Potential Cycling Technique Research Articles

Analysis of a Gel-like State of Nickel Hydroxide Created By Electrochemical Aging

As global energy demands increase, the need for clean energy and energy storage is evident. Water electrolysis has shown promise as a clean energy storage solution and can be coupled with other clean energy techniques (e.g., wind, solar) to store chemical energy in the form of hydrogen. Alkaline systems are of particular interest as they are more cost effective compared to acidic systems that require precious metal-based catalysts. Alkaline water electrolysis suffers from inefficiencies that include the oxidative half reaction known as the oxygen evolution reaction (OER). Nickel-based electrocatalysts are being developed for the electrochemical transformations of organic species and used in gas evolution reactions, such as the OER. Nickel-based materials are sought after in part for their lower cost relative to precious metal catalysts (e.g., Pt, Ru, Ir), but they lack the higher electrochemical activity achieved by their precious metal counterparts. To develop more active and durable materials and to better understand the mechanisms involved in electrochemical transformations on nickel-based materials, it is essential to understand how these materials evolve and age as a result of electrocatalytic use.In this study, we have preserved the hydrated form of Ni electrocatalysts aged under alkaline conditions relevant to the OER. We prepared a series of electrocatalysts with nano- and micro-scale grains that were polished to a similar nano-scale roughness. First, we electrochemically aged Ni electrocatalysts with nanoscale and microscale grains by potential cycling techniques (i.e., cyclic voltammetry). Following electrochemical aging, the Ni electrocatalysts were preserved by immersion in liquid nitrogen and sublimed in a lyophilizer. After this freeze-drying process, the electrocatalysts were imaged under cryogenic conditions using scanning electron microscopy (SEM) techniques. A comparison was made to aged electrocatalysts where freeze-drying was implemented and those that were allowed to air dry. The surfaces of aged Ni electrocatalysts were all observed to contain an electrochemically active layer with a gel-like form. When the catalysts were air-dried, the layer appeared to have a collapsed, web-like texture. Through the use of transmission electron microscopy analyses, it was determined that these gel-like layers contained predominantly nanocrystalline β-phase nickel hydroxide (β-Ni(OH)2), which likely formed due to relaxation of the OER active beta-phase nickel oxyhydroxide [β-NiOOH] prior to the imaging process. The formation of the gel-like layer covering these electrocatalysts has implications for dynamic processes taking place at their interface with the electrolyte. Processes influenced by the gel-like form of this active layer include the rates of diffusion of electrolyte, the mechanism of O2 bubble nucleation, and the mechanics of bubble release. The results of these studies also have implications for the electrocatalytic activity and stability of other types of electrocatalysts. Further, this work can be extended for the design of new electrocatalysts for a variety of electrocatalytic processes, such as the hydrogen evolution reaction and other gas evolution reactions. Figure 1

Adsorption of Copper Ions onto Poly(1,8‐diaminonaphthalene)/Graphene Film for Voltammetric Determination of Pyridoxine

AbstractIn this work, pyridoxine (vitamin B6) was determined by the square wave voltammetry at copper‐poly(1,8‐diaminonaphthalene)/graphene modified glassy carbon electrode. The composite electrodes were fabricated with two steps. First, poly(1,8‐diaminonaphthalene) is electrodeposited onto graphene/glassy carbon electrodes with a potential cycling technique. Then, copper ions are adsorbed onto the poly(1,8‐diaminonaphthalene)/graphene modified glassy carbon electrode due to the immersion of the polymeric modified electrode in an aqueous copper (II) solution. The characterizations of synthesized materials have shown the role of graphene in facilitating the electron transfer and the remarkably electrocatalytic ability of copper for pyridoxine oxidation on the electrode surface. In 0.1 M phosphate buffer solution (pH 7.4), the peak current of square wave voltammograms of pyridoxine increased linearly with their concentration in the ranges between 0.58 and 24.51 μM with the limit of detection of 0.3 μM. The proposed electrodes showed excellent reproducibility and stability.

Effect of Microscopic Oxygen Bubbles on Measured OER Catalyst Stability - a Comparative Study between RDE and MEA Measurements

Fast screening of OER catalysts for their intrinsic activity and stability is pivotal for the development of PEM electrolyzers.1 With respect to OER activity, catalyst screening is very well-established using different measurement techniques such as rotating disk electrode (RDE), flow-channel methods, or full cell measurements in an electrolyzer, where comparable activities are obtained. On the other hand, accelerated stability testing of OER catalysts has been reported to result in different stability lifetimes based on the testing method. For example, stability tests using the RDE technique result in magnificently shorter catalyst lifetimes than those using an electrolyzer.2 We have recently discovered that the use of an RDE-based galvanostatic test is not reliable to investigate the OER catalyst stability as the “apparent” catalyst degradation associated with this test is mostly due to a measurement artefact.3 During the OER galvanostatic test, oxygen gas bubbles form and accumulate in the pores of the catalyst layer, shielding the active surface area of the catalyst, therefore resulting in an increasing potential, mistakenly interpreted in the literature as catalyst degradation.4, 5 In this contribution, we present a comprehensive study in which we demonstrate how the accumulation of microscopic oxygen bubbles in the pores of the electrocatalyst layer during the OER results in an artefact that falsifies the estimated catalyst lifetime. We will show that this artefact exists in all RDE-based stability tests including galvanostatic, potentiostatic, and potential cycling techniques. Furthermore, we will show that the same artefact also exists during the stability test carried out using a membrane electrode assembly (MEA) in an electrolyzer, but to a much lesser extent compared to that associated with the RDE technique. We will also discuss how to mitigate this accumulation of gas bubbles in an MEA, and discuss possible protocols that enable the OER catalyst stability testing using RDE-based techniques. References L. Wang, F. Song, G. Ozouf, D. Geiger, T. Morawietz, M. Handl, P. Gazdzicki, C. Beauger, U. Kaiser, R. Hiesgen, A. S. Gago and K. A. Friedrich, J. Mater. Chem. A, 5(7), 3172–3178 (2017).S. Cherevko, Current Opinion in Electrochemistry, 8, 118–125 (2018).Hany A. El-Sayed, Alexandra Weiß, Lorenz F. Olbrich, Garin P. Putro, and Hubert A. Gasteiger, Journal of the Electrochemical Society, 166(8), F1-F7 (2019).H.-S. Oh, H. N. Nong, T. Reier, M. Gliech and P. Strasser, Chem. Sci., 6(6), 3321–3328 (2015).H.-S. Oh, H. N. Nong, T. Reier, A. Bergmann, M. Gliech, J. Ferreira de Araújo, E. Willinger, R. Schlögl, D. Teschner and P. Strasser, J. Am. Chem. Soc., 138(38), 12552–12563 (2016).

Synthesis and characterization of a novel non-enzymatic glucose biosensor based on polyaniline/zinc oxide/multi-walled carbon nanotube ternary nanocomposite

Novel polyaniline/zinc oxide/multi-walled carbon nanotube (PANI/ZnO/MWCNT) ternary nanocomposite was fabricated as a non-enzymatic glucose biosensor. Thermal chemical vapor deposition (CVD) process was employed to synthesize vertically aligned MWCNTs on stainless steel substrates coated by Co catalyst nanoparticles. In order to fabricate sensitive and reliable MWCNT-based biosensors, nanotubes density and alignment were adjusted by varying the CVD reaction time and cobalt sulfate concentration. The fabricated nanotubes were modified by ZnO particles through the potentiostatic electrodeposition technique. Optimal electrodeposition potential, electrodeposition time, and electrolyte concentration values were determined. The optimized ZnO/MWCNT nanocomposite was reinforced by polyaniline (PANI) nanofibers through the potential cycling technique, and the morphology, elemental composition, and phase structure of the fabricated nanocomposites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), respectively. The sensing mechanism of the PANI/ZnO/MWCNT electrode for the electrochemical detection of glucose was investigated, and the limit of detection and sensitivity values of the designed sensor were determined. The fast response time of the ternary nanocomposite-based sensor as well as its satisfactory stability and reproducibility, makes it a promising candidate for non-enzymatic detection of glucose in biomedical, environmental, and industrial applications.

EDTA_PANI/SWCNTs nanocomposite modified electrode for electrochemical determination of copper (II), lead (II) and mercury (II) ions

Present investigation deals with electrochemical determination of copper(II), lead(II) and mercury(II) ions, using ethylenediaminetetraacetic acid (EDTA) chelating ligand modified polyaniline (PANI) and singe walled carbon nanotubes (SWCNTs) based nanocomposite (PANI/SWNCTs). Stainless steel (SS) electrode was modified with PANI and SWCNTs based nanocomposite. PANI/SWCNTs nanocomposite was electrochemically synthesized using potential cycling technique. Further it was modified with EDTA in the presence of 1-ethyl-3(3-(dimethylamin propyl)carbodiimide (EDC) as activating agent, using dip coating technique at room temperature. The EDTA_PANI/SWCNTs/SS electrode was characterized by cyclic voltammetry in 0.5 M H2SO4, which was complemented with electrochemical impedance spectroscopy (EIS). AFM and SEM analysis was applied for the morphological studies of EDTA_PANI/SWCNTs nanocomposite structure. FTIR analysis was applied for the structural and compositional analysis of EDTA_PANI/SWCNTs nanocomposite. All the characterizations were performed before and after the modification of PANI/SWCNTs nanocomposite structure with chelating ligand. Differential pulse voltammetry (DPV) was used for the determination of Cu(II), Pb(II) and Hg(II) ion concentrations. Analytical characteristic such as selectivity and sensitivity of here above-mentioned metal ions was studied. The limit of detection the EDTA_PANI/SWCNTs/SS toward Cu(II), Pb(II) and Hg(II) was determined as 0.08 μM, 1.65 μM and 0.68 μM respectively.

Amperometric glucose sensor based on the Ni(OH)2/Al(OH)4− electrode obtained from a thin Ni3Al foil

In this report, we present a facile and relatively fast method to roughen the surface of Ni3Al–based intermetallic foil, and test it as an amperometric non-enzymatic glucose sensor. The alloy samples underwent chemical etching in a H3PO4:CH3COOH (HAc):HNO3:H2O (24:1:1:7 in volume) solution in order to achieve a high surface area with more electroactive sites. The Ni(OH)2/Al(OH)4− electrode was fabricated using potential cycling technique in a highly concentrated alkaline solution. The electrodes were tested electrochemically for oxidation of glucose. We have demonstrated that Ni(OH)2/Al(OH)4− electrodes exhibit high sensitivity towards glucose detection (796μAmM-1cm-2) and short response time (3s) upon successive addition of glucose. Moreover, as for a non-nanometric material, prepared electrodes show a relatively good linear correlation between current density and glucose concentration (0.025–0.45mM) and limit of detection (47.6μM). For more in-depth characterization of presented material, electrodes were examined using scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).

In situ synthesis of Ni(OH)2/TiO2 composite film on NiTi alloy for non-enzymatic glucose sensing

A one-step potential cycling technique for in situ synthesis of electroactive Ni(OH)2 and protective TiO2 composite film on NiTi alloy is described. The Ni(OH)2/TiO2 composite film can be used directly as the electrode in a non-enzymatic glucose sensor. This binder-free sensor boasts a high glucose sensitivity of 192μAmM−1cm−2, short response time of less than 1s, and detection limit of 8μM. In addition, the stable and protective TiO2 extends the linear range to 14mM and provides excellent long-term stability. This novel fabrication method not only simplifies the preparation of high-performance non-enzymatic glucose sensing materials, but also can be readily extended to the fabrication of other transition metal-based biosensors.

Electrocatalytic Oxidation of Methanol on Glassy Carbon Electrode Modified by Metal Ions (Copper and Nickel) Dispersed into Polyaniline Film

Polyaniline film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of glassy carbon electrode. Then transition metal ions of Ni and Cu were incorporated to the polymer by immersion of the modified electrode. A comparative study of the electrocatalytic oxidation of methanol is made in NaOH, on Ni and Cu on polyaniline film covered glassy carbon electrode (Ni-PANI-GC, Cu-PANI-GC) at 25℃. Catalytic activity for the oxidation of methanol was studied by using cyclic voltammetry.

Iron(III) oxide adsorbed multiwalled carbon nanotube modified glassy carbon electrode as a precursor for enhanced Prussian blue formation and selective hydrogen peroxide sensing

Prussian blue (PB), an inorganic iron-hexacyanoferrate polymer, is a potential redox system. In general, it can be prepared on any conducting substrate by electrochemical deposition technique in which a working electrode is potential cycled with millimolar quantities of a mixture FeCl3 and [Fe(CN)6]3− in an alkaline metal ion containing acid solution (pH<3). Here in we report preparation of a new hybrid PB by a template assisted preparation method, where rather to taking any mixture, the [Fe(CN)6]3− is subjected to the electrochemical potential cycling technique with a Iron(III) adsorbed multiwalled carbon nanotube modified glassy carbon electrode (GCE/MWCNT–Fe2O3), as a template, in pH 2 KCl–HCl. The PB electrode thus designated as GCE/MWCNT–Fe2O3@PB showed well-defined redox peaks at apparent standard electrode potentials, 190±5 and 850±5mV vs Ag/AgCl and synergistic effect of PB, MWCNT and Fe2O3 systems. As prepared MWCNT–Fe2O3@PB was characterized by various physico-chemical techniques such as Scanning electron microscopy, Energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. Presence of trace amount of the precursor, Fe2O3 within the inner core of the hybrid PB system was evident from the characterization results. In further, it was found that one of the metallic impurities, iron in the MWCNT has influenced the PB formation. The new hybrid PB electrode exhibited 17 times higher reduction current value over the conventionally prepared GCE/PB for the H2O2 electrocatalysis. Applicability of the electrode to sensing of H2O2 in real sample such as milk, cream bleach and clinical solution was successfully demonstrated.

Voltammetric simultaneous determination of glucose, ascorbic acid and dopamine on glassy carbon electrode modified byNiNPs@poly 1,5-diaminonaphthalene

A simple and effective strategy was proposed for synthesis of nickel nanoparticls dispersed at poly1,5-diaminonaphthalene(NiNPs@P-1,5-DAN). NiNPs@P-1,5-DAN was prepared by using repeated potential cycling technique in an acidic solution containing 1.5mM 1,5-diaminonaphthalene at glassy carbon electrode surface, giving the GC modified electrode (P-1,5-DAN/GC). The transition metal ions of Ni(Π) were incorporated to the polymer by immersion of the modified electrode in a 1.0M nickel chloride solution, NiNPs@P-1,5-DAN modified electrode was obtained and characterized by scanning electron microscope (SEM). The electrochemical characterization of this modified electrode exhibits stable redox behavior of Ni(III)/Ni(II) couple in 0.1M NaOH aqueous solution. The electrooxidation of single glucose (Glu), ascorbic acid (AA) and dopamine (DA) in 0.1M NaOH was studied by using square wave voltammetry (SWV). NiNPs@P-1,5-DAN/GC modified electrode was applied for the electrocatalytic oxidation and simultaneous determination of Glu, AA and DA in alkaline solution. The calibration curves for Glu, AA and DA were plotted. The detection limits were 0.252, 0.010 and 0.011μM for Glu, AA and DA respectively.

Electrochemical studies of Pt/Ir–IrO 2 electrocatalyst as a bifunctional oxygen electrode

In the present study, Ir nanoparticles are deposited on the surface of IrO 2 nanoparticles with microwave-assisted polyol process. Then the obtained Ir–IrO 2 nanocomposite is used as a support to prepare Pt/Ir–IrO 2 nanocomposite, which has been demonstrated as an excellent bifunctional oxygen catalyst for unitized regenerative fuel cell. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and transmission electron microscopy (TEM) characterizations indicate that ultrafine Ir nanoparticles (NPs) are uniformly dispersed on the surface of IrO 2, which provides a conductive network for Pt NPs. Electrocatalytic activity and stability of Pt/Ir–IrO 2 are investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potential cycling techniques on rotating disc electrode (RDE). Results show that the electrocatalytic activity of Pt/Ir–IrO 2 towards oxygen reduction reaction (ORR) is much higher than that of Pt/IrO 2, and the electrocatalytic activity of Pt/Ir–IrO 2 towards oxygen evolution reaction (OER) can be comparable to that of Pt/IrO 2. Life tests reveal that Pt/Ir–IrO 2 exhibits excellent stability. The enhanced ORR activity of Pt/Ir–IrO 2 catalyst can be attributed to the improvement in electronic conductivity, and its higher stability can be assigned to the special structure, in which the interaction between Pt NPs and Ir NPs prevents Pt from agglomerating.

Electrodeposition and Characterization of Thin-Film Platinum-Iridium Alloys for Biological Interfaces

An efficient platinum-iridium thin film alloy electrodeposition method has been evaluated to modify the surface of platinum or gold microelectrodes that are being developed for neural recording and stimulation applications. A large number of electrodeposition process variables have been investigated in terms of how they affected the properties of the electrodeposited films. Three sets of Pt-Ir films of a certain composition were electroplated on gold substrates using a potential cycling technique and characterized using microscopy, elemental analysis, nanoindentation, and electrochemical techniques to evaluate the repeatability of the electrodeposition process. Deposition rates were estimated by determining film mass and thickness as a function of deposition time. The surface morphology of the Pt-Ir films was characterized using scanning electron microscopy (SEM) and the chemical composition was determined using wavelength dispersive spectroscopy (WDS). Nanoindentation measurements showed that the hardness of the electroplated Pt-Ir thin films was nearly 100% higher than that of a Pt foil. The electrochemical properties of the films were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and compared with those of pure Pt, pure Ir and 80–20% Pt-Ir foils. The final electroplating process resulted in 60–40% Pt-Ir alloys. The film thickness increased with electrodeposition time at a rate of 16.5 nm/min and stable films with up to 500 nm thickness were obtained. Characterization by SEM and EIS revealed that the real surface area of the Pt-Ir films was much larger than that of pure Pt and increased significantly with increasing deposition time.

Anodic TiO2 nanotube layers electrochemically filled with MoO3 and their antimicrobial properties

In the present work, the authors produce a Ti surface with a TiO₂ nanotube coating and investigate the electrochemical filling of these layers with MoO₃. The authors demonstrate that using a potential cycling technique, a homogenous MoO₃ coating can be generated. Controllable and variable coating thicknesses are achieved by a variation of the number of cycles. Thicknesses from a few nanometers to complete filling of the nanotube layers can be obtained. A thermal treatment is used to convert the as-deposited amorphous MoO(x) phases into MoO₃. These MoO₃ loaded nanotube layers were then investigated regarding their antimicrobial properties using strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The authors found that the combination of crystalline MoO₃ on TiO₂ nanotubes shows excellent antimicrobial properties.

Influence of Surface Pretreatment of MWNTs Support on PEFC Performance

The influence of surface characteristics of multi-walled carbon nanotubes (MWNTs) support on the catalytic performance of PEFC electrodes is investigated by using oxidized and non-oxidized MWNTs as the supports for platinum. The defect-free morphology, high electrical conductivity and favorable pore-size distribution of non-oxidized MWNTs ameliorate catalytic activity and electrochemical stability of platinum. Physico-chemical properties of oxidized and non-oxidized MWNTs and the respective catalysts are studied by BET surface-area, XRD, XPS and TEM measurements. Electrochemical stability of MWNTs-supported platinum as PEFC electrodes is assessed using potential cycling and potentiostatic techniques. Owing to the higher corrosion-resistance, platinum on non-oxidized MWNTs show lower loss in electrochemical surface area (ESA) and also exhibit 22% lower corrosion current than oxidized MWNTs.

Performance of glucose electrooxidation on Ni–Co composition dispersed on the poly(isonicotinic acid) (SDS) film

Poly(isonicotinic acid) (PINA) film was electrosynthesized on carbon paste electrode (CPE) by using the repeated potential cycling technique in aqueous solution containing isonicotinic acid (INA), sulfuric acid and sodium dodecyl sulfate (SDS). Then, nickel and cobalt ions were incorporated by immersion of CPE/PINA prepared in the presence of SDS (CPE/PINA(SDS)) in a solution with different proportions of nickel chloride and cobalt chloride. The electrochemical characterization of mixed hydroxides containing cobalt and nickel at the surface of the modified electrode is presented. The modified electrodes were successfully used in the electrocatalytic oxidation of glucose. Finally, the electrocatalytic oxidation peak currents of glucose exhibited a good linear dependence on concentration, and its quantification can be done easily. The good analytical performance, low cost and straightforward preparation method make this novel electrode material promising for the development of an effective glucose sensor.

Electrocatalytic Oxidation of Hydrogen Peroxide on Poly(m‐toluidine)‐Nickel Modified Carbon Paste Electrode in Alkaline Medium

AbstractThe poly(m‐toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO4, also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m‐toluidine)/modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 μM (S/N=3). The catalytic reaction rate constant, (kh), was calculated 5.5×102 M−1 s−1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.

Carbon paste electrode modified by cobalt ions dispersed into poly (N-methylaniline) preparing in the presence of SDS: application in electrocatalytic oxidation of hydrogen peroxide

Conducting and stable poly (N-methylaniline) film was prepared by using the repeated potential cycling technique in aqueous solution containing N-methylaniline, sulfuric acid, and sodium dodecyl sulfate (SDS) at the surface of carbon paste electrode (CPE). The transition metal ions of Co(ІІ) were incorporated to the polymer by immersion of the modified electrode in 0.1 M cobalt chloride solution for 10 min. The electrochemical characterization of this modified electrode exhibits stable redox behavior of Co(ІІ)→Co(ІІІ) and formation of insoluble oxide/hydroxide cobalt species on the CPE surface. The modified electrode showed well-defined and stable redox couples in alkaline aqueous solution. The modified electrode showed excellent electrocatalytic activity for oxidation of hydrogen peroxide. The response of modified electrode toward the H2O2 oxidation was examined using cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, and chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility, and high catalytic activity toward the hydrogen peroxide oxidation. Such characteristics were explored for the specific determination of hydrogen peroxide in cosmetics product sample, giving results in excellent agreement with those obtained by standard method.

Determination of free glycerol in biodiesel at a platinum oxide surface using potential cycling technique

A novel, inexpensive and fast method based on the electrooxidation of glycerol on platinum electrodes by the potential cycling technique has been designed for the determination of free glycerol in biodiesel. A wide range of linearity was achieved between 15 and 150 mg L −1 (0.16 and 1.6 mmol L −1), which corresponds to concentrations ranging between 56 and 560 mg kg −1 (glycerol:biodiesel) for an extraction using 2 g biodiesel. A method for the fast extraction of glycerol from biodiesel with water followed by elimination of organic interferents has also been developed, so that the novel determination method can be applied to various biodiesel samples. The excellent repeatability allows determination of glycerol in numerous samples, with no need for recalibration.

Electrocatalytic oxidation of methanol on carbon paste electrode modified by nickel ions dispersed into poly (1,5-diaminonaphthalene) film

Poly (1,5-diaminonaphthalene) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 1.0 M nickel chloride solution. The electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. Also, cyclic voltammetric experiments showed that methanol electrooxidized at the surface of this Ni(II) dispersed polymeric modified carbon paste electrode [Ni/P-1,5-DAN/MCPE]. The mechanism of methanol oxidation changes from diffusion control at low concentration to a catalytic reaction at higher methanol concentration. The effects of both scan rate and methanol concentration on the anodic peak height of the methanol oxidation were discussed.

A cyclic voltammetric and coulometric study of a modified electrode prepared by electrooxidative polymerization of1,5-diaminonaphthalene in aqueous acidic medium

Abstract Poly 1,5-diaminonaphthalene films were prepared by using the repeated potential cycling technique and different amounts of charge in an aqueous acidic solution containing 0.1 M HClO 4 and 0.2 M NaClO 4 by sweeping the platinum electrode potential between 0.0 and 0.8 V at a scan rate of 20 mV/sec. The prepared film showed an electroactive redox response in acidic chloride solution. The factors affected the electroactivity of the film such as the scan repetition, the quantity of charge used during the film formation and the sweep rate were studied in details. No film was observed by utilizing controlled potential electrolysis. Comparative study between the stability and polymerization yield for the films prepared in acetonitrile and aqueous acidic solutions was carried out.