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Journal Cover Electrocatalysis
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1868-2529 - ISSN (Online) 1868-5994
     Published by Springer-Verlag Homepage  [2210 journals]   [SJR: 0.542]   [H-I: 7]
  • Recent Advances in Microbial Electrocatalysis
    • Abstract: Abstract Microbial electrocatalysis is a relatively new field of research in which the intrinsic metabolic capacities of various microbes are coupled with inorganic electrodes to carry out interesting chemical conversions. Given the great diversity in microbial metabolic pathways, a wide variety of processes are possible and have been demonstrated in principle. The generation of electrical currents coupled with the degradation of wastes or the capture of light energy is under extensive investigation. This area has seen the greatest development with an over tenfold increase in power densities in the past decade. A relatively new development is electrosynthesis, the electrically driven fixation of CO2 into various chemicals. Moreover, microbial electrochemical devices can be used to carry out desalination or “unbalanced” chemical conversions. Microbial electrocatalysis has the advantages of the exquisite specificity and regioselectivity of biochemical reactions coupled with the robustness and self-duplicating properties of living systems. Here, recent advances in this area are reviewed with significant achievements highlighted. As well, the major factors limiting practical application are discussed along with future directions for improvement.
      PubDate: 2014-10-01
  • Comparative Study of the Electrocatalytically Active Surface Areas (ECSAs)
           of Pt Alloy Nanoparticles Evaluated by H       class="a-plus-plus">upd and CO-stripping
    • Abstract: Abstract This study intends to provide some insight in the up-to-date elusive assessment of a correct choice of method for estimating the active surface area of Pt alloy nanoparticle catalysts. Taking PtNi3 nanoparticles as an example, we have compared three types of electrochemically active surface area (ECSA) data, CO-ECSA, Hupd-ECSA, and Hupd/CO-ECSA, which were evaluated from CO stripping and underpotentially deposited hydrogen stripping steps applied at different times along a reference catalyst activity test protocol. Considering a total of six different detailed voltammetric test protocols, we address Pt alloy particle size effects, analyze the effect of the time of application of CO and hydrogen stripping, and study their effect on the Pt mass and Pt surface-specific activities for the oxygen reduction reaction (ORR). In a discussion of the ratio of CO charge to hydrogen charge, it is shown that this quantity is more complex than previously thought and not associated with a specific surface structure. The Hupd/CO-ECSA data are found to be a reasonable balance for the estimate of surface area normalized, so-called specific catalytic ORR activities.
      PubDate: 2014-10-01
  • Ethylene Glycol Oxidation at Pt/TiO       class="a-plus-plus">2/Carbon Hybrid Catalysts
           Modified Glassy Carbon Electrodes in Alkaline Media
    • Abstract: Abstract Biomass-based fuels in conjunction with direct alcohol alkaline fuel cells are an emerging technology that may be able to wean us of our dependency of fossil fuels. However, their adoption is stalled by their high production costs (i.e., precious metal loading) and low electrocatalytic efficiencies. In this study, the platinum loading of 20 % Pt/C catalyst for use in ethylene glycol electrooxidation was reduced by mixing with TiO2 nanopowder in different mass ratios. This was followed by surface activation and cyclic voltammograms of the hydrogen adsorption and Pt oxide potential regions in 0.1 M KOH showed peak potential changes that are attributed to platinum interactions with TiO2. The catalysts were further tested for the electrochemical oxidation of ethylene glycol in alkaline media, where the titanium-modified catalysts showed a maximum increase in peak current density by 91 %, when compared to the commercial Pt/C catalyst. When the peak current was normalized by Pt surface area and mass, a maximum increase of 322 % was found. Tafel plot analysis showed increased exchange currents for the rate determining step of ethylene glycol oxidation at Pt/TiO2/C hybrid catalysts up to 7.35 × 10−7A/cm2. This is nearly 8.7 times larger than, 8.47 × 10-8A/cm2, the ethylene glycol exchange current density for the rate determining step in commercial Pt/C catalysts. Finally, chronoamperometric studies showed that the hybrid catalysts possessed increased stability and activity for ethylene glycol electrooxidation in 0.1 M ethylene glycol in 0.1 M KOH at an applied potential of −0.350 V vs. Ag/AgCl. This study shows that TiO2 can modify the platinum surface catalyst activity without the need of a TiO2 support. This avoids loss in electrical conductivity of the catalyst and lowers the total catalyst mass without sacrificing catalytic mass activity.
      PubDate: 2014-10-01
  • Photoelectrocatalytic Degradation of Ofloxacin Using Highly Ordered
    • Abstract: Abstract Ofloxacin has been widely used as a form of quinolone antibiotics. However, it has the potential to exert biological effects on aquatic organisms and cause surface water pollution. It is necessary to find an efficient way to remove ofloxacin. This study reports on the degradation of ofloxacin in solution using TiO2 nanotubes (TiO2 NTs) as photocatalyst. The TiO2 NTs were synthesized through anodization. The morphology, elemental composition and state, crystalline phase, and photocatalytic activity of this photocatalyst were characterized by a variety of surface analysis techniques. The obtained TiO2 NTs were applied to ofloxacin degradation by photoelectrocatalysis. The degradation efficiency was assessed by in situ monitoring the UV-vis absorbance spectrum of ofloxacin solution during the degradation process. The effects of initial pH, bias potential, and initial concentration of ofloxacin were investigated systematically. Moreover, the toxicity of ofloxacin during the photoelectrocatalytic degradation process was evaluated using the growth inhibition test with Microcystis aeruginosa. The TiO2 NT-based photoelectrocatalytic method provided a high degradation rate for ofloxacin removal.
      PubDate: 2014-10-01
  • The Influence of Pt Oxide Film on the Activity for the Oxygen Reduction
           Reaction on Pt Single Crystal Electrodes
    • Abstract: Abstract Correlation between Pt oxide and the activity for the oxygen reduction reaction (ORR) has been investigated on the low index planes of Pt (Pt(111), Pt(100), and Pt(110)) using voltammogram and rotating disk electrode (RDE). Pt oxide is formed by holding the potential at 1.0 V vs. RHE. The ORR activity decreases with the increase of the time of Pt oxide formation. The order of the ORR activity is Pt(100) < Pt(111) < Pt(110) in 0.1 M HClO4 after the formation of Pt oxide. This order is identical with that without Pt oxides. Formation of hardly reducible Pt oxide deactivates the ORR activity on Pt(111) remarkably. The amount of Pt oxides (PtOH, PtO and hardly reducible Pt oxide) increases as Pt(100) < Pt(111) < Pt(110) at 1.0 V.
      PubDate: 2014-10-01
  • High-Performance and Durable Membrane Electrode Assemblies for
           High-Temperature Polymer Electrolyte Membrane Fuel Cells
    • Abstract: Abstract Membrane electrode assemblies (MEAs) with gas diffusion electrodes (GDEs) fabricated by various catalyst layer (CL) deposit technologies were investigated for the application of high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The physical properties of the GDEs were characterized by scanning electron microscopy (SEM) and pore size distribution. The electrochemical properties were evaluated and analyzed by polarization curve, Tafel equation, electrochemistry impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results showed that the electrodes prepared by ultrasonic spraying and automatic catalyst spraying under irradiation (ACSUI) methods have superior CL structure and high electrochemistry activity, resulting in high fuel cell performances. Durability tests revealed the feasibility of the electrodes for long-term HT-PEMFC operation.
      PubDate: 2014-10-01
  • Let’s Not Ignore the Ultrasonic Effects on the Preparation of Fuel
           Cell Materials
    • Abstract: Abstract This article is a follow-up paper recently published entitled ‘The importance of ultrasonic parameters in the preparation of fuel cell catalyst inks’ [1] describing the effect of low-frequency high-power ultrasound on the catalyst ink composition used for the fabrication of fuel cell electrodes. In this paper, it was shown that care should be taken when using low-frequency ultrasound whereby (i) the ultrasonic parameters such as frequency, power and duration may affect the final ink composition and rheology and therefore its electrochemical performance, (ii) the ultrasonic equipment (and make), frequencies, powers, durations and the distance between the vibrating source and the reaction vessel should be reported, (iii) the catalyst ink temperature should be monitored and regulated during the course of the experiment, (iv) immersing the ultrasonic probe into the solution may lead to contamination (arising from the erosion of the titanium alloy vibrating tip) and (v) high-shear mixing of the catalyst inks using rotor-stator mixers at high rotation speed in silent conditions should be performed, analysed and compared to ultrasonicated samples for consistency and comparison purposes between studies. A careful and systematic approach should be adopted due to the fact that low-frequency ultrasound is known to be an intensification technology offering remarkable advantages: (a) an increase in fluid degasification, de-agglomeration (and particle size reduction), dispersion, homogenisation, emulsification, atomisation, molecular degradation and chemical rates and yields and (b) an improvement of surfaces due to very efficient cleaning (mainly erosion). These ultrasonic effects are known to be caused by (a) an increase in mass transfer and heat transfer induced by extreme solution ‘mixing’ and (b) the production of cavitation bubbles undergoing very short and violent collapse within the fluid generating local ‘hotspots’ of high energy (temperatures of up to 5,000 K and pressures of up to 2,000 atms), leading to (i) radicals formation and (ii) jets of liquid of high velocity (up to 200 m s−1) near surfaces.
      PubDate: 2014-10-01
  • The Effect of TiO2 on
           the Catalytic Activity of a PtRu/C Catalyst for Methanol Oxidation
    • Abstract: Abstract In this work, the effect of the addition of different amounts of TiO2 nanotubes to a PtRu catalyst supported on Vulcan XC-72R carbon black for methanol oxidation was studied. Two approaches were used for the catalyst preparation. In the first case, Pt and Ru metal ions were impregnated onto the support (C-TiO2) and subsequently reduced with NaBH4. In the second case, the metal ions were first reduced and then impregnated, in order to obtain a catalyst with metal loading of 30 % of PtRu (50:50 at.% composition of Pt/Ru) and varying concentrations of TiO2 (5–15 wt%); the actual composition was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. The electrochemical properties were studied via cyclic voltammetry and chronoamperometry in 0.5 M H2SO4 solution. X-ray diffraction analyses indicated the formation of PtRu alloy with different degrees of alloying. The CO-stripping voltammetry studies showed that both the onset potential and the peak potential are dependent on the catalyst composition; the PtRu/C-TiO2(10) exhibited a relatively higher CO oxidation current compared to those exhibited by the other catalysts. Both the linear sweep voltammetry and the chronoamperometric results also demonstrated that the PtRu/C-TiO2(10) catalyst exhibited a higher methanol oxidation current and a lower poisoning rate among the investigated catalysts with various TiO2 nanotube contents (i.e., 0, 5, and 15 % TiO2). The prepared catalysts revealed essentially the same catalytic performance independently of the procedure used for their preparation.
      PubDate: 2014-10-01
  • Electrocatalytic Properties of Co-Mo Alloys Electrodeposited from a
           Citrate-Pyrophosphate Electrolyte
    • Abstract: Abstract The electrocatalytic activity of electrodeposits of cobalt and Co-Mo alloys in the electroreduction reaction of hydrogen evolution in an acid, neutral and alkaline media has been studied in this work. To deposit coatings, a nontoxic citrate-pyrophosphate electrolyte was used, which was proposed earlier. It has been found that the alloys having the same chemical composition but a different phase composition can exhibit different electrocatalytic activity. The best electrolyte for the making of catalytically active Co-Mo alloys, for which the decrease in hydrogen evolution overpotential as compared with pure cobalt is about 400 mV at 30 mA cm−2 in alkaline solution, is solution with the cobalt and molybdenum concentration ratio 10:1.
      PubDate: 2014-10-01
  • Investigation of a Polyaniline-Coated Copper Hexacyanoferrate Modified
           Glassy Carbon Electrode as a Sulfite Sensor
    • Abstract: Abstract A polyaniline-coated copper hexacyanoferrate modified glassy carbon electrode (PANI/CuHCF/GC) was successfully prepared by cyclic voltammetry, which had higher electrocatalytic activity and good stability toward the oxidation of sulfite. The mechanism and main factors of influencing the electrocatalytic activity for the preparation of PANI/CuHCF/GC were investigated. The results indicated that the optimal concentration of K3Fe(CN)6–CuCl2 (molar ratio of 1:1) and aniline, scanning number of CuHCF particles deposition, and aniline polymerization were 0.6 μmol·L−1, 13, and 15, respectively. The PANI/CuHCF/GC surface properties were characterized by scanning electron microscopy and AC impedance spectra, whose results indicated that CuHCF particles evenly attached to GC surface and the electron transfer impedance was significantly reduced. Sulfite was detected by an amperometric-time (i–t) method, whose linear equation, linear range, and detection limit were Δi (μA) = 0.0624 + 46.42c mmol·L−1 (n = 15, R = 0.9978), 4.3 × 10−6 to 3.9 × 10−4 mol·L−1 and 0.6 μmol·L−1 (S/N = 3), respectively. The response time was less than 1 s. The interference of some common potential substances toward sulfite determination was studied, whose results indicated that PANI/CuHCF/GC electrode had strong anti-interference ability. The PANI/CuHCF/GC was successfully applied to the detection of sulfite in real samples with satisfactory results.
      PubDate: 2014-10-01
  • Impedance Spectroscopy and Catalytic Activity Characterization of a
           La0.85Sr       class="a-plus-plus">0.15MnO       class="a-plus-plus">3/Ce       class="a-plus-plus">0.9Gd       class="a-plus-plus">0.1O       class="a-plus-plus">1.95 Electrochemical Reactor
           for the Oxidation of Propene
    • Abstract: Abstract This study aims to characterize the catalytic and electrochemical behavior of a La0.85Sr0.15MnO3/Ce0.9Gd0.1O1.95 porous reactor for the oxidation of propene in the presence of oxygen. The application of anodic polarization strongly increased the propene oxidation rate up to 71 %, although the current efficiency remained low. The effect of prolonged polarization on the reactor catalytic activity was evaluated. Prolonged polarization enhanced both the reactor intrinsic catalytic activity and the electrode performance due to the formation of oxygen vacancies on the electrode surface. Electrochemical impedance spectroscopy was used to investigate the effect of propene introduction on the reactor impedance response. The introduction of propene into reactive system caused a strong increase of electrode resistance, mainly located in the low-frequency region of the impedance spectrum. This effect was caused by the strong adsorption of propene on electrode surfaces inhibiting the adsorption and dissociation of oxygen.
      PubDate: 2014-10-01
  • Non-precious Metal Oxygen Reduction Reaction Catalysts Synthesized Via
           Cyanuric Chloride and        class="a-plus-plus">N-Ethylamine
    • Abstract: Abstract Non-precious metal oxygen reduction reaction catalysts were synthesized in this study using novel and cheap nitrogen sources, cyanuric chloride, and N-ethylamine. These materials presented a promising catalytic activity toward the oxygen reduction reaction (ORR) in acid media, which is the most challenging. For the catalyst based on N-ethylamine, the onset potential for ORR is 0.803 V vs reversible hydrogen electrode (RHE) or 0.703 V at 0.1 mA cm−2. The nitrogen source is shown to be extremely important in the final morphology and ORR activity of the catalyst. Steady state ORR polarizations evidenced that the final morphology of the catalysts play a major rule on mass transport in this class of catalysts, with a lamella-like structure being detrimental. Physical characterizations of the catalysts revealed that cyanuric chloride promotes morphology alterations to the carbon support toward a lamella-like structure, while the catalysts synthesized from N-ethylamine retained the nanoparticle structure of the carbon precursor. This catalyst exhibited a Tafel slope of 66 mV per current decade in the lower potential region, with promising four-electron selectivity in a polymer electrolyte fuel cell (PEFC) operational potential.
      PubDate: 2014-10-01
  • Preparation and Electrocatalytic Properties of Polydopamine Functionalized
           Reduced Graphene Oxide-Silver Nanocomposites
    • Abstract: Abstract Polydopamine functionalized reduced graphene oxide-silver nanoparticle (PDA-RGO/Ag NP) nanocomposites were successfully prepared by a simple and mild procedure. Graphene oxide (GO) sheets were firstly coated with PDA via a self-polymerization process which provided an excellent interface for in-situ growing silver nanoparticles. Fourier transform infrared spectroscopy (FTIR) confirmed the successful coating of PDA and informed the reduction of the surface functional groups of GO. The formation of reduced GO and silver NPs was further evidenced by UV-Vis and X-ray diffraction spectroscopy. The as-prepared PDA-RGO/Ag nanocomposites could greatly enhance the electrochemical reduction of hydrogen peroxide (H2O2). This excellent performance was attributed to the increased effective electrode surface area due to the deposition of nano-sized Ag particles and graphene. The PDA-RGO/Ag-based electrochemical sensor displayed a rapid amperometric response for H2O2 measurement with a wide linear range from 0.5 μM to 8 mM and a low detection limit of 2.07 μM.
      PubDate: 2014-08-05
  • Electrochemical Growth of Surface Oxides on Nickel. Part 3: Formation of
           β-NiOOH in Relation to the Polarization Potential, Polarization Time,
           and Temperature
    • Abstract: Abstract Electro-oxidation of surface β-Ni(OH)2 residing on metallic Ni to β-NiOOH was studied in 0.5 M aqueous KOH at 277 K ≤ T ≤ 318 K by means of cyclic voltammetry (CV) and chrono-amperometry (CA). The process is accompanied by a diffusion of H+ within the surface oxide phase. The formation of β-NiOOH gives rise to an anodic peak in CV profiles, the potential of which depends on the scan rate (s). An analysis of the relation between the anodic peak current density (j peak, AN) and s indicates that the growth of β-NiOOH is controlled by the diffusion of H+ and its modelling leads to the determination of the diffusion coefficient of H+ (D(H+)). In the case of 277 K ≤ T ≤ 318 K, the values of D(H+) are of the order of 10–11 cm2 s–1, when calculated with respect to the electrode’s geometric surface area (A geom), and of the order of 10–12 cm2 s–1, when calculated with respect to the electrochemically active surface area (A ecsa). The activation Gibbs energy of H+ diffusion (Δdiff G ≠(H+)) is in the 19.5–22.6 kJ mol–1 range. Chrono-amperometry transients for the formation of β-NiOOH are analyzed on the basis of finite-space diffusion, with the assumption that β-NiOOH can be formed through three mechanistic pathways. The values of D(H+) determined for both A geom and A ecsa using this approach are of the order of 10–12 cm2 s–1. They are smaller than the analogous values of D(H+) determined on the basis of CV measurements but the values of Δdiff G ≠(H+) obtained using these two experimental approaches are comparable.
      PubDate: 2014-07-20
  • On the Temperature Dependence of Hydrogen Evolution Reaction at Nickel
           Foam and Pd-Modified Nickel Foam Catalysts
    • Abstract: Abstract This communication reports on hydrogen evolution reaction (HER), studied at Ni foam and Pd-activated nickel foam materials in 0.1-M NaOH solution over the temperature range of 20–60 °C. Catalytic modification of Ni foam leads to significant facilitation of temperature-dependent HER kinetics, manifested through radically reduced values of charge-transfer resistance parameter, as well as substantially modified Tafel polarization curves. The presence of a catalytic additive (Pd) is evidenced through scanning electron microscopy (SEM) analysis.
      PubDate: 2014-07-17
  • CO2 Electroreduction
           on Cu-Modified Platinum Single Crystal Electrodes in Aprotic Media
    • Abstract: Abstract Techniques of electrode modification by copper deposits are developed that allow obtaining compact bulk quasi-epitaxial deposits on basal Pt(hkl) single crystal faces. The issues of the deposit roughness and characterization are discussed. Problems of drying and transferring electrodes with copper deposits into other solutions are considered. The obtained deposits are used for CO2 electroreduction in propylene carbonate and acetonitrile solutions of 0.1 M TBAPF6, and the relationship between the electrode surface structure and its electrocatalytic activity in CO2 electroreduction is discussed. We also demonstrate that the restructuring of Cu deposits occurs upon CO2 electroreduction. Complementary reactivity studies are presented for bare Pt(hkl) and Cu(hkl) single crystal electrodes. Cu-modified Pt(hkl) electrodes display the highest activity as compared to bare Pt(hkl) and Cu(hkl). Particularly, the Cu/Pt(110) electrode shows the highest activity among the electrodes under study. Such high activity of Cu/Pt(hkl) electrodes can be explained not only by the increasing actual surface area but also by structural effects, namely by the presence of a large amount of specific defect sites (steps, kinks) on Cu crystallites.
      PubDate: 2014-07-16
  • Electrochemical Behaviour of PSS-Functionalized Silica Films Prepared by
           Electroassisted Deposition of Sol–Gel Precursors
    • Abstract: Abstract Porous, electrically insulating SiO2 layers containing polystyrene sulfonate (PSS) were deposited on glassy carbon electrodes by an electrochemically assisted deposition method. The obtained material was characterized by microscopic, spectroscopic and thermal techniques. Silica-PSS films modify the electrochemical response of the glassy carbon electrodes against selected redox probes. Positively charged species show reduced diffusivities across the SiO2-PSS pores, which resulted in a concentration ratio higher than 1 for these species. The opposite behaviour was found for negatively charged redox probes. These observations can be interpreted in terms of the different affinity of the GC/SiO2-PSS-modified electrode for the electroactive species, as a consequence of the negatively charged porous silica.
      PubDate: 2014-07-04
  • Electrocatalytic Oxygen Evolution on Electrochemically Deposited Cobalt
           Oxide Films: Comparison with Thermally Deposited Films and Effect of
           Thermal Treatment
    • Abstract: Abstract Electrocatalytic cobalt oxide layers have been prepared on nickel substrates using thermal decomposition and electrochemical deposition methods. Importantly, it was confirmed that the electrochemical deposition method could be applied to nickel foam substrates for use in zero-gap alkaline water electrolysis cells. The oxide layers produced were then investigated for their activity towards the oxygen evolution reaction in 30 wt % KOH solution and found to be superior compared with the uncoated nickel substrate. Layers produced by both methods had similar electrochemical behaviour, provided that the layers were annealed at temperatures ≥350 ∘C. This thermal treatment was required to mechanically stabilise the electrochemically deposited cobalt oxide layer. Due to this finding, the effect of annealing temperature was investigated for the electrochemically deposited layer, and it was found that the overpotential for oxygen evolution increased with increasing annealing temperature. Using cyclic voltammetry and impedance spectroscopy, it is concluded that the decrease in performance with increasing annealing temperature is largely caused by the corresponding decrease in active surface area. However, for annealing temperatures ≥400 ∘C, additional resistances are introduced that cause lower performance. The impedance data suggest that these additional resistances are caused by either a decrease in the conductivity of the cobalt oxide layer itself, or the formation of a passivating-like nickel oxide layer between the active cobalt oxide and the nickel substrate, or both. The resistances’ dependence on potential suggests that they originate from a semi-conducting material and these additional resistances ultimately give rise to non-linear Tafel behaviour.
      PubDate: 2014-06-22
  • Electrochemical and Fuel Cell Evaluation of PtIr/C Electrocatalysts for
           Ethanol Electrooxidation in Alkaline Medium
    • Abstract: Abstract PtIr/C electrocatalysts prepared by borohydride reduction process were characterized by X-ray diffraction, transmission electron microscopy, and cyclic voltammetry. The X-ray diffraction measurements suggested the PtIr alloy formation; furthermore, peaks of IrO2 were not observed; nevertheless, the presence of Ir oxides in small amounts and amorphous forms cannot be discarded. The transmission electron microscopy showed the average particle diameter between 4.0 and 6.0 nm for all compositions prepared. The catalytic activity for ethanol electrooxidation in alkaline medium at room temperature (cyclic voltammetry and chronoamperometry results) showed that PtIr/C (70:30) and PtIr (90:10) exhibited higher performance toward ethanol oxidation than the other electrocatalysts. Experiments using direct ethanol alkaline fuel cell at 75 °C showed PtIr (90:10) as the best electrocatalyst and Ir/C as virtually inactive for ethanol oxidation in real conditions. The best result obtained using PtIr/C may be associated to the electronic effect between Pt and Ir that could decrease the poisoning on catalyst surface and also by the occurrence of bifunctional mechanism.
      PubDate: 2014-06-21
  • In Search of the Best Iron N       class="a-plus-plus">4-Macrocyclic Catalysts
           Adsorbed on Graphite Electrodes and on Multi-walled Carbon Nanotubes for
           the Oxidation of        type-small-caps">l-Cysteine by Adjusting the
           Fe(II)/(I) Formal Potential of the Complex
    • Abstract: Abstract The redox potential of macrocyclic complexes is a very predictive reactivity index for the electrocatalytic activity of these molecules, and it can be easily measured under the same conditions of the catalysis experiments. It reflects directly the activity of a given complex. We have investigated the effect of the Fe(II)/(I) formal potential on the catalytic activity of a series of Fe porphyrins and Fe phthalocyanines for the electrooxidation of l-cysteine, with the complexes directly adsorbed on ordinary pyrolytic graphite or adsorbed on multi-walled carbon nanotubes (MWCNTs) deposited on graphite. A correlation of log j (at constant potential) versus the Fe(II)/(I) formal potential of the catalysts gives a volcano curve for both systems without and with MWCNTs with higher activities in the latter case. Our results clearly show that the highest catalytic activity is achieved in a rather narrow potential window of Fe(II)/(I) formal potentials of N4-macrocyclic complexes. The use of MWCNTs as supporting material for the catalysts does not change the reactivity trends of the Fe complexes.
      PubDate: 2014-06-18
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