Papers by Keyword: Cyclic Voltammetry

Abstract: This research was conducted to study changes in functional groups after oxidation of porous carbon synthesized from palm kernel shell and their effects on the performance of material for an electric double-layer capacitor (EDLC). Porous carbon was prepared by pyrolysis of palm kernel shell at a temperature of 800 °C and steam activation. Surface modification was conducted by oxidation porous carbon using hydrogen peroxide (H₂O₂). Properties of material were characterized using N₂-sorption analysis, scanning electron microscopy (SEM), and Fourier transforms infrared spectroscopy (FTIR) analysis. Measurement of biomass-based porous carbon as an electrode for EDLC was carried out using cyclic voltammetry and galvanostatic charge-discharge methods. The test was conducted using a three-electrode system, with carbon as the working electrode, Ag/AgCl as the reference electrode, Pt as the auxiliary electrode. The electrolyte used was 1 M H₂SO₄ solution. The results showed that oxidation of porous carbon using H₂O₂ lowers the specific surface area but increases oxygen functional groups in the carbon surface. The results on testing the performance of EDLC, surface-modified carbon showed better EDLC performance of 5-7 times higher compared to carbon before oxidation.

Abstract: Cyclic voltammetry is a widely used technique in electrochemistry due to its simplicity and large amount of data and information that can be obtained. This study utilises this technique to study chlorophyll a and total chlorophyll (Tchl) alongside a laser light to induce photosynthesis. No oxidative peak was observed, regardless of the solution pH in either a dark or light environment when using a solution with an electrolyte of tetrabutylammonium perchlorate (TBAP) in both dichloromethane (DCM) and acetonitrile (MeCN), whereas in a solution of aqueous HCl a small anodic peak was observed. The concentration of the droplet of Tchl pigment on the surface of macro glassy carbon electrode (GCE) was increased, which resulted in a similar trend and the oxidation peak was observed to be slightly larger when in the presence of light. It was observed that the filtered solution of Tchl pigment produced a weaker signal than the unfiltered solution and there were slightly reduced oxidative peak currents when the concentration of VK₁ was increased. were no observed changes in the peak charges or currents over a wide potential range (0.0, 0.2, 0.4, 0.6 and 0.8 V) in the presence or absence of light by using coulometry and amperometry methods, therefore, more information on the 3-D formation is required for the photoreduction processes.

Abstract: This study aims to investigate the feasibility of modifying graphite electrode with zero-valent iron (ZVI) to electrochemically detect the presence of 3-MCPD using two (2) deposition methods, namely dip coating and drop casting. Both methods were tested against in situ and ex situ ZVI formation method. Results showed that ex situ ZVI formation using drop casting method onto graphite electrode showed highest peak current when tested using cyclic voltammetry (CV). Results also showed that the 3-MCPD presence was detected at potential range of-25 mV to 45 mV due to the sudden spike in electrical current when tested using CV mode. The impact of this study is to provide a basis for further investigation of 3-MCPD detection in palm oil using electrochemical method due to its simplicity for the development of a portable, fast and reliable 3-MCPD sensor.

Abstract: Supercapacitor is an electronic device with characteristic of having higher power density than battery and higher energy density than conventional capacitor. In order to achieve exceptional power and energy density, it is necessary to use materials with high specific surface area as its electrodes. In this study, we prepared a rolled supercapacitor device model using carbon sheet as the electrodes and 1 M KCl electrolyte. A carbon sheet was soaked in 1 M KCl and assembled as a rolled supercapacitor device model. Performance of the rolled supercapacitor device model was measured using a cyclic voltammetry (CV) in a voltage range of-0.8 V to +0.1 V with scan rate variations of 1 mV/s, 5 mV/s, 10 mV/s, 15 mV/s and 20 mV/s. Cyclic voltammetry measurement provide results as follows, E_sp = 0.289 to 0.103 Wh/kg and P_sp = 5.024 to 35.738 W/kg. By using Ragone plot we found that the prepared rolled supercapacitor using carbon-sheet as electrodes had met criteria of supercapacitor. The result show that the carbon sheet has a good prospect to be used as electrodes for rolled supercapacitor.

Abstract: Cyclic voltammetry can be used to investigate the chemical reactivity of species ion via oxidation and reduction process. The purpose of this study is to determine the level energy of high occupied molecule orbital (HOMO) and low unoccupied molecule orbital (LUMO) in polythiophene (PT), Poly (3-thiophene acetic acid) (P3TAA), polypyrrole (PPY) and chlorophyll (Chlo) through oxidation and reduction of molecular ions by cyclic voltammetry method. PT, P3TAA, PPY and Chlo solutions were prepared in a solvent of acetonitrile at the concentration range of 10^-2 to 10^-4 M. The current-voltage measurements for these solutions are performed using cyclic voltammetry method on input voltage from -2.0 V to 2.0 V. The working electrode used is indium tin oxide (ITO). The result of voltammogram is showed that the activity of PT species were produced three oxidation and one reduction processes. The formal reduction potential, E^o_¢ is 0.83 (positive) meaning that oxidation process was dominant. So that the reaction of PT species was exhibited irreversible electrochemical behavior. The reaction of P3TAA species was exhibited reversible electrochemical behavior, where the range value of oxidation, DE_pa and reduction, DE_pc were in range of 0.825 V to 1.120 V and -0.230 V to 0.131 V respectively. PYY species reaction was exhibited irreversible electrochemical behavior where two oxidation states occur within -0.145 V to -0.202 V and 0.870 V to 1.63 V respectively. The species activity of Chlo was exhibited irreversible electrochemical behavior where only the oxidation process was obviously appeared at range of 0.80 V to 0.95 V. The LUMO energy levels of PT, P3TAA PPY and Chlo were 5.84 eV, 5.34 eV, 1.10 eV and 3.85 eV respectively, while HOMO energy levels of PT, P3TAA PPY and Chlo were 4.61 eV, 4.25eV, 3.70 eV and 5.93 eV. The average value of energy gap of PT, P3TAA, PPY and Chlo were 1.23 eV, 1.08 eV, 2.23 eV and 1.10 eV respectively.

Abstract: Prussian Blue Like (PBL) compounds that are potentially used as K-Ion Battery (KIB) electrodes have been synthesized from zinc(II) chloride and quinoline (Qn) precursors combining melting and direct reaction method. The formed K₂[Zn(Qn)₂][Co(SCN)₆] compounds melt in range 179-181°C with conductivity value reaches 468 μS/cm. Thiocyanate and quinoline ligands were characterized using FT-IR and UV-Vis spectrometry. The cyclic voltammetry of the formed compounds showed the reduction potential up to -0.34 V (versus AgCl/Ag).

Abstract: The adsorption behavior and inhibition mechanism of (1, 4, 7-Tris [hydrogen (6-methylpyridin-2-yl) phosphonate] -1, 4, 7-triazacyclononane) (TPP) on the corrosion of mild steel in 1 M HCl were investigated by weight loss technique, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods for different concentrations at 25°C. The results show that the inhibition efficiency values depend on the amount of immersion times and the concentration. A 90% efficiency is found at the highest concentration of the studied compound according to weight loss measurements. The adsorption of the investigated inhibitor on the mild steel surface was well supported using an AFM study. For the assignment of the absorption sites, we performed quantum chemical calculations with (DFT) method. The interaction between the inhibitor and iron surface were performed by molecular dynamic (MD) simulations. In this paper, experimental methods and results used to assess the efficiency of the studied compound are presented.

Abstract: Electrolytes in supercapacitors (SCs) play an important role on their energy storage capacity. The electrochemical stability of electrolytes defines the operating potential of the SCs and their viscosity defines a power density of the SCs. In the present work, a new method for composing an electrochemically stabile but high viscous ethylene glycol (EG) based electrolyte has been discussed. A viscosity of the EG then reduced by dissolving an inorganic lithium tetrafluoroborate (LiBF₄) salt. The affect of the concentration of the salt on EG viscosity has been investigated. The best capacitive performance of activated carbon (AC) based electrodes with large operating potential (-1.7V to 1.7V) was found in 3M LiBF₄/EG electrolyte.

Abstract: Graphene oxide (GO) layer has been successfully deposited on to ITO/TiO₂ substrate by electrochemical deposition. Deposition process of GO layers were carried out in one, three, and six cycles in the voltage range of-1.6 to 0 volt and scan rate of 50 mV/s. The variation of cycles was performed, in order to study the deposition process relates to device performances. TiO₂ macro-channel (TiO₂μc) also introduced in photoanode system and it required annealing treatment up to 500°C. The oxygen content in GO will be reduced by annealing treatment and the reduced-GO (rGO) layer was trapped inside of TiO₂ mesoporous. The cyclic voltammetry curves of blank sample and GO deposition were also observed in order to ensure the GO deposition process was successfully done. After immersing in ruthenium dye overnight, the ITO/TiO₂/rGO/TiO₂-μc was sandwiched with Pt/FTO as counter electrode to configure dye sensitized solar cell (DSSC) structure. The photovoltaic characteristics, morphology, and UV-Vis absorbance of each layer were investigated. A highest DSSC efficiency (η= 3.34 %) was achieved by 3-cycles of GO deposition process of photoanode with photocurrent density (J_sc) of 9.94 mA/cm², open voltage (V_oc) of 0.70 V and fill factor (FF) of 48.69% under 100 mW/cm² of light irradiation.

Abstract: Corncobs are a waste product from corn farming that are abundant in Indonesia. Corncobs have a high cellulose content, more than 40%, which made it useful for synthesizing CMC. CMC is a cellulose derivative that is widely used in many industries such as food, pharmaceutical, detergent, textile, cosmetic product and binder. In this paper, we use CMC that are synthesized from corncobs as binder in the electrodes of lithium ion battery. The steps of synthesizing CMC from corncobs started with the isolation of the cellulose, then followed by the processes of alkalization, carboxymethylation and finally the purification. FTIR spectrum shows that CMC are successfully synthesized. The presence of strong absorption band at 1613 cm^-1 is related to the stretching vibration of the carboxyl group (COO-). The absorption in the 1300–1450 cm^-1 region is due to symmetrical deformations of CH₂ groups. While the broad absorption around 3427 cm^-1 is due to the stretching of the hydroxyl groups (-OH). Test on three samples of different sizes, (mesh-100, mesh-60 and mesh-40) gives CMC purity values of 98.69%, 98.56% and 97.77%, respectively. In the application of CMC as anode binder, the best composition is 4% CMC, where it gives the highest conductivity of 0.587 S/cm. Voltammogram measurement with a scan rate of 50 mV/s in the voltage range of -1 to 1 Volt gives the capacitance value of 2237 μF.