Electrocatalytic Oxidation Of Hydrogen Peroxide Research Articles

Single-Particle Spectroelectrochemistry: Promoting the Electrocatalytic Activity of Gold Nanorods via Oxygen Plasma Treatment without Structural Deformation.

Understanding of the electrocatalytic activity enhancement in gold nanoparticles is still limited. Herein, we present the effect of the oxygen plasma treatment on the electrochemical activity of gold nanorods (AuNRs). Oxygen plasma treatment resulted in the blueshift and line width narrowing of the localized surface plasmon resonance (LSPR) spectra obtained from individual AuNRs immobilized on an indium tin oxide (ITO) surface. These changes can be attributed to increases in the surface charges of the AuNRs. The formation of a Au-ITO heterojunction provided structural stability to the immobilized AuNRs regardless of the duration of oxygen plasma exposure. The electrocatalytic oxidation of hydrogen peroxide (H2O2) was induced by increases in the free-electron densities on the surfaces of these AuNRs owing to oxygen plasma treatment, and Au did not dissolve under the experimental conditions. However, the potential-dependent LSPR spectra of the individual AuNRs showed similar patterns of LSPR behavior, irrespective of the duration of oxygen plasma treatment and the concentration of H2O2. Therefore, this study based on single-particle spectroelectrochemistry and cyclic voltammetry improves the understanding of the role of oxygen plasma treatment in promoting the catalytic activity of structurally stable AuNRs immobilized on an ITO surface.

Facile Synthesis of Electrospun Nickel (II) Oxide Nanofibers and Its Application for Hydrogen Peroxide Sensing

AbstractThe aim of the present study is to report an alternative technique of creating nickel oxide (NiO) nanofibers, manufactured by facile and economical electrospinning process. The crystallinity nature of NiO nanofibers is investigated by X‐ray diffraction (XRD). Nanofibers morphology is examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The diameter of the nanofibers is varying from of 100–150 nm. Furthermore, Selected Area Electron Diffraction (SAED) pattern revealed that NiO nanofibers are exhibiting a single phase crystalline structure. The NiO nanofibers modified glassy carbon electrode (GCE) showed an excellent performance towards the electrocatalytic oxidation of hydrogen peroxide (H2O2). This sensor showed a wide range of detection from 10 μM to 50 mM, low limit of detection 0.33 μM and high sensitivity 42.09 μA μM−1cm−2 for H2O2 detection. The entire analysis reaffirms the suitability of NiO nanofibers as one of the futuristic sensing material for H2O2 detection.

Electrocatalytic Oxidation of Hydrogen Peroxide on the Graphite Electrode Based on Silver Nanoparticles

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.

Electrocatalytic oxidation of hydrogen peroxide on the surface of nano zeolite modified carbon paste electrode

This study investigated the use of synthesized nanozeolite Y to prepare modified carbon paste electrode for electrocatalytic oxidation of hydrogen peroxide. In order to prepare the modified electrodes, the nickel ions were doped to Y zeolite framework through ion exchange mechanism and the electrochemical behaviour of the proposed modified electrode was studied using the cyclic voltammetry technique. The obtained results revealed that modified carbon paste electrode in the form of Ni/NiYCPE is the best electrode for the oxidation of hydrogen peroxide in the alkaline media. The hydrogen peroxide transfer coefficient (α) and the current density were calculated as 0.54 and 6.7 mA/cm2, respectively. The catalytic rate constant (K) for this electrocatalytic reaction was calculated through the chronoamperometric technique (K = 0.43 × 104 cm2s−1mol−1).

Enhanced Electrochemical Oxidation of Hydrogen Peroxide at Hydroxyl Ion-Modified Gold Electrode in Alkaline Media

Chemisorption of hydroxyl ion (OH-) from aqueous solution of KOH at the polycrystalline gold (Au (poly)) electrode under stirring condition was studied. A pre-wave at ca. 0.19 V was observed due to partial discharging of the chemisorbed OH-. The linear plot of the pre-wave current vs. scan rate passed through the origin suggesting that it was associated with a surface confined process. An extraordinary enhanced electrocatalytic oxidation of hydrogen peroxide (HO - 2 ) at the in situ fabricated OH--modified Au (poly) (OH-ôAu (poly)) electrode was achieved. A mechanism of the observed catalytic activity was proposed on the basis of electrostatic attraction between the chemisorbed OH- and partial positively charged hydrogen (Hd+) of HO - 2 molecules.Journal of Bangladesh Academy of Sciences, Vol. 40, No. 2, 125-135, 2016

Imaging electrocatalytic processes on single gold nanorods.

Imaging electrochemical processes has attracted increasing attention in past decades. Particularly, monitoring electrochemical reactions rapidly at the nano-scale is still a challenge due to the ultra-low current detection and long scanning time required. The development of optical techniques provide a new way to demonstrate electrochemical processes through optical signals which enhance sensitivity and spatial resolution. Herein, we developed a novel method to image electrocatalytic processes on single gold nanorods (GNRs) during Cyclic Voltammetry (CV) scanning based on plasmon resonance scattering information by using dark-field microscopy. The electrocatalytic oxidation of hydrogen peroxide was selected as a typical reaction and the catalytic mechanism was revealed using the obtained spectra. Notably, observation on single GNRs avoided the averaging effects in bulk systems and confirmed that the individual nanoparticles had variable catalytic properties with different spectral change during the reaction process. Furthermore, a color-amplified system was introduced to convert light intensity into imaging information via the Matlab program which was able to image thousands of nanoparticles simultaneously. This approach offered the statistical intensity distribution of all of the nanoparticles in a dark-field image which dramatically enhanced the detection accuracy and avoided random events.

Reactivity indexes for the electrocatalytic oxidation of hydrogen peroxide promoted by several ligand-substituted and unsubstituted Co phthalocyanines adsorbed on graphite

The electrocatalytic activity of metal phthalocyanines is controlled by their coordination chemistry and their ability to bind the reacting molecules as extra-planar ligands. This chemistry is controlled by the nature of both the metal and the ligand, the latter affecting the electron density located on the metal, which is the active site. In this work we have examined the electrocatalytic activity of several Co phthalocyanines having electron-donating or electron-withdrawing substituents on the ligand in order to modulate the electron density on the metal center and the binding energy of peroxide to the active site. We have found that the active species is Co(II) and the catalytic activity as logi at constant E varies linearly with E°′, the Co(II)/(I) and Co(III)/(II) formal potentials of the catalyst. Essentially, these results indicate that in order to improve the electrocatalytic activity of Co phthalocyanines it is required to prepare complexes with ligands having more powerful electron-donating substituents, in order to shift the formal potential of the complex to more negative values and decrease the binding energy of peroxide to the metal.

New insights into electrocatalysis based on plasmon resonance for the real-time monitoring of catalytic events on single gold nanorods.

Gold nanoparticles (GNPs) have been widely applied in industrial catalysis and electrocatalysis. Owing to their wide variety of shapes, sizes, and compositions, a range of different catalytic properties is possible. Thus, it is important to monitor catalytic processes and their mechanisms on single GNP surfaces to avoid averaging effects in bulk systems. Therefore, a novel method based on dark-field scattering spectroscopy was developed to monitor, in real-time, the electrocatalytic oxidation of hydrogen peroxide on a single gold nanoparticle surface. The catalytic mechanism was revealed via the plasmon resonance scattering spectral shift of single gold nanorod with the elimination of bulk effect. Moreover, we found that the presence of chloride ions could block the catalytic activity of nanorods for the oxidation of H2O2. Most importantly, it was discovered that individual nanoparticles have variable properties with different spectra shifts during the catalytic process. The obtained optical signals from individual nanorods not only offer versatile information regarding the reaction but also improve the understanding of electrochemistry and the catalysis mechanism of single nanoparticles.

Electrocatalytic Oxidation of Hydrogen Peroxide at a Sol‐gel Derived Carbon Ceramic Electrode Modified with Copper Iodide

AbstractA novel modified carbon ceramic electrode using CuI as modifier was fabricated. The copper iodide modified sol‐gel derived carbon ceramic (CIM‐SGD‐CC) electrode has high catalytic ability for electrooxidation of hydrogen peroxide. The charge transfer coefficient (α) and exchange current density (j0) for the modified electrode were calculated. It has been shown that using the CIM‐SGD‐CC electrode, hydrogen peroxide can be determined by cyclic voltammetry and amperometry with limit of detections 26 and 0.31 μmol L−1, respectively. The advantages of the modified CCE are its good stability and reproducibility of surface renewal by simple polishing, excellent catalytic activity.

Electrocatalytic oxidation of hydrogen peroxide on a platinum electrode in the imitation of oxidative drug metabolism of lidocaine

Electrochemistry in combination with mass spectrometry has shown promise as a versatile technique not only in the analytical assessment of oxidative drug metabolism, but also for small-scale synthesis of drug metabolites. However, electrochemistry is generally limited to reactions initiated by direct electron transfer. In the case of substituted-aromatic compounds, oxidation proceeds through a Wheland-type intermediate where resonance stabilization of the positive charge determines the regioselectivity of the anodic substitution reaction, and hence limits the extent of generating drug metabolites in comparison with in vivo oxygen insertion reactions. In this study, we show that the electrocatalytic oxidation of hydrogen peroxide on a platinum electrode generates reactive oxygen species, presumably surface-bound platinum-oxo species, which are capable of oxygen insertion reactions in analogy to oxo-ferryl radical cations in the active site of Cytochrome P450. Electrochemical oxidation of lidocaine at constant potential in the presence of hydrogen peroxide produces both 3- and 4-hydroxylidocaine, suggesting reaction via an arene oxide rather than a Wheland-type intermediate. No benzylic hydroxylation was observed, thus freely diffusing radicals do not appear to be present. The results of the present study extend the possibilities of electrochemical imitation of oxidative drug metabolism to oxygen insertion reactions.

Electrocatalytic Oxidation of Hydrogen Peroxide Based on the Shuttlelike Nano-CuO-Modified Electrode

CuO nanocrystals were prepared with hydrothermal synthesis method. The morphology of the nano-CuO was characterized by scanning electron microscopy. The prepared shuttlelike CuO nanocrystals were modified to glass carbon electrode (GCE) to form nano-CuO/GCE modified electrode. The obtained modified electrode showed an excellent electrocatalytic property towards hydrogen peroxide in 0.01 M NaOH containing 0.09 M KCl electrolyte. Under the optimal experiment conditions, the electrocatalytic response current of this sensor was proportional to the H2O2concentration in the range of 0.02 μM~250 μM with a detection limit down to 7 nM (signal/noise = 3). The sensitivity was calculated to be 227 μA/mM. The H2O2sensor exhibited low detection limit, fast response time, and good reproducibility and could be applied to determine hydrogen peroxide.

Electrocatalytic Oxidation of Hydrogen Peroxide Using Iodide as Mediator; Application for its Simple and Selective Determination

AbstractThe electrocatalytic oxidation of hydrogen peroxide has been studied by iodide at the surface of carbon paste electrode. Cyclic voltammetry and chronoamperometry techniques were used to investigate the suitability of iodide as a mediator for the electrocatalytic oxidation of hydrogen peroxide in aqueous solution with various pH. Results showed that pH 8.00 is the most suitable for this purpose. The kinetic process of the catalytic reaction can be explained using cyclic voltammetry and chronoamperometry. The calculated mean value of catalytic rate constant (kh) is determined to be 6.46 × 102 M−1s−1 using chronoamperometry data. In order to obtain the diffusion coefficient of iodide, chronoamperometry method has been used, that the value of D has been calculated 7.16 × 10−1 cm2 s−1. The catalytic oxidation peak current was linearly dependent on the hydrogen peroxide concentration and the linearity range obtained was 1.00 × 10−5 to 1.00 × 10−3 M. Detection limit has been found to be 5.61 × 10−6 M (3σ;). This method can provide a simple and low cost electrochemical sensor for catalytic oxidation detection of hydrogen peroxide in real sample.

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.

Graphene modified basal and edge plane pyrolytic graphite electrodes for electrocatalytic oxidation of hydrogen peroxide and β-nicotinamide adenine dinucleotide

Graphene was cast on basal and edge plane pyrolytic graphite electrodes for electrochemical applications. The morphology of the resulting graphene modified electrode was investigated by atomic force microscopy. In cyclic voltammetric responses, both anodic and cathodic peak currents varied linearly with the square root of scan rates over the range of 25–600 mV in 0.1 M KCl containing 5 mM Fe ( CN ) 6 4 - at graphene modified basal and edge plane pyrolytic graphite electrodes, which suggests a diffusion-controlled process. The graphene modified basal and edge plane pyrolytic graphite electrodes exhibited the abilities to lower the electrooxidation potentials of β-nicotinamide adenine dinucleotide and hydrogen peroxide in comparison with bare basal and edge plane pyrolytic graphite electrodes. The electrocatalytic behavior obtained at the graphene modified basal and edge plane pyrolytic graphite electrodes may led to new applications in electroanalysis.

Electrochemical and <I>In Situ</I> Spectroelectrochemical Studies on the Gold Nanoparticles Co-Deposited with Cobalt Hexacyanoferrate Modified Electrode and Its Application in Sensor

Gold nanoparticles (Aunano) co-deposited with cobalt hexacyanoferrate (CoHCF) modified electrode was prepared by electrodeposition on glassy carbon electrode (represented as GC/Aunano-CoHCF) and characterized. The surface morphology of the modified electrode was studied by AFM and the electrochemical properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The co-deposition of Aunano with CoHCF improved the electrochemical behavior of the Aunano-CoHCF modified electrode when compared to CoHCF modified electrode. The in-situ spectroelectrochemical changes of Aunano-CoHCF modified electrode was studied to understand the redox switching of CoHCF in the presence of Aunano. The in-situ spectral study showed that the co-deposited Aunano with CoHCF acted as nanoelectrode and improved the electron transfer and redox switching processes when compared to CoHCF modified electrode. An enhanced electrocatalytic oxidation of hydrogen peroxide (H2O2) was observed at the GC/Aunano-CoHCF electrode with an onset potential of 0.5 V when compared to GC/CoHCF electrode. The poly Au electrode did not show a similar oxidation peak for H2O2 oxidation. The Aunano co-deposited with CoHCF (GC/Aunano-CoHCF) significantly enhanced the electrocatalytic property of CoHCF. The amperometric detection of H2O2 was studied at the CoHCF modified electrode in the presence and absence of Aunano and poly Au electrode. The GC/Aunano-CoHCF electrode showed fast sensing response and lower detection limit for H2O2 when compared to GC/CoHCF and poly Au electrode. The electrochemical, in situ spectroelectrochemical and electrocatalytic properties of Aunano co-deposited with CoHCF clearly showed that the GC/Aunano-CoHCF electrode could be used as an electrochemical sensor.

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.

Direct Electrocatalytic Oxidation of Hydrogen Peroxide Based on Nafion and Microspheres MnO2 Modified Glass Carbon Electrode

Direct Electrocatalytic Oxidation of Hydrogen Peroxide Based on Nafion and Microspheres MnO2 Modified Glass Carbon Electrode

Study on the Electrochemical Behavior of Ferric Stearate and its Electro-Catalytic Oxidation of Hydrogen Peroxide

A ferric stearate electrode was made by doctor-blade methods using the Fluorine tin oxide (FTO) conductive glass. The electrochemical behavior of ferric stearate electrode was studied by the cyclic voltammetry. The electro-catalytic effects of ferric stearate on H2O2 were also investigated by cyclic voltammetry.

Nano TiO 2–Au–KI film sensor for the electrocatalytic oxidation of hydrogen peroxide

A glassy carbon and indium tin oxide (ITO) electrodes have been modified with the nano TiO 2–Au–KI film by the adsorption of TiO 2 nanoparticles on the electrodes followed with the electrochemical depositions of nano Au and KI film. Further the nano TiO 2–Au–KI film modified ITO was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. From the microscopic results, the adsorbed nano TiO 2 particles size were found in the range of 70–100 nm. Here the electrochemical depositions of nano Au were formed as a flower shape were in the size range of 230 nm to 1 μm. Next the electrochemical behavior of nano TiO 2–Au–KI film has been examined in different pH solutions. The nano TiO 2–Au–KI film modified glassy carbon electrode (GCE) showed good electrocatalytic activity towards the oxidation of H 2O 2 in phosphate buffer solutions (pH 7.0). The linear range of detection for H 2O 2 oxidation using nano TiO 2–Au–KI film was found as 1 × 10 −5 to 1 × 10 −4 M and 1 × 10 −9 to 1 × 10 −7 M in CV and differential pulse voltammetry (DPV) techniques. The practical applications of nano TiO 2–Au–KI film was evaluated by analyzing the real samples such as antiseptic and contact lens cleaner solutions containing H 2O 2.

Electrocatalytic Behavior of Self-assembled Monolayer of a Novel Tetraazamacrocyclic Copper(II) Complex in Ascorbate Oxidation

Self-assembled monolayers (SAMs) of alkanethiols on gold have been used as a powerful method to prepare a chemical interface which is stable and structurally welldefined monolayer with a controllable thickness and desirable function. These characteristics of a SAM make them ideal model systems to study both fundamental and practical issues such as catalysis, electro-optic devices, sensors, corrosion, lubrication, adhesion, molecular recognition, and electron/energy transfer. In particular, a SAM can offer specific properties and selectivity to the chemical interface if a terminal group of the SAM is redox active for the functions of the monolayer-modified electrode surface. The transition metal complexes of macrocyclic ligands have been extensively investigated in solution because they are very useful in design and development for anion recognition recepter as well as effective electrocatalyst. In addition, they play an important role in biological process catalyzing the dismutation of a toxic superoxide radical (O2 −) to hydrogen peroxide and water. However, there have been only a few studies on the SAMs of transition metal-macrocyclic ligand complex. Ohsaka et al. reported an electrocatalytic oxidation of hydrogen peroxide using SAM of Ni(II)-pentaazamacrocyclic complex on gold. Bilewitz and co-workers studied the role of SAM of a Cu(II)-tetraazamacrocyclic complex in ascorbate oxidation catalysis. With a view to developing new type of dismutase mimic and catalase active site containing transition metal ion, we have synthesized a novel tetraazamacrocyclic ligand L (shown in Figure 1) which can not only complex with a transition metal(II) ion in solution but also contains long alkylthiol as a head group for anchoring the electroactive macrocyclic complex to the gold electrode surface. In this communication, we report elecctrocatalytic behavior of the SAM consisted of Cu(II) complex of the ligand L in oxidation of ascorbic acid. There are considerable interests for this type of copper(II) complexes because of development of an effective superoxide dismutase mimic and in their immobilization on electrode in order to obtain new catalytically active interface. First of all, the electroactive Cu(II) complex of L (abbreviated as CuL) has been easily synthesized in situ by dropping 5 mM CuCl2 methanol solution into 1 mM L in methanol. In order to find out the ratio of metal to ligand in the CuL complex formation reaction, the absorbance of CuL was monitored and the complex showed an absorbance maximum at 600 nm. In the spectroscopic titration, the absorbance was increased up to the equivalent point and then was not changed to the continuous addition of Cu(II) solution. We have observed the stoichiometric equivalents of Cu cation and L at the equivalent point. This exactly indicates that Cu(II) complexes of 1 : 1 Cu(II) : L are produced in the titration reaction. In order to modify gold electrode with the SAM of CuL, a clean keyhole-shaped Au thin film electrode was immersed for 12 h in the methanolic mixture solution containing the same equivalents of CuCl2 and L (1 mM) after the solution was stirred for a few minutes. As an alternative to prepare the SAM of CuL on gold, we have tried to make coordination of Cu into the macrocyclic ring of L which has been already covalently immobilized onto the gold surface via Au-thiolate bond. From cyclic voltammetric measurement, this method was found to be not effective to obtain a full coverage of Cu-complexation at the interface of SAM of L. It might be due to compact two-