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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
  • A Simulation Study of Pt Particle Degradation During Potential Cycling
           Using a Dissolution/Deposition Model
    • Abstract: Abstract Polymer electrolyte fuel cells suffer from reduced lifetimes due to degradation of their Pt catalysts during operation. To understand the fundamental process of the Pt degradation, we proposed a model for the Pt particle growth based on the Gibbs-Thomson equation, which asserts that smaller particles tend to be dissolved in preference to the larger ones. We simulated the particle distribution changes during rectangular potential cycling between 0.6 and 1.0 V vs. the reversible hydrogen electrode at 25 °C under a N2 atmosphere. The parameters in our model were determined by fitting to the experimental data. The calculation results and experimental data for the changes in the particle distribution and electrochemically active surface area were in good agreement. Additionally, the particle distribution change under different conditions such as the potential range and the initial particle size distribution could be simulated by changing the parameters in the model. When the initial size standard deviation is low, particle growth does not readily occur because the differences in the particle size are small. When the initial standard deviation in the particle size is large, the particle growth is accelerated by the large difference in the particle sizes, because small particles more readily dissolve. Finally, the particle distribution becomes stable and the degradation levels off. It was suggested that the particle growth could be anticipated by using our model.
      PubDate: 2014-09-14
  • Insight into the Photocatalytical Activity of TiO       class="a-plus-plus">2 Nanoparticles Through the
           Electrochemical Characterization of Carbon Paste Electrodes
    • Abstract: Abstract We propose a methodology to study the behavior of semiconductor nanoparticles—especially TiO2 nanoparticles—in photoactivated processes via electrochemical studies, using solid electrodes instead of thin-film electrodes. This strategy allows the comparison of properties probed from freestanding nanoparticles with the results of electrochemical characterization, without grain growth or texturization effects, frequently observed in thin-film electrodes. In this study, solid electrodes prepared with homogenized carbon paste and TiO2 were characterized. The TiO2/carbon paste electrode showed lower currents than the carbon paste electrode under UVC illumination. The electrode containing 15 % TiO2/carbon paste showed better results for electroanalytical characterization. However, for electrolysis, the carbon paste electrode with 60 % TiO2 was used, as 15 to 45 % (w/w) TiO2 content was deemed insufficient for this purpose. In order to compare the electrochemical characterization with photocatalytical properties, the degradation of rhodamine B (Rhod-B) dye was used. The reaction order for the Rhod-B degradation was between first and second order, which suggests that the products of the reaction may interfere with the decomposition itself. The results will enhance the establishment of a valuable characterization route to support future research regarding the influence of different materials in photodegradation processes.
      PubDate: 2014-08-28
  • Enhanced Electrooxidation of Ethanol Using Pd/C + TiO       class="a-plus-plus">2 Electrocatalysts in
           Alkaline Media
    • Abstract: Abstract This work describes the use of Pd nanoparticles synthetized by the borohydride process and supported on physical mixtures of C + TiO2 toward the ethanol electrooxidation reaction in alkaline media. In this study, the C/TiO2 ratios were studied by ranging the mass proportions of C/TiO2—100:0, 80:20, 60:40, 40:60, 20:80, and 0:100. X-ray diffraction patterns showed the presence of Pd face-centered cubic (fcc) structure, and carbon and TiO2 in rutile and anatase phases. Transmission electron micrographs showed metal nanoparticles with average particle size between 5.5 and 7.2 nm for all electrocatalysts. Cyclic voltammograms of Pd/C + TiO2 electrocatalysts showed a decrease of Pd surface area with the TiO2 increasing, while the linear sweep and chronoamperometric results showed the Pd/C + TiO2 (40:60) as the most promising electrocatalyst toward ethanol electrooxidation. The best results obtained with this catalyst were attributed to the presence of carbon and TiO2 in intermediate proportions since TiO2 supplies OH species and also changes the Pd d-band by a strong metal support interaction, increasing the alcohol oxidation without a significant decrease of conductivity and surface area.
      PubDate: 2014-08-22
  • Reactivity of Alcohols with Three-Carbon Atom Chain on Pt in Acidic Medium
    • Abstract: Abstract n-Propanol, 2-propanol, 1,2-propanediol, 1,3-propanediol, and glycerol are all saturated alcohols with a three-carbon atom chain. The difference between them is the number of hydroxyl groups and their positions in these molecules. The interaction between alcohols with a three-carbon atom chain and model surfaces and the further reaction have been widely investigated in the last three decades. In this short review, we will concentrate our attention on the reactivity of n-propanol, 2-propanol, 1,2-propanediol, 1,3-propanediol, and glycerol on smooth Pt in acidic medium. We will present the most important results reported in the literature in this field, highlighting the main particularities related to their reactions, addressing key points such as the impact of the position of the OH group in the molecule, number of OH groups in the molecule, and presence of vicinal OH groups in the molecule on the reactivity of these alcohols over Pt. Finally, we will present some perspectives concerning the application of alcohols with a three-carbon atom chain, mainly glycerol, in fuel cells.
      PubDate: 2014-08-21
  • Oxygen Electroreduction on Electrodeposited PdAu Nanoalloys
    • Abstract: Abstract The electrocatalytic activity of electrodeposited palladium–gold (PdAu) alloys towards the oxygen reduction reaction (ORR) was studied in 0.05 M H2SO4 and 0.1 M KOH solutions using the rotating disc electrode (RDE) method. The electrochemical deposition was carried out at a constant potential and the ratio of concentrations of the precursors in the deposition bath was varied. The surface morphology of the deposits was studied using scanning electron microscopy (SEM), and the average particle size for PdAu alloys was determined to be about 6 nm. The X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) studies suggest that the resulting PdAu coatings are alloyed. The ORR activities of the electrodes were compared by calculating the specific activities on the basis of the real electroactive surface area of Pd. The specific activity did not depend on the composition of the alloy in sulphuric acid solution, but in alkaline medium it increased with decreasing Pd content.
      PubDate: 2014-08-20
  • 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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