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Journal Cover Electrocatalysis
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1868-2529 - ISSN (Online) 1868-5994
     Published by Springer-Verlag Homepage  [2209 journals]   [SJR: 0.542]   [H-I: 7]
  • Fabrication of Nanostructured Palladium Within Tridentate
           Schiff-Base-Ligand Coordination Architecture: Enhancement of
           Electrocatalytic Activity Toward CO       class="a-plus-plus">2 Electroreduction
    • PubDate: 2014-05-22
  • Non-precious Metal Oxygen Reduction Reaction Catalysts Synthesized Via
    • 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: 2014-05-21
  • Photoelectrocatalytic Degradation of Ofloxacin Using Highly Ordered
           TiO2 Nanotube Arrays
    • 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: 2014-05-09
  • 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: 2014-05-09
  • 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: 2014-04-30
  • 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: 2014-04-27
  • Heterogenization of a Water-Insoluble Molecular Complex for Catalysis of
           the Proton-Reduction Reaction in Highly Acidic Aqueous Solutions
    • PubDate: 2014-04-26
  • 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: 2014-04-26
  • 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: 2014-04-08
  • 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: 2014-04-06
  • Direct Dimethyl Ether Fuel Cell with Much Improved Performance
    • Abstract: Abstract Due to several apparent advantages over methanol, dimethyl ether (DME) has been viewed as a promising alternative fuel for direct fuel cell technology. Similar to methanol, DME oxidation requires a surface oxidant, such as OH, for the removal of adsorbed CO. Consequently, the reaction occurs at much faster rates on binary PtRu catalysts than Pt alone. In this work, PtRu catalysts with a wide variety of Pt-to-Ru ratios were systematically studied in the direct DME fuel cell (DDMEFC) operating at 80 °C. A Pt50Ru50 catalyst was found to perform the best at high and middle voltages, while a Pt80Ru20 catalyst performed best at low voltages. DDMEFC operation conditions, such as DME flow rate, anode back pressure, DME-to-water molar ratio, and membrane thickness, were also studied in order to maximize the cell performance. A maximum power density of 0.12 W cm−2 obtained in this work exceeds the highest reported DME performance. In comparison with the direct methanol fuel cell (DMFC), the optimized DDMEFC performs better at cell voltages higher than 0.55 and 0.49 V with feed concentrations of methanol of 0.5 and 1.0 M, respectively.
      PubDate: 2014-04-04
  • Understanding Catalyst Layer Degradation in PEM Fuel Cell Through
           Polarization Curve Fitting
    • PubDate: 2014-04-04
  • New Electrocatalysts with Pyrolyzed Siloxane Matrix
    • Abstract: Abstract In a first screening, platinum nanoparticles in pyrolyzed siloxane matrices with additional carbon fillers were developed and tested for their use as electrocatalysts. The influence of various parameters - type of carbon filler, carbon content, pyrolysis temperature, and siloxane composition - on structural properties and on electrochemical activity was investigated. Homogeneous distributions of platinum nanoparticles could be obtained for most of these electrocatalysts. Uniform platinum particles were generated with average particle sizes of 2.5–4.7 nm. At a temperature of 300 °C, the siloxane-based electrocatalysts exhibit high thermal stabilities with maximum weight losses of around 8 wt% after 20 h. The electrochemical behavior of the siloxane-based electrocatalysts in contact with 0.1 M H2SO4 was studied by cyclic voltammetry. Electrocatalytic activities were studied by CO adlayer oxidation, which also served for determining the electrochemical active surface area. High electrochemically active surface areas with up to 50 m2 g−1 Pt were obtained, which are in the same range as carbon-based electrocatalysts. Interestingly, some siloxane-based electrocatalysts showed a slightly higher catalytic activity for CO adlayer oxidation than carbon-based materials.
      PubDate: 2014-04-03
  • Addendum to Immobilization-Enabled Proton-Reduction Catalysis by a Di-iron
           Hydrogenase Mimic
    • PubDate: 2014-04-01
  • Effect of TiO2
           Content on Ethanol Electrooxidation in Alkaline Media Using Pt
           Nanoparticles Supported on Physical Mixtures of Carbon and TiO       class="a-plus-plus">2 as Electrocatalysts
    • Abstract: Abstract Pt nanoparticles supported on physical mixtures of carbon and TiO2 (Pt/(C + TiO2) electrocatalyst) were tested for ethanol electrooxidation in alkaline media. The electrocatalysts were prepared with different C/TiO2 mass ratios using borohydride as reducing agent. X-ray diffraction patterns of the obtained materials showed the peak characteristic of Pt face-centered cubic (fcc) structure, carbon, and TiO2 phases. Transmission electron micrographs showed metal nanoparticles distributed preferentially over TiO2 support with average particle size between 5 and 7 nm for all electrocatalysts. The cyclic voltammograms of Pt/(C + TiO2) electrocatalysts in alkaline media showed a decrease of Pt surface area with the increase of TiO2 content. The electrooxidation of ethanol suggests the Pt/(C + TiO2) (40:60) as the most promising electrocatalyst for use in fuel cells since it presents almost the same current density value as that of the others and also slower current density decay in chronoamperometry. Moreover, TiO2 provides oxygen species to promote the CO oxidation, resulting in more activity.
      PubDate: 2014-01-24
  • Agglomeration and Cleaning of Carbon Supported Palladium Nanoparticles in
           Electrochemical Environment
    • Abstract: Abstract Here we investigate the electrochemical behavior of Pd/C synthesized by reduction with ethylene glycol in the presence of polyvinylpyrrolidone (EG-PVP). EG-PVP produces nanoparticles (NPs) with a narrow size distribution, but some of them remain covered by impurities after the synthesis. After successive voltammetric cycles, NPs become cleaner, but some agglomeration and structural modification occur; these effects affect the electrochemical behavior of Pd/C in different ways, so we used CO as a probe to better understand the processes taking place. CO stripping shows that the general features of the multiple oxidation peaks change with the number of cycles. Possibly, CO and OH from different NPs react when the particles agglomerate, contributing to CO stripping changes. Finally, different active areas are found when the charges involved in CO oxidation and PdO reduction are compared. Such differences are rationalized in terms of a balance between the increase of sites which promote the oxidation of CO and the loss of area provoked by the growing of the particles. Figure After successive voltammetric cycles, Pd/C NPs become cleaner with slightly agglomeration, which lead to increase of the electrochemically active surface area. The value of area reaches a maximum, after this point the agglomeration is the main effect and contributes to the surface area decay. The agglomeration facilitates the CO electrooxidation reaction among NPs
      PubDate: 2014-01-16
  • Electrochemical and In Situ FTIR Study of        class="a-plus-plus">o-Cresol on Platinum Electrode
           in Acid Medium
    • Abstract: Abstract The electrochemical behaviour of o-cresol in acidic medium on platinum electrode has been studied by cyclic voltammetry and in situ Fourier transform infrared spectroscopy. The o-cresol suffers hydrolysis during oxidation giving rise to the formation of methyl-p-benzoquinone. In situ FTIR spectroscopic studies also reveal the presence of CO2, formed as a consequence of the rupture of the aromatic ring. Moreover, the oxidation of o-cresol in acidic medium produces a polymeric film on the platinum surface that precludes further oxidation of o-cresol. The reduction of o-cresol at potentials below 0 V produces in the first step the partial reduction of the aromatic ring and when the potential goes to values below 0 V, methyl-cyclohexanone.
      PubDate: 2014-01-10
  • The Role of Electrodeposited Pd Catalyst Loading on the Mechanisms of
           Formic Acid Electro-Oxidation
    • Abstract: Abstract This work addresses the effects of Pd nanoparticle loading and dispersion on the mechanisms of formic acid (FA) electro-oxidation. For this purpose, different levels of Pd nanoparticle loading (0.10–0.98 mg cm−2) with similar size (∼10–13 nm) were electrodeposited on the carbon cloth via square wave pulse technique. The mechanisms of FA oxidation in 0.5 M HCOOH + 0.5 M H2SO4 solution were studied and identified using cyclic voltammetry (CV) together with Fourier transform infrared spectroscopy (FTIR). Based on the obtained results, it was found that the electrochemical active surface area and Tafel slopes are independent of Pd loading levels, but both the shape and peak potential of the voltammograms are significantly affected by the Pd loading levels. The results of CV and FTIR showed that the different levels of Pd loading changes the FA oxidation pathway, which is attributed to the fact that the higher Pd loading results in the closer distribution of Pd nanoparticles. It was suggested that, at high Pd loading, the Pd-HCOOads formation is not the only available pathway for FA oxidation process and the Pd-COads formation pathway also exists, which is oxidized to CO2 at more anodic potentials.
      PubDate: 2014-01-10
  • Molecular Modeling of Hydronium Ion and Water Distribution in Water-Filled
           Pt Nanochannels with Corrugated Walls
    • Abstract: Abstract Classical molecular dynamics was employed to study the impact of nanoconfinement and surface nanostructure on electrostatic phenomena and transport properties in catalyst layer pores of polymer electrolyte fuel cells. The porous structure of an ionomer-free ultrathin catalyst layer was represented by a water-filled nanochannel with corrugated and negatively charged Pt walls. The equilibrium hydronium ion distribution in the channel was used to assess local reaction conditions. We rationalized the effects of nanostructuring and metal surface charge on the electrostatic effectiveness factor of the channel. Furthermore, we investigated the water dynamics in the nanochannel, calculating the self-diffusion coefficients of surface and bulk-like water.
      PubDate: 2013-12-11
  • Lactose Electrooxidation on the Nickel Oxide Nanoparticles Electrocatalyst
           Prepared on the Multi-walled Carbon Nanotubes Modified Electrode
    • Abstract: Abstract The preparation of multi-walled carbon nanotubes–NiO nanoparticles composites (MWCNT–NiO) is presented and the composites were used for modification of glassy carbon electrode for lactose electrooxidation in NaOH. Nickel oxide (NiO) was accumulated on multi-walled carbon nanotubes (MWCNT) by pulsed potential electrodeposition. The structure and nature of the MWCNT–NiO were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that NiO nanoparticles were homogeneously electrodeposited on the surfaces of MWCNTs. Also, the electrochemical behaviour of MWCNT–NiO nanoparticles composite in an aqueous solution of alkaline of lactose was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The peak on the voltammogram for MWCNT–NiO composite electrode in alkaline solutions of lactose was observed which was ascribed to the lactose oxidation in alkaline medium. The results obtained are discussed from the point of view of employment of the MWCNT–NiO composites for the catalytic electrodes of sugar-oxygen fuel cells.
      PubDate: 2013-12-07
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