Papers by Keyword: Cyclic Voltammetry

Abstract: Treatment of graphene/SiC dies in inorganic electrolytes (KOH, KCl and Na₂SO₄) is discussed. An electrochemical method based on the cyclic voltammetry in a conventional three-electrode cell with Ag/AgCl reference electrode, a platinum counter electrode, and the graphene/SiC dies as working electrode (anode) is used for the treatment. It was observed either partial oxidation of graphene or its complete dissolution with the formation of CO₂. The treatment performed resulted in the deterioration of the graphene films and change of the graphene-die resistivity depending on the range of the scanning potential applied to the graphene/SiC dies.

Abstract: This paper on optimizing the anodised Al oxide for DNA detection by using Taguchi method. One step anodizing is carry out in the mixture electrolyte using phosphoric and oxalic acid. Control factor for this study is voltage, concentration and time. The corrosion tested to measure polarization resistance. The Taguchi methods will be optimize the anodizing parameter for DNA application. These three samples is then undergo DNA immobilization with 10µM DNA with amine-terminated group and leave it in 4h at RT. The cyclic voltammetry used to detect DNA by measure the immobilization current (Iimmo). From the result, anodized part with DNA immobilized have higher immobilized current thanpolarized part with DNA. Scanning Electron Microscope (SEM) is to observe the surface morphology of the anodized and polarize part. The result show anodized part had more particle and dispersed around than the polarize part.

Abstract: A simple method has been developed to prepare carbon nanotube/graphite/zinc oxide (CNT/GT/ZnO) composite on SS foil substrate which was employed for supercapacitor electrode materials. The XRD study reveals the formation of CNT/GT/ZnO structure. Scanning electron microscopy characterizations reveal that the combination of CNT/GT and ZnO can increase the conductive property of material. The electrochemical performance of composite electrode was investigated using cyclic voltammetry measurements in 1 M KCl aqueous electrolyte. The CNT/GT/ZnO composite electrode shows the specific capacitance up to 6.99 Fg⁻¹ in scan rate of 25 mVs^-1 with an energy density of 152.9 Wh kg⁻¹ in the potential range −0.5 V to 0.5 V.

Abstract: Orderly TiO₂ nanotube arrays (TNTs) with high surface area became a prospective catalyst support. TNTs were obtained by anodizing Ti plate, and then the Ni-Cu-B/TNTs electrodes were prepared by cyclic voltammetry electrodeposition (CVE) method. SEM, EDS and electrochemical testing were used to investigate the microstructure and catalytic performance Ni-Cu-B/TNTs electrodes for methanol electro-oxidation. Effects of electrodeposition time, CVE scanning rate and times on the methanol electrooxidation were studied. The results show the shape of Ni-Cu-B particles on surface change from fusiform-like to spherical with an increasing of deposition temperature. The peak current density initially increased and then decreased with increasing electrodeposition time, rate and number of CVE scanning. The Ni-Cu-B/ TNTs electrode prepared by 30 cyclic times in 30°C at-0.8~0.2V and the scan rate of 20mV s^-1 appear the best electrocatalytic activity for methanol oxidation. After cycled 1300 times for methanol oxidation, the peak current density decreased by 12%, indicating excellent long term stability of Ni-Cu-B/TNTs electrode.

Abstract: It was established that the silver nanoparticles (AgNPs) in an equimolar ratio have the highest electrochemical activity on a graphite electrode (GE) surface in an alkaline medium. The electrocatalytic oxidation mechanism of hydrogen peroxide on the GE surface was proposed. We detected an additional maximum at E = 0.3 V on the cathodic branch of the cyclic curve in the potential range from +2.0 to -1.0 V. The appearance of this maximum indicates the reduction of hydrogen peroxide generated during AgNPs electrooxidation in the potential range from -1.0 to +2.0 V.

Abstract: The stepwise mechanism of electrooxidation and reduction of silver nanophases and microphases is proposed on the graphite electrodes surface in alkaline medium. The electrochemical splitting of silver nanophases peak is observed on the anodic branch of the cyclic current-voltage curve. There is the shoulder at E = 0.2 V on the he anodic branch of cyclic current-voltage curve. The appearance of additional cathodic wave at E = -0.08 V is observed on the cathodic branch of the cyclic current-voltage curve that is caused by the reduction of silver nanoparticles. The additional cathode maximum is represented at 0.3 V on the cathodic branch of the cylic current-voltage curves of only silver nanophases. This effect is associated the catalytic process of decomposition of hydrogen peroxide on silver nanoparticles surface. The offset of the cathodic maxima of current-voltage curves of silver nanophases obtained with an excess of a reducing agent are observed to more negative potentials. There is a significant decrease of the all currents maxima compared to silver nanophases obtained with an equal molar ratio of reactants. These results may be connected with the formation of silver oxide monolayers in the different oxidation in the presence of large amounts a reducing agent. The excess of the reducing agent required for the preparation of silver nanoparticles leads to decrease of the cathodic maximum of silver nanoparticles

Abstract: The pitting corrosion behavior of AISI 202 stainless steel (SS) – a low-nickel, austenitic SS grade, was investigated by means of cyclic voltammetry (CV) technique complemented by Scanning Electron Microscopy (SEM). From the starting potential, the current density decreases and changes its sign at the corrosion potential (Ecorr). The anodic response exhibits a well-defined anodic peak followed by a passive region. A noticeable increase in the anodic current density was observed after reaching the breakdown potential (Eb). The second anodic peak which may be attributed to onset of oxygen evolution was also observed. Moreover, the cyclic voltammograms revealed that hysteresis loop is absent for all the studied concentrations, indicating that AISI 202 SS in citric acid is highly resistant to pitting corrosion as also supported by the results of SEM. It was found out that the critical current density (icrit) increases with increasing citric acid concentration.

Abstract: The paper discusses the electrochemical interactions of Co-Cr alloy with different physiological solutions and organic substances, containing different ions and different pH values, which should play a key role in the materials lifetime. The physical and chemical reactions are numerous and the passivity of the Co-Cr alloy is submitted to the influence of the liquid environment. Some electrochemical investigations were carried out for understanding and predicting the passivity and the corrosion resistance of Co-Cr alloy in three types of simulated body fluids (SBF), namely Fusayama Meyer artificial saliva (pH=5), Hank’s solution (pH=7.4), Ringer's solution (pH=6.6) and citric acid as organic solution. The reason of using another type of environment (other than SBF), such as citric acid is that this medium is a powerful oxidant and has a lower pH value (pH=1.8). This acid environment can influence the state (the formation and growth) of the oxide layer on the surface of the alloy. Research has shown different behavior of the cobalt chromium alloy according to the pH, the chloride content and the oxidizing nature of the environment. Co-Cr alloy biomaterial, immersed in four aqueous media reveals that there are different levels of stabilization of the potential and different current densities depending on the pH value. The Co-Cr alloy biomaterial is very sensitive to localized corrosion (pitting) in Hank solution.

Abstract: Effect of glucose loading on the synthesis mesoporous carbon had been studied using hard template method where mesoporous silica SBA-15 was used as a template. To obtain a large pore of mesoporous carbon sample, a large pore of silica template was used. A series of mesoporous carbon sample was synthesized by loading different amounts of glucose (2.5g, 5.0g and 10.0g) as a carbon precursor to ensure that the template was fully impregnated with precursor. After treatment process, the surface area of carbon samples were measured with Brunauer-Emmett-Teller (BET) analysis and it shows that higher amount of glucose gives higher surface area due to the large pore of the template used. The samples then were tested with cyclic voltammetry technique at different scan rates (10, 20, 30 and 50 mVs^-1) in 6M KOH electrolyte. It reveals that higher surface area samples show a higher specific capacitance with 119 F/g at slow scan rate 10 mVs^-1.

Abstract: The “inverse” cathodic peak of gold nanoparticles is observed in the reaction mixture used to obtain gold nanoparticles HAuCl₄:Na₃C₆H₅O₇:NaBH₄=125:8:1 and accumulation time is 90 s. The conditions in which methionine has the greatest electrochemical activity were determined. They are as follows: the molar ratio of reagents HAuCl₄:Na₃C₆H₅O₇:NaBH₄=125:8:1 and accumulation time is 90 s, 0.1 M NaOH. The mechanism of methionine oxidation is proposed to be on the surface of the graphite electrode modified with gold nanoparticles in 0.1 M NaOH. The determination limit of methionine is 0.7 •10^-14 M. The proposed method is simple, sensitive, and does not need toxic substances.