Cyclic Voltammetric Studies Research Articles

PHYSICOCHEMICAL AND SPECTROSCOPIC ANALYSIS OF INTERACTIONS BETWEEN ASPIRIN AND NORMAL SALINE AT DIFFERENT TEMPERATURES

The primary goal of the current investigation is to explore the molecular interactions between the aspirin (2-Acetoxybenzoic acid) and normal saline (0.9% w/v aqueous NaCl) at various concentrations (0.001–0.010) m and temperature (T= 300.15–315.15) K. To understand the various possible molecular interactions, volumetric, acoustic, conductometric and viscometric parameters were evaluated using experimental measured values of densities (ρ), ultrasonic velocities (u), specific conductance (κ), and viscosities (η). The results derived from these parameters have been examined in terms of drug–solvent and drug-drug interactions. The results of physicochemical studies indicate that aspirin exhibits strong interactional and structure–forming behaviour in normal saline. These results were well supported by UV-visible spectral studies which indicate the existence of intense aspirin–normal saline interactions in the form of modification in absorption maximum and absorption wavelength. The cyclic voltammetric studies were also performed to explore the oxidation/reduction behaviour and effect of aspirin on hemolysis. The experimental analysis of these studies provides valuable insights for better drug design, drug delivery, compatibility, potential safety, and biological relevance for the pharmaceutical and health industries.

Electrochemical, photocatalytic and biological investigation of carbaldehyde derived azo dye ligand and its Co(II), Ni(II), Cu(II) complexes

2-[(E)-(3-hydroxypyridin-2-yl)diazenyl]-1H-indole-3-carbaldehyde (HDC) a novel azo dye ligand and its Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) complexes have been prepared. The newly synthesized compounds were characterized by physiochemical techniques. The modified electrode, [Co(HDC)2Cl2]/GCE has been prepared by using the synthesized Co(Ⅱ) complex to check the electrocatalytic properties by cyclic Voltammetric (CV) studies. The biologically important molecule, folic acid present in the solution at different concentration has been detected by CV technique. The sensitivity of [Co(HDC)2Cl2]/GCE was 8.366 μAμM−1cm−2 and the limit of detection (LOD) 6.666 μM/L in the linear range 20–140 μM/L. The oxidation current of folic acid increased potentially with scan rate and the regression found was 0.9961, which indicates surface diffusion-controlled nature of process. The synthesized compounds were also screened for antimicrobial, antioxidant and anticancer activities. All the synthesized compounds gave promising results towards biological activities. The photodegradation of Methylene Blue dye was studied under visible light and in the presence of metal complexes to determine the catalytic efficiency of the synthesized metal complexes. The results indicated that the [Co(HDC)2Cl2] exhibited excellent results when compared to [Ni(HDC)2Cl2] and [Cu(HDC)2Cl2] complexes.

Selective Chromogenic Chemosensors for Arsenite Anion: A Facile Approach to Analyzing Arsenite in Honey, Milk, and Water Samples.

In this study, two chemosensors, N5R1 and N5R2, based on 5-(4-nitrophenyl)-2-furaldehyde, with varying electron-withdrawing groups, were synthesized and effectively employed for the colorimetric selective detection of arsenite anions in a DMSO/H2O solvent mixture (8 : 2, v/v). Chemosensors N5R1 and N5R2 exhibited a distinct color change upon binding with arsenite, accompanied by a spectral shift toward the near-infrared region (Δλmax exceeding 200 nm). These chemosensors established stability between a pH range 6-12. Among them, N5R2 displayed the lowest detection limit of 17.63 ppb with a high binding constant of 2.6163×105 M-1 for arsenite. The binding mechanism involved initial hydrogen bonding between the NH binding site and the arsenite anion, followed by deprotonation and an intramolecular charge transfer (ICT) mechanism. The mechanism was confirmed through UV and 1H NMR titrations, cyclic voltammetric studies, and theoretical calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Real water samples, honey, and milk samples were successfully analyzed by both chemosensors for the sensing of arsenite.

Exploring Spectral and Electrochemical Behavior of Hydroxy‐N‐Benzylideneanilines by Integrated Theoretical and Experimental Approaches

ABSTRACTThe present work explored the effect of –OH group substitution (o/p) on the spectral and electrochemical behavior of N‐benzylideneaniline. The geometry optimization of unsubstituted and (o/p)‐OH‐substituted analogs revealed the coplanarity of the molecules. The vibrational spectra of the compounds were computed using density functional theory (DFT) and compared with the experimental data. The observed bands were assigned based on total energy distribution (TED). Predicted electronic absorption spectra from time‐dependent density functional theory (TD‐DFT) calculation were compared with the UV–visible spectra of the molecules. The analysis of the lowest spin‐allowed (singlet‐singlet) excited states divulged possible electronic transition. The o‐substituted benzylideneaniline possessed the lowest highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap among the substituted and unsubstituted analogs. The intramolecular contacts were interpreted using natural bond orbital and localized molecular orbital analysis. The –CH=N– linkage was investigated as a bridge for the electron delocalization from the donor to acceptor moieties. The manifestation of a reduction peak in the cyclic voltammetric studies confirmed the electrochemical behavior in the –OH‐substituted molecule, which was diffusion‐controlled. The discrepancy in the electrochemical property concerning the position of the –OH substituent of the candidate molecules was put forward.

Hardness, VSM, cyclic voltammetric and DFT studies of Cesium Sulphate-doped TGS crystals

The creation of capacitors, transducers, sensors, and infrared detectors utilise the nonlinear, ferroelectric triglycine sulphate (TGS) crystal. Cesium sulphate is incorporated into the lattice of TGS crystal to change its characteristics. Cesium sulfate-doped triglycine sulphate (CSTGS) single crystals were produced using a solution approach and a slow evaporation process. The title crystal was studied by single crystal XRD, FTIR, hardness, VSM, cyclic voltammetric and density functional theoretical (DFT) studies and the results are discussed in this paper.

Ion Transport Through Nanopores and the Effects of Pore Wall-Ion Interaction.

Ion transport inside nanopores is affected by the physicochemical interactions between the ions and the internal pore wall, offering novel opportunities useful for nanopore-based applications. Here we demonstrate that the transport of Fe(CN)63-/4- is influenced by the pore wall-ion interactions in sub-10 nm pore channels of a mesoporous zirconia film (MZF) formed on an electrode based on cyclic voltammetric (CV) studies. At pH lower than the point of zero charge of zirconia, the pore wall is positively charged, enabling it to exert attractive interaction with the negatively charged analyte ions. Moreover, experimental data indicate that the attractive interaction strongly favors the more highly charged Fe(CN)64- ions over the Fe(CN)63- ions. These effects affect the ion transport through the MZF nanopore channels, which is manifested by a number of different sets of data, including the positive shift of the reduction potential, the disparity between the CV curves of the anodic and cathodic sweeps, and the splitting of the single pair of redox peaks into two pairs when the electrical double layer thickness is increased by reducing the concentration of the supporting electrolyte. Each of these observations can be explained by the wall-ion interactions. Our findings may lead to further explorations into the transport of redox ions that interact differently with the pores and into the development of novel applications based on nanopores.

Electrosynthesis of 1,2,3-Benzotriazines through an Iodide-Catalyzed Skeletal Editing of 3-Aminoindazoles.

This report describes an environmentally benign synthesis of 1,2,3-benzotriazines through an iodide-catalyzed electro-oxidative N-centered [1,2]-rearrangement of 3-aminoindazoles. The developed method demonstrates the activation of heteroatoms via electrochemically generated reactive iodide species without using any metal catalysts and peroxides. The protocol features practical and mild reaction conditions and displays a wide substrate scope. Various mechanistic experiments and cyclic voltammetric studies have been instrumental in elucidating the reaction mechanism, operating via a skeletal rearrangement of 3-aminoindazoles.

Fabrication of nanomolecular platform based immunosensor for non-invasive electrochemical detection of oral cancer: An in vitro study

Silver nanoparticles (AgNPs)-Chitosan (Chi) functionalized cysteine (cys)-SAM (self-assembled monolayer) based electrochemical, label free, ultrasensitive, non-invasive immunosensing nanomolecular platform has been fabricated for the detection of novel OC biomarker S-100. This has been achieved through bio-functionalization of AgNPs-Chi/cys/mini gold slides by covalent immobilization of anti-S100 antibodies. Cyclic voltammetric (CV) studies establish successful fabrication of anti-S100/AgNPs-Chi/Au nanomolecular platform. Differential pulse voltammetric (DPV) measurements reveal that anti-S100/Chi-AgNPs/Au is able to sense 50 fg mL-1 – 500 ng mL-1 of S100 in buffer and in spiked saliva samples within 120 s interaction time having improved favorable shelf life and specificity. The fabricated platform is very selective and able to detect S100 in OC patient/s saliva samples warrants realization of simple non-invasive electrochemical immunosensor for in situ or on-site applications (especially for remote areas) for early diagnosis of OC while offering bio-compatibility at low cost.

Synthesis and Characterization of Carbon Nano Sphere-doped Gd: Alpha Sb2O4 Nanostructure for High-Performance Energy Storage Applications

Background: To enhance the super capacitive properties of nanocomposites, the effective method is to combine carbon nanospheres with mesoporous structures with Gd3+:α-Sb2O4 inorganic nanocomposites (NC) to form hybrid electrodes. An as-prepared hybrid electrode material possesses increased energy density, high rate of reversibility and cyclic stability when incorporated in electrochemical cyclic voltammetric studies. Methods: In the present investigation, various wt % of C-nanospheres (Cx) (5 %, 10% and 20%) were decorated over Gd3+: α-Sb2O4 nanocomposites and were synthesized by coprecipitation method. XRD, SEM, EDX, UV-visible, and XPS are only a few of the analytical techniques used to describe the as-prepared hybrid nanocomposites. Electrochemical cyclic voltammetry was carried out in a 6 M KOH solution, three-electrode system. Results: The crystal structure and morphology of Cx: Gd3+@ α-Sb2O4 NC showed a mixed hexagonal phase and agglomerated tiny irregularly shaped morphology that appeared as the Cx concentration increased. Redshift in optical absorption peak appeared (near UV-edge), and the optical band gap (Eg) value increased from 3.53 eV to 3.65 eV. The electrochemical supercapacitor showed the highest specific capacitance of 989 F/g at the current density of 1 A/g for C20%:Gd3+@α-Sb2O4 NC compared with Cx:Gd3+@α-Sb2O4 (x = 5% and 10%) and undoped Gd3+:α-Sb2O4 NC. The change in phase angle and Rs value of 1.98 was attributed to the ideal supercapacitor properties. The cyclic stability after 5000 cycles with 79.71% capacitive retention was exhibited by C20%:Gd3+@α-Sb2O4 NC. Conclusion: The present research introduces ease of synthesis of hybrid electrode materials possessing high active surface area, increased energy density, high cyclic stability, and reversibility in an aqueous solution.

Enhanced favipiravir drug degradation using the synergy of PbO2-based anodic oxidation and Fe-MOF-based cathodic electro-Fenton

Favipiravir (FAV) is a widely utilized antiviral drug effective against various viruses, including SARS-CoV-2, influenza, and RNA viruses. This article aims to introduce a novel approach, known as Linear-Paired Electrocatalytic Degradation (LPED), as an efficient technique for the electrocatalytic degradation of emerging pollutants. LPED involves simultaneously utilizing a carbon-Felt/Co-PbO2 anode and a carbon-felt/Co/Fe-MOF-74 cathode, working together to degrade and mineralize FAV. The prepared anode and cathode characteristics were analyzed using XPS, SEM, EDX mapping, XRD, LSV, and CV analyses. A rotatable central composite design-based quadratic model was employed to optimize FAV degradation, yielding statistically desirable results. Under optimized conditions (pH = 5, current density = 4.2 mA/cm2, FAV concentration = 0.4 mM), individual processes of cathodic electro-Fenton and anodic oxidation with a CF/Co-PbO2 anode achieved degradation rates of 58.9% and 89.5% after 120 min, respectively. In contrast, using the LPED strategy resulted in a remarkable degradation efficiency of 98.4%. Furthermore, a cyclic voltammetric study of FAV on a glassy carbon electrode was conducted to gather additional electrochemical insights and rectify previously published data regarding redox behavior, pH-dependent properties, and adsorption activities. The research also offers a new understanding of the LPED mechanism of FAV at the surfaces of both CF/Co-PbO2 and CF/Co/Fe-MOF-74 electrodes, utilizing data from cyclic voltammetry and LC-MS techniques. The conceptual strategy of LPED is generalizable in order to the synergism of anodic oxidation and cathodic electro-Fenton for the degradation of other toxic and resistant pollutants.

Photocatalytic and electrochemical investigation of Mn and Sn co-doped ZnO nanoparticles: Effect of doping concentration

The chemical precipitation method is employed to prepare the Mn and Sn co-doped ZnO nanoparticles with various doping concentrations. Debye Scherrer’s formula, Williamson-Hall equation and Halder-Wagner methods are used to calculate the crystallite size of the prepared nanoparticles. The addition of dopants enhances the periodicity of the atoms. The bond lengths, second nearest neighbor distances and bond angles are examined. The purity of the samples is confirmed using energy dispersive X-ray analysis technique. The process of doping reduces the maximum optical absorption. The dopants reduce the band gap of the prepared nanoparticles and the band gap ranges from 3.07 eV to 3.03 eV. The charge carrier concentrations are calculated from the optical band gap. The Hall coefficient of the prepared nanoparticles increases due to the addition of the dopants. The refractive index of the material is also examined. The quenching is observed in the photoluminescence spectrum due to the dopants. The dielectric properties and electric modulus depend on doping concentrations of Mn and Sn. The degradation of the Congo red and methylene blue dyes with prepared nanoparticles as catalysis is reported. The specific charge of the Mn and Sn co-doped ZnO-based electrode is analyzed using cyclic voltammetric study and galvanostatic charge–discharge technique.

Electrochemical sensing of nitrate ions at Cu-immobilized gold electrode in neutral medium

The Cu-immobilized Au surface was electro-catalytically employed for nitrate ions reduction in a neutral solution. According to cyclic voltammetric studies, the Cu/Au electrode has an improved electro-catalytic impact on converting nitrate ions into nitrite ions, governed by a two-electron transfer system. This modified electrode demonstrated good performance in real sample analysis along with good sensitivity (3.2518 $ \mu A \mu M^{-1} cm^{-2}$), long linear detection range (1.2 to 111.4 $\mu M$), a very lower limit of detection (0.85 $\mu M$), an excellent reproducibility. Thus, to determine nitrate ions in an aqueous media, an electrochemical sensor based on a Cu/Au electrode is suggested. GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 10(1), 2023 P 75-85

CVD based synthesis of binder free nanostructured MgS/MoS2@NiF electrode material for asymmetric supercapacitor applications

Two-dimensional molybdenum disulfide (MoS2) electrode materials (EMs) have gained significant interest due to their remarkable electrochemical performance in renewable energy storage devices (RESDs). However, the layered agglomeration decreases the EMs practical applications in RESDs. By combining with transition metal sulfide, layered agglomeration and electrochemical performance can be improved violently. Therefore, in this research work, MoS2-based magnesium sulfide (MgS/MoS2) nanostructured EMs are synthesized on nickel foam (NiF) via a chemical-vapor-deposition (CVD) technique. The synthesis of MoS2 and heterostructured MgS/MoS2@NiF EMs having cluster of nanoparticles and nanoneedles like microstructure is confirmed by field emission scanning electron microscopic analysis. The surface area (170 m2g-1) of nanoneedles based MgS/MoS2@NiF EMs is significantly higher than the surface area (60 m2g-1) of nanoparticles based MoS2@NiF EMs, causes to increase the electrocheomical performance of the syntehsized EMs. The MgS/MoS2@NiF EMs is preserved maximum specific capacitance of 9149 Fg-1 at 10 Ag-1, energy density of 234–171 Whkg-1, power density of 2150–4300 Wkg-1 and capacitance retention of 98.2 % for 10,000 cycles. The cyclic voltammetric study is indicated that the EMs have pseudocapacitive nature (diffusion process) which is increased by addition of MgS layer over MoS2 surface. The shifting of impedance profile to y-axis confirmed the increasing diffusion rate of ions in the pores of MoS2 by the addition of MgS layer. The theoretical Dunn's model also revealed that the over-all current produced by the synthesized EMs is due to the current contribution of diffusive and capacitive controlled process. The asymmetric supercapacitor (ASC) device preserved pseudocapacitive nature with maximum specific capacitance of 701 Fg-1 at 4 Ag-1. Moreover, the ASC device is presented the energy density ranged from 288 to 151 Whkg-1, power density ranged from 3440 to 21,500 Wkg-1, Coulombic efficiency of 100 % and capacitance retention of 95 % for 10,000 cycles performed at 20 Ag-1.

Synthesis of sulphone-infused two-dimensional microporous covalent organic frameworks involving Ni(II) porphyrin and sulfur powder for the photocatalytic generation of N-benzylidene benzylamine and their derivatives

In this article, the synthesis of a two-dimensional sulfone-based microporous COF, Ni-P has been executed via C-S coupling of nickel (II) tetra(p-bromophenyl) porphyrin with sulfur powder in the presence of the catalytic amount of CuI and benzotriazole in an inert atmosphere (N2) at 120 °C for 7–8 hrs. The authenticity as well as physiochemical properties of the compound have been investigated using FT-IR, XPS, XRD, TGA, SEM, and BET. The optical band gap (1.9 eV) and electrochemical band gap (2.1 eV) of Ni-P have been calculated through UV–vis and cyclic voltammetric study which finds Ni-P a suitable candidate for photocatalytic study. In the chemical transformation reactions, Ni-P shows an excellent conversion rate of benzylamine for the generation of N-benzylidene benzylamine through oxidative coupling (yield ∼ 99 %). In the photostability study, even after 5 times, it shows good recyclability as evidenced by FT-IR and XRD data.

Novel Hybrid Copper-Based Electrode for Non-Enzymatic Electrochemical Lactic Acid Sensing in Milk Samples

A novel developed non-enzymatic electrochemical sensor was designed for the detection of lactic acid (LA) in perishable products, with a focus on monitoring milk spoilage. The sensor utilizes a hybrid copper-based electrode consisting of cuprous oxide (Cu2O), copper oxide (CuO), and copper hydroxide (Cu(OH)2), which collectively contribute to enhanced performance through their synergistic effects. Cyclic voltammetric studies revealed distinct oxidation peaks associated with LA detection, highlighting the superior catalytic effect of the Cu2O/CuO/Cu(OH)2 electrode compared to CuO alone. Further optimization of the metal loading on the electrode surface led to improve LA sensing properties. The sensor exhibited a wide linear response range (0.25–7 mM), high sensitivity (817.66 μA·mM−1·cm−2), and a low limit of detection (0.25 mM). Selectivity tests indicated negligible interference from common dairy product constituents, while stability tests showed consistent performance over a 3 week storage period (100% stability). The practical usability of the sensor was demonstrated through the quantitative analysis of LA in pasteurized milk, with recovery values ranging from 99.7% to 106.9%, confirming the feasibility of the sensor for real sample analysis. The developed multiphase copper-based electrode presents a promising platform for the sensitive and reliable detection of LA within the dairy industry.

Enhancing the energy storage performance of titanium dioxide electrode material by green doping of Nd2O3 nanoparticles for electrochemical supercapacitors

Doping of sesquioxide alloy onto TiO2 nanomaterials was carried out in a novel green chemistry method using Corallo carpus epigaeus to fabricate the electrodes for pseudocapacitors. The conducted X-ray diffraction studies demonstrated the tetragonal phase of TiO2 and hexagonal phase of Nd2O3 nanomaterials. Morphological analysis revealed the irregular shape of TiO2 materials, each exceeding 100 nm in size, while Nd2O3 materials exhibited a spherical shape within the range of 10–20 nm. Electrochemical investigations unveiled a quasi-rectangular shape in cyclic voltammetric studies and a triangular shape in galvanostatic reactions, suggesting superior electrochemical performance of the electrodes. The doped electrodes exhibited a higher specific capacitance value (785.71 F/g) compared to pure TiO2 (707.14 F/g) at a current density of 1 A/g. These findings affirm the suitability of doped electrode materials for applications in electrical energy storage.

Design and synthesis of heteroleptic Ni(II) dipyrrin complexes for electrochemical proton reduction reactions: Cyclic voltammetric and theoretical studies

The effect of nuclearity on electrochemical hydrogen generation using new heteroleptic Ni(II) complexes containing redox-active dipyrrin and dithiocarbamate ligands has been described. Complexes 1–2 have been meticulously characterized by spectroscopic studies (ESI-MS, IR, 1H, 13C NMR, UV–vis) and their structures unambiguously confirmed by X-ray single crystal analyses. Electrocatalytic properties of the complexes toward hydrogen evolution reaction have been investigated by cyclic voltammetric studies in an organic medium in the presence of acetic acid as a weak proton source. Notably, complexes 1 and 2 produce H2 via doubly reduced Ni(II) species i.e. Ni(0) in the presence of acetic acid. Further, these complexes exhibited significant electrocatalytic activity (TOF: 264 (1) and 650 s−1 (2). Controlled potential electrolysis established a minimum Faradaic efficiency of 92 (1) and 96 % (2). Complex 2 exhibited higher turnover frequency relative to 1, while 1 showed lower overpotential (0.35 V) in comparison to 2 (0.45 V). The stability of the complexes and the amount of produced H2 has been investigated by bulk electrolysis study. A tentative mechanism (ECEC; E, electrons and C, chemical steps) and involved intermediate species for the proton reduction reaction for 1 has been established by theoretical studies.

Redox behaviour of boron subphthalocyanine carbon nanotube composites

Organic redox-active carbon composites can be used as sustainable electrode materials in electrochemical energy storage systems. Among numerous redox active species, peripherally dodecafluorinated boron subphthalocyanines (F12BsubPcs) have shown electrochemical redox activities in the solution phase. Nonetheless, the electrochemical properties of solid F12BsubPcs when compositing with nano carbon warrants further investigation for potential applications in energy storage. In this work, nanometer scale axially brominated F12BsubPcs (Br-F12BsubPcs) were coated onto bare graphitized multiwalled carbon nanotubes (GCNT) and COOH-functionalized GCNT (COOH-GCNT) by a facile dip coating method to produce two composites and to compare the effects of the surface functional group interactions with Br-F12BsubPcs. While the surface chemical and morphological characterizations confirmed the presence of Br-F12BsubPc coating on both bare and COOH-GCNTs, the coverage on the latter was higher. Cyclic voltammetric studies in acidic electrolyte revealed a highly reversible redox couple on both composites with Br-F12BsubPc coated COOH-GCNT demonstrating up to c.a. 70% higher redox peak currents than with Br-F12BsubPc coated GCNT. Further analyses of the coated COOH-GCNT suggested a 2-electron transfer process. The charge transfer has fast-kinetics and a strong dependence on the proton concentration. The composites produced in this work demonstrate potential for future application in energy storage and can provide a strategy for developing BsubPc-based carbon composites.

Surface Structure to Tailor the Electrochemical Behavior of Mixed-Valence Copper Sulfides during Water Electrolysis.

The semiconducting behavior of mixed-valence copper sulfides arises from the pronounced covalency of Cu-S bonds and the exchange coupling between CuI and CuII centers. Although electrocatalytic study with digenite Cu9S5 and covellite CuS has been performed earlier, detailed redox chemistry and its interpretation through lattice structure analysis have never been realized. Herein, nanostructured Cu9S5 and CuS are prepared and used as electrode materials to study their electrochemistry. Powder X-ray diffraction (PXRD) and microscopic studies have found the exposed surface of Cu9S5 to be d(0015) and d(002) for CuS. Tetrahedral (Td) CuII, distorted octahedral (Oh) CuII, and trigonal planar (Tp) CuI sites form the d(0015) surface of Cu9S5, while the (002) surface of CuS consists of only Td CuII. The distribution of CuI and CuII sites in the lattice, predicted by PXRD, can further be validated through core-level Cu 2p X-ray photoelectron spectroscopy (XPS). The difference in the electrochemical response of Cu9S5 and CuS arises predominantly from the different copper sites present in the exposed surfaces and their redox states. In situ Raman spectra recorded during cyclic voltammetric study indicates that Cu9S5 is more electrochemically labile compared to CuS and transforms rapidly to CuO/Cu2O. Contact-angle and BET analyses imply that a high-surface-energy and macroporous Cu9S5 surface favors the electrolyte diffusion, which leads to a pronounced redox response. Post-chronoamperometric (CA) characterizations identify the potential-dependent structural transformation of Cu9S5 and CuS to CuO/Cu2O/Cu(OH)2 electroactive species. The performance of the in situ formed copper-oxides towards electrocatalytic water-splitting is superior compared to the pristine copper sulfides. In this study, the redox chemistry of the Cu9S5/CuS has been correlated to the atomic arrangements and coordination geometry of the surface exposed sites. The structure-activity correlation provides in-depth knowledge of how to interpret the electrochemistry of metal sulfides and their in situ potential-driven surface/bulk transformation pathway to evolve the active phase.

(Invited) Effect of Carbonaceous Materials on the Performance of Supercapacitors

Carbonaceous materials such as carbon blacks, activated carbons, multi walled/single walled carbon nanotubes (CNTs), graphene oxide (GO), reduced graphene oxide (rGO), and biochar are found to be useful for energy storage applications because of their large specific surface area, high conductivity, high mechanical strength, good thermal stability, and low cost.In order to optimize the concentration of MWCNT in MnO2/MWCNT nanocomposite, we have synthesized MnO2/MWCNT nanocomposite with varying concentration of MWCNT such as pure MnO2, 1mg/ml, 4 mg/ml, and 10 mg/ml MWCNT in reaction mixture. The samples were identified as MnO2, M-CNT 100, M-CNT 400, and M-CNT 1000. From cyclic voltammetric studies at various scan rate, we plotted a graph between peak current () versus the scanning rate () and found that the slope of anodic (cathodic) peak for MnO2, M-CNT 100, M-CNT 400, and M-CNT 1000 were found to be 0.48 (0.42), 0.70 (0.61), 0.60 (0.54), and 0.52 (0.47), respectively. We also found that at a current density of 0.5 A/g, pure MnO2 has a specific capacitance of 124 F/g. The addition of MWCNT initially increases the specific capacitance to 145 F/g for M-CNT 100 nanocomposite; however, at the 400-mg and 1000-mg concentrations the specific capacitance decreases to 135 F/g and 102 F/g, respectively.Besides this, we have also studied the effect of binder on capacitive performance of MnO2/CuS/rGO samples and found that the specific capacitance of the composite materials increased upon decreasing the binder. The detailed results of our recent investigations on carbonaceous materials for supercapacitor applications will be presented at 244th ECS meeting.