. Feng, Y. Li, W. Zhou, Y. Li, Nat. Commun. 2019, 10:2807. b) P. Ding, Y. Hu, J. Deng, J. Chen, C. Zha, H. Yang, N. Han, Q. Gong, L. Li, T. Wang, X. Zhao, Y. Li, Mater. Today Chem. 2019, 11, 80-85. [8] a) J. Tourneur, B. Fabre, G. Loget, et al. J. Am. Chem. Soc. 2019, 141, 11954. b) K. Oh, V. Dorcet, B. Fabre, G. Loget, Adv. Energy Mater. 2019, 1902963. Figure 1

Limitations and Benefits of MAX Phases in Electroanalysis

AbstractMAX phases are a group of layered 2D materials made of early transition metal, A‐group element (e.g., Al, Sn or Si), and C or N. These nanolaminated carbides and nitrides combine many attractive characteristics of metals and ceramics such as excellent electric and thermal conductivity and high chemical resistance. Although MAX phases have shown promising electrochemical results in the field of energy conversion, their use for electroanalytical approaches is nowadays an unexplored field. Herein, the potential use of MAX phases for electroanalytical approaches has been investigated. For this aim, seven different MAX phases (Cr2AlC, Mo2AlC, Ta2AlC, Ti2AlN, Ti2SnC, Ti3AlC2, Ti3SiC2, and V2AlC) have been drop‐casted upon a conventional glassy‐carbon electrode and tested at different pH media, also providing their potential towards the determination of different analytes. Overall, our findings elucidate the limitations and benefits of using MAX phases for electroanalysis, demonstrating that a proper combination of both MAX phases and electrolyte media is a must to direct efficient performances as electrode for electroanalysis. Accordingly, this work provides new knowledge about the electrochemical behaviour of MAX phases and their potential in the field of electronic devices.

Novel Lithium‐Sulfur Polymer Battery Operating at Moderate Temperature

AbstractA safe lithium‐sulfur (Li−S) battery employs a composite polymer electrolyte based on a poly(ethylene glycol) dimethyl ether (PEGDME) solid at room temperature. The electrolyte membrane enables a stable and reversible Li−S electrochemical process already at 50 °C, with low resistance at the electrode/electrolyte interphase and fast Li+ transport. The relatively low molecular weight of the PEGDME and the optimal membrane composition in terms of salts and ceramic allow a liquid‐like Li−S conversion reaction by heating at moderately high temperature, still holding the solid‐like polymer state of the cell. Therefore, the electrochemical reaction of the polymer Li−S cell is characterized by the typical dissolution of lithium polysulfides into the electrolyte medium during discharge and the subsequent deposition of sulfur at the electrode/electrolyte interphase during charge. On the other hand, the remarkable thermal stability of the composite polymer electrolyte (up to 300 °C) suggests a lithium‐metal battery with safety content significantly higher than that using the common, flammable liquid solutions. Hence, the Li−S polymer battery delivers at 50 °C and 2 V a stable capacity approaching 700 mAh gS−1, with a steady‐state coulombic efficiency of 98 %. These results suggest a novel, alternative approach to achieve safe, high‐energy batteries with solid polymer configuration.

Research developments in carbon materials based sensors for determination of hormones

Various carbon-based sensors (graphene, carbon nanotubes, graphite, pencil graphite, glassy carbon, etc.) have distinctive behavior and a broad range of importance for identifying sex hormones like estriol, estradiol, estrone, progesterone, and testosterone. The current review emphasizes voltammetric, amperometric, and electrochemical impedance spectroscopic methods for detecting some of these hormones. The existence, structural aspects, nature, and biological importance of each hormone were analyzed in detail and their analysis with different electroanalytical methods was considered. Unique methodologies and innovations of electrochemical sensors for hormones based on carbon materials modified by different agents were examined. In this review, the interaction among various sensor materials and analytes in different supporting electrolyte media is premeditated. The most important significances of the electroanalytical methodologies were discussed based on sensor selectivity, sensitivity, stability, the limit of detection, repeatability, and reproducibility.

Solvent dielectric effect on electrochemical properties of 3,4-propylenedioxythiophene

The present study is focused on the electrochemical properties of poly(3,4-propylene­dioxy­thiophene) (Poly(ProDOT)), electrocoated on the single carbon-fiber microelectrode (SCFME) in different electrolytic media, with different solvent dielectric constants (35.9, 41.7, 47.5, 53.3, 59.1 and 64.9). The highest deposition charge density of 24.49 mC cm-2 and the highest specific capacitance of 23.17 mF cm-2 were obtained for Poly(ProDOT) synthesized in a medium with the lowest solvent dielectric constant (e = 35.9). Electrochemical impedance spectroscopy (EIS) results of Poly(ProDOT) coated SCFME measured at open circuit potential showed continuously increased impedance magnitudes as ε was increased from 35.9 to 59.1. For all films, almost capacitive impedance responses at lower frequencies at least were obtained. The highest capacitance was observed for the polymer film synthesized in the medium of e = 35.9. The impedance of this film was also measured in different solvent mixtures with different dielectric constants at open circuit potential.

Copper-Catalyzed Electrosynthesis of Nitrite and Nitrate from Ammonia: Tuning the Selectivity via an Interplay Between Homogeneous and Heterogeneous Catalysis.

Electrocatalytic oxidation of ammonia is an appealing, low-temperature process for the sustainable production of nitrites and nitrates that avoids the formation of pernicious N2 O and can be fully powered by renewable electricity. Currently, however, the number of known efficient catalysts for such a reaction is limited. The present work demonstrates that copper-based electrodes exhibit high electrocatalytic activity and selectivity for the NH3 oxidation to NO2 - and NO3 - in alkaline solutions. Systematic investigation of the effects of pH and potential on the kinetics of the reaction using voltammetric analysis andin situ Raman spectroscopy suggest that ammonia electrooxidation on copper occurrs via two primary catalytic mechanisms. In the first pathway, NH3 is converted to NO2 - via a homogeneous electrocatalytic process mediated by redox transformations of aqueous [Cu(OH)4 ]-/2- species, which dissolve from the electrode. The second pathway is the heterogeneous catalytic oxidation of NH3 on the electrode surface favoring the formation of NO3 - . By virtue of its nature, the homogeneous-mediated pathway enables higher selectivity and was less affected by electrode poisoning with the strongly adsorbed "N" intermediates that have plagued the electrocatalytic ammonia oxidation field. Thus, the selectivity of the Cu-catalyzed NH3 oxidation towards either nitrite or nitrate can be achieved through balancing the kinetics of the two mechanisms by adjusting the pH of the electrolyte medium and potential.

THE INFLUENCE OF LEMON (Citrus Limon (L.)) IRON ION (Fe) REMOVAL ON STAINLESS STEEL ORTHODONTIC WIRE

Background: Lemons consist of 5-8% citric acid, have a pH of around 2.74. Drinks that have a critical pH of 5.5 can be said to be acidic drinks. Acidic drinks have the potential to cause corrosion of teeth and dental materials, one of which is stainless steel orthodontic wire. Stainless steel orthodontic wire is easily corroded, the wire has a composition of 71% Iron (Fe), 18% Chromium (Cr), 8% Nickel (Ni), and 0.2% Carbon (C). Corrosion is caused by the presence of inorganic components that act as electrolyte media that can trigger electrochemical reactions.Method: Each sample was placed on each uninsulated petridish and labeled as a marker. This is done by inserting orthodontic wire which is immersed into the incubator for 3.5 hours at 37℃. Then the sample is taken and the separation between the sample and the solution is carried out. After that, the measurement of Iron (Fe) ions was carried out using the Atomic Absorption Spectrophotomery tool.Result: The results showed the average release of Iron (Fe) ions in the experimental group of lemon juice with a concentration of 25% was 0.067mg/L, a concentration of 50% was 0.090mg/L and a concentration of 100% was 0.135mg/L. The test results obtained using the One Way Anova test showed that there was no significant difference (p>0.05).Conclusion: There was no significant difference in the release of Iron (Fe) ions in stainless steel orthodontic wires between experimental groups, and there was no effect of soaking lemon juice (Citrus Limon (L.)) on the release of Iron (Fe) ions in stainless steel orthodontic wires.

Interaction of crystal violet dye with dodecyltrimethylammonium bromide in aqueous and electrolyte medium at different temperatures

Dyeing is one of the most important processes in the textile industries which require optimum binding of dye with the fabrics. In the binding phenomenon of dye with the fabrics, surfactants play a significant role. The presence of different auxiliaries modifies the dye-surfactant interaction which can influence the binding of dye with the fabrics. Herein, we studied the interaction of crystal violet (CV) dye with a cationic surfactant, dodecyltrimethylammonium bromide (DTAB) conductometrically in absence and presence of electrolytes (NaBr, Na2SO4, and Na3PO4). The critical micelle concentration (cmc) of DTAB was found to dwindle with the boost of concentration of CV. The cmc of CV + DTAB mixtures were monotonically increased with the increase of temperature. The presence of electrolytes facilitates the micellization of CV + DTAB mixture. The values of counterion binding were found to be augmented with the augmentation of temperature in aqueous and NaBr media while the opposite trend was observed in Na2SO4 and Na3PO4 media. The Gibbs free energy of micellization (ΔGm0) were found to be negative in all cases. The enthalpy (ΔHm0) and entropy (ΔSm0) of micellization were negative and positive in aqueous, NaBr, and Na2SO4 media while both values were positive in Na3PO4 medium. The enthalpy–entropy compensation parameters suggest that the most stable micelle of CV + DTAB is formed in Na2SO4 medium.

Electrochemical properties of brownmillerite structured KBiFe2O5

In the present work, brownmillerite KBiFe2O5 (KBFO), a relatively new multifunctional compound, has been explored as an electrode material for applications in supercapacitors. Polycrystalline KBFO is synthesized via citrate combustion method. The phase formation, crystallinity, composition and morphology of KBFO samples are investigated using XRD, HRTEM, XPS and FESEM. As synthesized KBFO sample possesses rectangular rod-like morphology with monoclinic crystal system. The electrochemical properties of KBFO were analyzed using Galvanostatic charge/discharge (GCD), Cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) in acidic, alkaline and neutral electrolyte media. GCD results show a promising energy storage property with remarkable 100% capacitive retention after 1000 cycles. CV results also establish the pseudocapacitive nature of KBFO in all electrolyte media. These features support the feasibility of exploitation of KBFO for advanced energy storage applications.

The Future of Nuclear Energy: Electrochemical Reprocessing of Fuel Takes Center Stage

Nuclear power plants use energy-dense fuel and provide dependable baseload energy without generating greenhouse gas emissions. Despite these advantages, the long-term management of used nuclear fuel (UNF) remains a key challenge due to its lifetime (hundreds of thousands of years) and radiotoxicity. The components of UNF that contribute the most to this challenge are the actinide elements. A potential solution to this issue is to separate these radioisotopes from the bulk of the UNF and recycle them as fuel in advanced nuclear reactors. These separations can be achieved using electrochemical reprocessing, which employs electrochemical conversion and electrodeposition in a high-temperature molten salt electrolyte medium to separate the actinides from UNF. In this short perspective, we review the current status, fundamental challenges, and future prospects of electrochemical reprocessing as they relate to UNF recycling.

Design and development of defect rich titania nanostructure for efficient electrocatalyst for hydrogen evolution reaction in an acidic electrolyte

Cost-effective, efficient and stable electrocatalyst for water splitting in the acidic electrolyte medium has been developed. The acidic electrolyte could be a support for the high purity hydrogen production via water splitting. Accordingly, we have prepared the defect-rich titania nanostructure via electrochemical anodization and cathodization routes using the titanium plate, which showed highly effective and durable electrocatalyst of hydrogen evolution reaction (HER) in an acidic medium. This hybrid compound showed a low onset potential of −0.17 V for HER with a current density of −150 mA cm−2 in 1 M H2SO4. Moreover, the stability test has been performed with the defect-rich titania nanostructure as cathode for 6 h in the two electrodes system.

Enhanced hydrogen evolution reaction activity of FeM (M = Pt, Pd, Ru, Rh) nanoparticles with N-doped carbon coatings over a wide-pH environment

The alloy catalyst formed by transition metal and a small amount of noble metal has become the most promising substitute for M-based (M = Pt, Pd, Ru, Rh) catalyst. However, due to the direct exposure of the metal core to the electrolyte, it is vulnerable to corrosion and oxidation, which in turn reduces the catalytic stability and is becoming a major obstacle to sustainable hydrogen production. The present work addresses this issue by developing a one-step immersion-adsorption-pyrolysis strategy for synthesizing FeM alloy nanoparticles with N-doped carbon coatings ([email protected]) for use as electrocatalysts in the HER. The deliberately designed metal-organic framework material was used as the precursor of catalyst synthesis to achieve the carbon coatings and simultaneously the heteroatom in-situ doping for the alloy nanoparticles. The optimal [email protected] demonstrates excellent catalytic stability and HER activity in an acidic electrolyte medium. The reactions obtain a small overpotential of 28 mV to achieve current densities of 10 mA cm−2, which are comparable to a high-performance commercial Pt/C electrocatalyst with a much higher Pt loading. The [email protected] also demonstrates an outstanding performance with an overpotential of only 18 mV to achieve a current density of 10 mA cm−2 in an alkaline medium.

Studies on electrochemical mechanism of nanostructured cobalt vanadate electrode material for pseudocapacitors

The supercapacitive behaviour of chemically synthesized cobalt vanadate nanostructures was reported in this work. Various analytical techniques along with optical studies were utilized to investigate the crystallographic information's and optical response. Crystallographic information of the prepared nanostructures was revealed by the XRD analysis and it's formation was confirmed by the FTIR and XPS techniques. The nano-layered structural and surface morphology was observed through scanning electron microscopy and high-resolution transmission electron microscopy. Electrochemical performances in aqueous electrolytic medium were examined for supercapacitive behaviour of prepared Co3V2O8. Specific capacitance value of about 790 F/g was achieved at 1 A/g current density and the superior capacitive retention of 90.1 % after 10000 cycles had been imparted by the prepared Co3V2O8. Based on the results, it was confirmed that the prepared cobalt vanadate nanostructures can be used as an electrode material for future energy storage devices.

Oxidation kinetics and behaviour of Pb – Zn alloy anodes

Lead and its alloys are widely used in hydroelectric metallurgy, in the production of chemical power sources, electroplating, as well as in electrochemical methods of corrosion protection. To increase the resistance and reduce the anodic potential of lead-based electrodes, various methods are used which allow to solve new problems in industrial electrolysis. Currently, the main task is the creation of new anode alloys, which will allow for the optimal selection of the anode for each specific case. In this regard, lead and its alloys in the foreseeable future will remain the main material in the electrolysis production. Taking into account the operation of lead alloys at high temperatures and corrosive environments, the kinetics of oxidation of alloys of the Pb – Zn system containing up to 0.5 wt% zinc was investigated by thermogravimetry. It has been found that the addive of zinc to lead increases its resistance to oxidation in the solid state. It is shown that the oxidation of alloys occurs according to a hyperbolic mechanism and has the order of 10–4 kg·m–2·s–1. The anodic behavior of the alloys in the NaCl electrolyte medium was studied by the potentiostatic method at a potential sweep rate of 2 mV/s. It was found that zinc as an alloying component does not significantly improve the corrosion resistance of lead. In this case, with an increase in the additive of zinc to lead, the main electrochemical potentials (corrosion, pitting formation, and repassivation) of the alloys will mix in the field of positive values. With an increase of the concentration of chloride ion in the NaCl electrolyte, the corrosion rate of alloys increases, while the values of electrochemical potentials decrease.

MWCNT incorporated wool-ball-like CuO@NiO hybrid nanostructures for high-performance energy storage device

In the present work, some CuO@NiO@MWCNT (CNC) ternary hybrid nanostructures have been synthesized solvothermally in a well-controlled manner by varying the amount of MWCNT for energy storage application with superior electrochemical performance. Among three CNC1 (CuO@NiO:40 mg MWCNT), CNC2 (CuO@NiO:40 mg MWCNT; in one-step method) and CNC3 (CuO@NiO:60 mg MWCNT) nanocomposites, the CNC1 has emerged out with the best performance due to its well-designed components and synergistic effects, wool ball-like morphology and a mesoporous structure containing more active sites, a shortest conductive pathway for electron-ion transportation. The CNC1 hybrid with a highly ordered mesoporous structure (pore radius ~1.9 nm) offers a high specific surface area of 262 m2 g−1. The structure and microstructure of these ternary hybrid nanocomposites are characterized by analyzing respective X-ray diffraction patterns, HRTEM, FESEM images, and XPS spectra. HRTEM and FESEM images reveal the uniform distribution of the MWCNT network and the growth of spherical NiO nanoparticles of 8–10 nm in these CNT. The optimized ternary wool ball-like CNC1sample exhibits a high specific capacitance of 786 F g−1 and high areal capacitance of 3.144 F cm−2at a current density of 0.6 A g−1 with a significant rate capability. A two-electrode asymmetric device has been designed with the CNC1 sample as the positive electrode and activated carbon as the negative electrode in a 1 M Na2SO4 electrolyte medium. This device offers maximum specific energy of 32.21 Wh Kg−1, a maximum power density of 3923 W Kg−1, excellent cyclic stability and a high Coulomb efficiency. The optimum use of MWCNT in CNC1 ternary nanostructures results in better morphology, leading to a significant reduction in charge transfer parameters,as revealed by EIS spectroscopy.

Conductivity and cloud point studies of the interaction of lomefloxacin hydrochloride with anionic and nonionic surfactants in electrolytes solution

The interaction of lomefloxacin hydrochloride (LMFH) drug (utilized to treat different bacterial infections) with anionic (sodium dodecyl sulfate (SDS)) and nonionic (triton X-100 (TX-100)) surfactants in electrolytes media has been carried out applying the conductometric and cloud point (CP) measurement methods. SDS is very useful to prohibit different viral infections and to extract DNA/RNA. Two critical micelle concentrations (cmc) were observed for LMFH + SDS mixtures within the investigated surfactant concentration. The cmc values of SDS increase monotonically with the increase of the LMFH concentration. The cmc values of LMFH + SDS mixtures were reduced as the ionic strength of electrolytes increases. In the case of the LMFH + SDS mixture, the cmc values showed reverse U-shaped change with the augmentation of temperature in the electrolyte medium. The extent of counterion binding (β) varies significantly with the change of ionic strength of the electrolytes and concentration of the drug. The CP values of the LMFH + TX-100 mixture was increased and decreased with the enhancing of LMFH and electrolyte concentrations respectively. The standard Gibbs free energy changes both for first and second micellization (ΔG1,mo &ΔG2,mo) were attained to be negative throughout the study suggesting spontaneous micellization of LMFH + SDS mixture in all the cases. The ΔG1,mo &ΔG2,mo values increase with the increase of temperature. Again, ΔG2,mo > ΔG1,mo signify that second micellization is more spontaneous. The positive free energy changes of the LMFH + TX-100 mixture reveal the nonspontaneous nature of the clouding process. The non-spontaneity of clouding experiences a reduction with the rise of TX-100 concentration. The other thermodynamic parameters, transfer properties as well as entropy-enthalpy compensation parameters of micellization and clouding processes have been assessed. The intrinsic enthalpy (ΔHmo,∗) values reveal that micelle is more stable in electrolyte media.