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Journal Cover Electrocatalysis
  [SJR: 0.817]   [H-I: 17]   [1 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1868-2529 - ISSN (Online) 1868-5994
   Published by Springer-Verlag Homepage  [2335 journals]
  • Glycerol Electrooxidation on Platinum-Tin Electrodeposited Films: Inducing
           Changes in Surface Composition by Cyclic Voltammetry
    • Authors: Gisele A. B. Mello; Pablo S. Fernández; María E. Martins; Giuseppe A. Camara
      Pages: 1 - 10
      Abstract: In this work, PtSn binary electrodeposits were prepared in three compositions and submitted to successive voltammetric cycles in presence of glycerol (1.0 mol L−1) in acidic media. Catalysts were characterized by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy before and after the cycles being performed, in order to check eventual changes in their compositions during the process. Spectroscopic results show that surface compositions are sensibly richer in Sn than their bulk counterparts. Overall, PtSn catalysts show a poor initial catalytic activity toward glycerol electrooxidation. However, as the cycles succeed, the voltammetric responses increasingly resemble that of Pt, while the oxidation currents increase. Results are rationalized in terms of a continuous enrichment of the surface by Pt at the expenses of a loss of Sn. Moreover, when the electrochemical surface area (ECSA) is estimated by stripping of CO, it becomes evident that electrooxidation currents remain growing, even when the ECSA is decreased, which makes the gain in catalytic activity particularly relevant. Ultimately, from a broader perspective, our results suggest that catalytic surfaces with tunable features (such as surface composition and catalytic response) can be obtained by the application of easily executable electrochemical protocols. Graphical ᅟ
      PubDate: 2017-01-01
      DOI: 10.1007/s12678-016-0332-z
      Issue No: Vol. 8, No. 1 (2017)
  • Effect of Acetic Acid on Carbon Monoxide Electrooxidation over Tin Oxide
           and Rhodium-Modified Platinum Electrode Materials
    • Authors: Layciane A. Soares; Fabiana L. S. Purgato; Claudia Morais; Teko W. Napporn; K. B. Kokoh; Paulo Olivi
      Pages: 11 - 15
      Abstract: The ethanol-to-CO2 conversion in a direct ethanol fuel cell application, which should theoretically exchange 12 electrons/molecule, leads mainly to acetic acid and, in a small amount, to carbon monoxide (CO) at the surface of Sn and Rh oxide-modified anode materials. According to the amount of these intermediate products, the reaction mechanism was found to be thoroughly modified. Therefore, investigations with cyclic voltammetric CO stripping combined with in situ infrared spectroscopy have aided to assess how the amount of produced acetic acid influenced CO electrooxidation using Pt/C, Pt80Rh20/C, Pt–SnO2/C, or Pt80Rh20–SnO2/C as electrode material. Based on the results, the adsorption of CO was hindered when the acetic acid concentration increased and the potential of the CO oxidation process shifted toward higher values. Graphical ᅟ
      PubDate: 2017-01-01
      DOI: 10.1007/s12678-016-0333-y
      Issue No: Vol. 8, No. 1 (2017)
  • Concurrent Deposition and Exfoliation of Nickel Hydroxide Nanoflakes Using
           Liquid Crystal Template and Their Activity for Urea Electrooxidation in
           Alkaline Medium
    • Authors: Mohamed A. Ghanem; Abdullah M. Al-Mayouf; Jai P. Singh; Prabhakarn Arunachalam
      Pages: 16 - 26
      Abstract: Nickel hydroxide nanoflakes (Ni(OH)2-NF) were prepared by chemical deposition and in situ exfoliation of nickel hydroxide layers confined in the aqueous domain of the liquid crystalline hexagonal template of Brij®78 surfactant. Using excess of sodium borohydride as a reducing agent generates concurrent excessive dynamic hydrogen bubbles which exfoliated and fragmented the nickel hydroxide layers precipitated within the soft hexagonal template. The physicochemical characterizations of Ni(OH)2-NF by using surface area analyser, X-ray diffraction (XRD), XPS and transmission electron microscope (TEM) showed the formation of α-Ni(OH)2 nanoflakes with thickness of 2–3 nm and have about 450 m2 g−1 surface area which is 20 times higher than that for bare nickel (bare-Ni) deposited without surfactant template. The electrocatalytic activity of the Ni(OH)2-NF catalyst for urea electrolysis was studied by cyclic voltammetry and chronoamperometry techniques. The Ni(OH)2-NF has shown a superior activity for the electrochemical oxidation of urea in alkaline solution and exhibits more than tenfold increase in activity in comparison with the bare-Ni deposit. The enhancement of urea electrooxidation activity was related to the superficial enhancement in the electroactive surface area of Ni(OH)2-NF. This new approach of deposition and in situ exfoliation by using liquid crystal template and hydrogen bubbles offers a new platform to nanostructuring wide range of catalysts with better catalytic performance. Graphical Nickel hydroxide nanoflakes (Ni(OH)2-NF) catalyst for the electrochemical oxidation of urea in alkaline solution.
      PubDate: 2017-01-01
      DOI: 10.1007/s12678-016-0336-8
      Issue No: Vol. 8, No. 1 (2017)
  • Facile One Pot Synthesis of CuO Nanostructures and Their Effect on
           Nonenzymatic Glucose Biosensing
    • Authors: Mohit Chawla; Veerender Sharma; Jaspreet Kaur Randhawa
      Pages: 27 - 35
      Abstract: Morphology of different CuO nanostructures is controlled by changing the precursor counterions. The CuO nanostructures were synthesized using three different precursor salts of copper namely acetate, nitrate, and sulfate via facile chemical precipitation route. The synthesized CuO nanostructures were thoroughly characterized using X-ray diffraction, optical spectroscopy, electron microscopy etc. The nanostructures were studied for catalytic nonenzymatic glucose sensing applications. CuO nanostructures synthesized from copper sulfate having flower-like morphology showed the highest glucose sensitivity of 1830 μAmM−1cm−2 in a linear range of 0.01–0.2 mM with a detection limit of 8 μM. Graphical Schematic illustrating the synthesis and glucose sensing experiments of CuO nanostructures.
      PubDate: 2017-01-01
      DOI: 10.1007/s12678-016-0337-7
      Issue No: Vol. 8, No. 1 (2017)
  • Systematic Study of Pt-Ru/C Catalysts Prepared by Chemical Deposition for
           Direct Methanol Fuel Cells
    • Authors: C. Jackson; O. Conrad; P. Levecque
      Abstract: In this research, the activity and stability for methanol electro-oxidation on Pt-Ru/C catalysts was increased by optimising the catalyst preparation method. The Pt-Ru/C catalysts were synthesised using Pt(acac)2 and Ru(acac)3 precursors for chemical deposition of the metals. Performance of the catalyst was examined by cyclic voltammetry and chronoamperometry in a methanol-containing electrolyte. TEM, EDS, X-ray photoelectron spectroscopy and XRD were used to physically characterise the catalysts. The parameters investigated were precursor decomposition phase, synthesis temperature and Pt/Ru ratio. Precursor deposition from the liquid phase was more active for methanol electro-oxidation, predominantly due to particle size and degree of alloying achieved during this precursor decomposition phase. Synthesis temperature affected the particle size, active surface area, ruthenium oxidation state and degree of alloying which in turn affected catalyst stability and activity for methanol electro-oxidation. The Pt/Ru ratio greatly affects the performance of the catalyst. The catalyst with the highest activity for methanol electro-oxidation was the catalyst synthesised at 350 °C with a Pt/Ru ratio of 50:50. Graphical
      PubDate: 2017-02-18
      DOI: 10.1007/s12678-017-0359-9
  • Conducting Polymer-Layered Carbon Nanotube as Sensor Interface for
           Electrochemical Detection of Dacarbazine In-Vitro
    • Authors: M. Satyanarayana; K. Yugender Goud; K. Koteshwara Reddy; K. Vengatajalabathy Gobi
      Abstract: A reusable electrochemical sensor ensembling carbon nanotubes and a conducting polymer together is fabricated for the detection of an important anti-cancer drug, dacarbazine (DTIC). A thin film of a conducting polymer, poly(2-amino-1,3,4-thiadiazole) (poly-ATD), is formed on the carbon nanotube paste electrode (CNPE) by employing a potentiodynamic polymerization technique. The fabricated sensor surface has been characterized by FTIR spectroscopy and scanning electron microscopy (SEM) for the structural and chemical properties of the electrode system. The electrochemical capability of the fabricated poly-ATD/CNPE composite electrode for the detection of DTIC is examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopic analysis (EIS), and the poly-ATD/CNPE electrode is found to be efficient for electrocatalytic oxidation of DTIC. Optimization and evaluation of the sensor system are examined by differential pulse voltammetry (DPV). A linear relationship of DTIC concentration over the peak current of DPVs is exhibited over a wide concentration range of 0.05–24.0 μM with a low detection limit (3σ/b) of 35 nM. Steady state current–time analysis experiments under hydrodynamic conditions exhibited a low detection limit of 20 nM, and the analysis time is as low as 10 s. Practical utility of the fabricated poly-ATD/CNPE biosensor for the detection of DTIC directly from artificial urine and pharmaceutical formulations has been demonstrated with very good recovery limits. Graphical
      PubDate: 2017-02-11
      DOI: 10.1007/s12678-017-0357-y
  • Design of Electrochemical Sensor Based on f MWCNT-CPE Decorated with Ti
           Nanofilm and Its Electrocatalytic Behavior Towards Aminotriazole
    • Authors: Imran Khan; Umar J Pandit; Sneha Wankar; Sudhir N Limaye
      Abstract: The present study is focused on the fabrication of electrochemical sensor based on electrochemically synthesized titanium nanoparticles (TiNPs) supported on multi-walled carbon nanotubes (MWCNTs) and its application in electrochemical quantification of aminotriazole. The designed electrochemical sensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The voltammetric results indicated that the combination of TiNPs and MWCNTs produced remarkable enhancement in electrocatalytic property towards the determination of aminotriazole. Various kinetic parameters like charge transfer resistance (Rct), apparent electron transfer rate constant (kapp), number of electrons transferred (n), electron transfer coefficient (α), formal redox potential (E0), standard heterogeneous rate constant (k0), surface coverage (Γ), diffusion coefficient (D), and catalytic rate constant (k) were evaluated. Based on the designed sensor, aminotriazole exhibited a linear correlation in the concentration range of 0.01–2.0 and 0.01–1.3 μg mL−1 with low detection limits of 0.166 and 0.267 ng mL−1 by AdLSV and DPAdSV, respectively. The fabricated sensor exhibited good accuracy, acceptable stability, and high efficacy for quantitative determination of aminotriazole in some real samples with notable recoveries ranging from 97.8 to 100.10%. Graphical Electrocatalytic oxidation of 3-amino-1,2,4-triazole at the modified surface of newly designed TiNP-fMWCNT-CPE to 3-amino-1,2,4-triazolinone via a two-electron electro-oxidation process.
      PubDate: 2017-02-09
      DOI: 10.1007/s12678-017-0358-x
  • Synergistic Ion Intercalations for High-Yield Synthesis of Li-Doped
           Graphene Nanosheets as an Efficient Electrocatalyst for Oxygen Reduction
    • Authors: Mohammad Zhiani; Fariborz Chitsazzadeh
      Abstract: A new electrochemical method for gram quantitative amount preparation of Li-doped graphene nanosheets was presented based on the one-pot cathodic exfoliation of a graphite electrode in an organic environment. Structural characterizations of synthesized graphene by FE-SEM and AFM indicate that graphene nanosheets have thickness lower than 4 nm, with a typical worm-like shape. Li-doped graphene nanoparticles show a superior electrocatalytic activity toward oxygen reduction reaction (ORR) without using any novel metals and losing stability during 3000 cycles. With a modification of the graphite configuration, the process can be used in a continuous manner, presenting a potentially scalable method for high-yield synthesis of few-layer graphene. Graphical Intercalation and de-intercalation of SDS and Li ions in graphite structure
      PubDate: 2017-02-04
      DOI: 10.1007/s12678-017-0352-3
  • Synthesis and Characterization of ZrO 2 /C as Electrocatalyst for Oxygen
           Reduction to H 2 O 2
    • Authors: Jussara F. Carneiro; Leandro C. Trevelin; Alex S. Lima; Gabriel N. Meloni; Mauro Bertotti; Peter Hammer; Rodnei Bertazzoli; Marcos R. V. Lanza
      Abstract: Electrogeneration of hydrogen peroxide (H2O2) has potential application in advanced oxidation processes. Amorphous carbon is well known as catalyst for oxygen reduction reaction (ORR) through two-electron pathway. However, modification of the carbon can improve its selectivity for the H2O2 electrogeneration. In the present study, we investigated the properties of ZrO2 nanoparticles supported on carbon black (Printex L6) as electrocatalyst for H2O2 production in acidic medium. The catalytic activity of ZrO2/C for oxygen reduction to H2O2 is higher than the catalytic activity of treated carbon black. The highest selectivity of the ZrO2/C catalyst for H2O2 production is attributable to the presence of oxygenated functional groups on its surface and consequently increase of the surface hydrophilicity in comparison with treated carbon black. This surface effect leads to highest H2O2 electrogeneration, which is shown as a high current efficiency (I(H2O2)%). In fact, increased H2O2 yields from 74.5 to 84.2% were observed for the treated carbon black and ZrO2/C catalysts, respectively, whereas the I(H2O2)% for the unmodified carbon black was 65.3%. Furthermore, the modification of carbon by ZrO2 nanoparticles shifted the ORR half-wave potential towards ca. 137 mV, indicating lower energy consumption for producing H2O2. Thus, the ZrO2/C nanoparticles are shown to be promising electrocatalysts for environmental applications. Graphical Zirconium oxides on carbon black improved significantly the selectivity of the substrate to H2O2 electrogeneration.
      PubDate: 2017-02-04
      DOI: 10.1007/s12678-017-0355-0
  • Local Impact of Pt Nanodeposits on Ionomer Decomposition in Polymer
           Electrolyte Membranes
    • Authors: S. Helmly; M. J. Eslamibidgoli; K. A. Friedrich; M. H. Eikerling
      Abstract: Based on recent theoretical studies, we designed a multistep experimental protocol to understand the impact of environmental conditions around Pt nanodeposits on membrane chemical degradation. The first experiment probes the local potential at a Pt microelectrode for different rates of permeation of hydrogen and oxygen gases from anode and cathode side. The subsequent degradation experiment utilizes the local conditions taken from the first experiment to analyze local rates of ionomer degradation. The rate of ionomer decomposition is significantly enhanced in the anodic H2-rich membrane region, which can be explained with the markedly increased amount of H2O2 formation at Pt nanodeposits in this region. Graphical Impact of Pt nanodeposits on chemical membrane degradation
      PubDate: 2017-02-02
      DOI: 10.1007/s12678-017-0353-2
  • Influence of Step and Island Edges on Local Adsorption Properties:
           Hydrogen Adsorption on Pt Monolayer Island Modified Ru(0001) Electrodes
    • Authors: Sung Sakong; Julia M. Fischer; David Mahlberg; R. Jürgen Behm; Axel Groß
      Abstract: The influence of steps and island edges on the local electronic structure of a (bi-)metallic single crystalline electrode surface and on the local, site-specific adsorption energy of adsorbed species, the so-called structural effects, was studied by periodic density functional theory based calculations, focusing on longer-range effects. Using hydrogen adsorption energies as a local probe, calculations were performed both for partly Pt monolayer covered planar Ru(0001) surfaces and for a stepped Ru( \(10\bar {19}\) ) surface decorated with a row of Pt atoms. The calculations demonstrate that the steps/island edges affect not only the nearest neighbor adsorption sites but also more distant ones with the extent depending on the particular structure. This longer-range effect is in excellent agreement with recent temperature-programmed desorption and spectroscopy experiments (Hartmann et al. Phys. Chem. Chem. Phys. 14, 10919, 2012). For the interaction of water molecules with partly Pt monolayer covered Ru(0001), similar trends as in the hydrogen adsorption have been found. In addition, hydrogen adsorption energies as a function of coverage have been used to derive the hydrogen coverage as a function of the electrode potential, exhibiting a broad range of stable hydrogen adsorption structures. Graphical Local adsorption properties of Pt monolayer island modified Ru(0001) electrodes are studied by first-principles calculations
      PubDate: 2017-01-30
      DOI: 10.1007/s12678-017-0354-1
  • Rate-Determining Factor of the Performance for Toluene
           Electrohydrogenation Electrolyzer
    • Authors: Kensaku Nagasawa; Yuki Sawaguchi; Akihiro Kato; Yoshinori Nishiki; Shigenori Mitsushima
      Abstract: The organic hydride of the toluene/methylcyclohexane (TL/MCH) system is one of the best energy carriers for renewable energies. In order to improve the energy conversion efficiency of the toluene hydrogenation process with water splitting, we have proposed the direct TL electrohydrogenation along with the water splitting process using an electrolyzer and have improved its performance. An analysis of the polarizations was essential for further improvement. In this study, the polarization properties of the anode (IrO2-based DSE®) and cathode (PtRu/C) were independently evaluated using a small electrolyzer equipped with a reversible hydrogen electrode (RHE). The cathode polarization was dominated by mass transfer above 100 mA cm−2. On the other hand, the anode polarization was dominated by a charge transfer process on the catalyst. Graphical Tafel plot for the anode (left) and cathode (right) with 10% TL at the operating temperatures from 40 to 80 °C in electrolyzer for direct electrohydrogenation of toluene with water decomposition.
      PubDate: 2017-01-26
      DOI: 10.1007/s12678-017-0351-4
  • Magnetically Induced Electrodeposition of Ni-Mo Alloy for Hydrogen
           Evolution Reaction
    • Authors: Sandhya Shetty; Ampar Chitharanjan Hegde
      Abstract: The electrocatalytic activity of Ni-Mo alloy coatings for hydrogen evolution reaction (HER) was tried to increase by inducing the magnetic field (B), perpendicular to the process of deposition. The electrocatalytic activity of Ni-Mo alloys were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) measurements in 1.0 M KOH medium. Ni-Mo alloy coatings developed at c.d. = 1.0 A dm−2 and B = 0.4 T was found to exhibit highest electrocatalytic activity for HER (with highest cathodic peak c.d. of −0.274 A cm−2 and least onset potential of −1.24 V and highest volume of H2 liberated, 14.0 mL), demonstrated by CV and CP experiments. The stability factor of Ni-Mo alloy coatings were evaluated through corrosion study. The experimental results showed that Ni-Mo alloy, electrodeposited in the presence of B, is more corrosion resistant than its conventional alloy, when tested in the same alkaline medium. The increase in the electrocatalytic activity of Ni-Mo alloy coatings, developed under induced B, is attributed to the structural and morphological changes, caused by an increase of Ni content in the alloy, evident from X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Graphical ᅟ
      PubDate: 2017-01-17
      DOI: 10.1007/s12678-017-0350-5
  • Understanding the Influence of the Biomass-Derived Alcohols on the
           Activity and Stability of Pt Nanoparticles Supported on Graphene
    • Authors: Rodrigo Teles; Ana Arenillas; Gabriel C. da Silva; Pablo S. Fernández; Eduardo S. F. Cardoso; Gilberto Maia; Cauê A. Martins
      Abstract: We produced Pt/GNRs by a one-step synthesis procedure and evaluated their electroactivity and stability towards glycerol electrooxidation reaction (GEOR) for the first time. We compared the electrocatalytic performance of GEOR with methanol and ethanol electrooxidation on Pt/GNRs at identical experimental conditions. The activities and stabilities for the electrooxidation of these biomass-derived alcohols on Pt/GNRs were compared to commercial Pt/C. The synthesis of the Pt/GNRs was confirmed by transmission electron microscopy, x-ray diffractometry, ultraviolet spectrophotometry, and Raman spectroscopy. We found that the activities of Pt/GNRs for these reactions are comparable to Pt/C, with improvement in terms of current density for methanol electrooxidation. Comparing potentiostatic measurements, we found that glycerol produces lower pseudo-stationary current densities than ethanol and methanol on both catalysts, with greatest values found for methanol electrooxidation on Pt/C. Otherwise, the GNRs remarkably enhance the stability of the catalyst for all the reactions, by increasing the stability of the current density during successive potential cycles, and by preventing the loss of electrochemically active surface area by avoiding carbon corrosion and Pt detachment. Moreover, we showed that the stability of the NPs depends on the biomass-derived alcohol used. The solution containing methanol reveals itself the most aggressive electrochemical environment to the catalyst, impacting in the decrease of surface area, while glycerol is less aggressive. Hence, the different products formed at the interface electrode/solution might lead to a different electrochemical environment, which plays an important role on the stability of the catalysts. Graphical ᅟ
      PubDate: 2017-01-07
      DOI: 10.1007/s12678-016-0349-3
  • Effect of Protonated Amine Molecules on the Oxygen Reduction Reaction on
           Metal-Nitrogen-Carbon-Based Catalysts
    • Authors: M. P. Karthikayini; Guanxiong Wang; P. A. Bhobe; Anjaiah Sheelam; Vijay K. Ramani; K. R. Priolkar; R. K. Raman
      Abstract: Non-precious metal electrocatalysts based on pyrolyzed metal, nitrogen, and carbon (MNC) are viewed as an inexpensive replacement for platinum-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. One of the enduring issues in the field of MNC catalysis is identifying the exact active structure responsible for the ORR. Many ORR active sites have been proposed recently, such as transition metal coordinated to (i) four pyrrolic nitrogens, (ii) four pyridinic nitrogens, and (iii) four pyridinic nitrogens interacting with one protonated nitrogen; among these, the latter is viewed as the most promising active site for the ORR. In this study, we have synthesized a manganese-based MNC catalyst (MnNx/C). EPR and X-ray absorption fine structure (XAFS) analysis indicated the presence of four nitrogens around the Mn(II) ion. The ORR performance of an MnNx/C catalyst was recorded in the presence of the disodium salt of ethylenediaminetetraacetic acid (EDTA-Na2), ethylene diamine (ED), and combination of ED and acetic acid (AA). The presence of EDTA-Na2 and ED + AA in the electrolyte solution maximizes the availability of protonated amine-N around the catalyst. As a consequence, we noticed significant improvement in the ORR kinetics in H2SO4 (10−4, 10−6 N) and NaOH (10−6 to 10−2 N) electrolyte solutions. The improvement in the onset potential for the ORR ranged between 80 and 160 mV as the pH was changed from 4 to 12. Based on XAFS data and ORR polarization in the presence of EDTA-Na2 and ED + AA, we believe that the MnN4 moiety interacting with the protonated amine is the most probable active site contributing to ORR activity in the H2SO4 (10−4, 10−6 N) and NaOH (10−6 to 10−2 N) electrolyte solutions. Graphical Hypothesized ORR active site in presence of the protonated amine.
      PubDate: 2016-11-17
      DOI: 10.1007/s12678-016-0341-y
  • Beneficial Promotion of Underpotentially Deposited Lead Adatoms on Gold
           Nanorods Toward Glucose Electrooxidation
    • Authors: Seydou Hebié; Teko W. Napporn; K. Boniface Kokoh
      Abstract: Unquestionably, obtaining nanomaterials with high catalytic activity requires the control of their size, shape, and composition since such parameters greatly influence the properties of the electrode surface. In this study, three gold nanorods (GNRs) with different aspect ratios and surface crystallographic orientations were synthesized by wet chemical method. Underpotential deposition (UPD) is an electrochemical technique used with lead adatoms for revealing the low-Miller-index Au(hkl) facets of the as-prepared nanorods. As catalyst effectiveness strongly depends on the nanoparticle surface and the nature of the electrolyte, lead adatom-modified Au electrode materials were made to catalyze the glucose oxidation in alkaline medium in which it is more reactive. It was found that the glucose-to-gluconolactone oxidation peak shifted of 50 mV toward lower potentials, indicating a surface energy gain of the anode material due to the UPDPb modification. Graphical ᅟ ᅟ
      PubDate: 2016-11-16
      DOI: 10.1007/s12678-016-0343-9
  • On the Effects of Ferricyanide as Cathodic Mediator on the Performance of
           Microbial Fuel Cells
    • Authors: Eduardo D. Penteado; Carmen Maria Fernandez-Marchante; Marcelo Zaiat; Ernesto Rafael Gonzalez; Manuel Andrés Rodrigo
      Abstract: This study provides an insight into the long-term influence of the use of ferricyanide in the cathode chamber of a microbial fuel cell (MFC) on the power generated and the COD removal attained. Two MFCs were operated in semicontinuous mode, using winery wastewater as fuel, activated sludge as the anodic inoculum, and concentrations of 0.05 and 0.25 M of ferrocyanide added in the cathode chamber as redox mediators. The MFC used had two chambers separated by a proton exchange membrane Sterion®. The results show that permeability of the membrane to mediators is a factor of the major significance. Under no crossover, the mediator produced a positive effect on the electricity generation and COD removal. However, as the experiments progressed, a significant concentration of mediator was detected in the anode chamber and the performance of the MFC gets worse. This work reports results that help to understand the main processes happening in the MFC. Highlights Crossover of ferrocyanide and ferricyanide to the anodic chamber reduces efficiency in the production of electricity The couple ferrocyanide/ferricyanide in the cathode chamber of an MFC can improve the performance in terms of COD removal and energy efficiency At low mediator concentration, a maximum in the power generation and COD removal can be attained At high mediator concentration, there was inhibition of biodegradation of winery wastewater Graphical abstract ᅟ ᅟ ᅟ
      PubDate: 2016-11-14
      DOI: 10.1007/s12678-016-0334-x
  • Pt Nanoparticles Supported on Niobium-Doped Tin Dioxide: Impact of the
           Support Morphology on Pt Utilization and Electrocatalytic Activity
    • Authors: Gwenn Cognard; Guillaume Ozouf; Christian Beauger; Ignacio Jiménez-Morales; Sara Cavaliere; Deborah Jones; Jacques Rozière; Marian Chatenet; Frédéric Maillard
      Abstract: Two synthesis routes were used to design high surface area niobium-doped tin dioxide (Nb-doped SnO2, NTO) nanostructures with either loose-tube (fibre-in-tube) morphology using electrospinning or aerogel morphology using a sol-gel process. A higher specific surface area but a lower apparent electrical conductivity was obtained on the NTO aerogel compared to the loose tubes. The NTO aerogels and loose tubes and two reference materials (undoped SnO2 aerogel and Vulcan XC72) were platinized with a single colloidal suspension and tested as oxygen reduction reaction (ORR) electrocatalysts for proton-exchange membrane fuel cell (PEMFC) applications. The specific surface area of the supports strongly influenced the mass fraction of deposited Pt nanoparticles (NPs) and their degree of agglomeration. The apparent electrical conductivity of the supports determined the electrochemically active surface area (ECSA) and the catalytic activity of the Pt NPs for the ORR. Based on these findings, electrospinning appears to be the preferred route to synthesize NTO supports for PEMFC cathode application. Graphical On top : SEM images of the synthesized supports : 5.0 at.% Nb-doped SnO2 aerogel (NTO-AG) and loose tubes (NTO-LT) - At the bottom : specific activity (SA0.90) and mass activity (MA0.90) of the synthesized electrocatalysts for the oxygen reduction reaction (ORR) determined at E = 0.90 V vs. RHE as a function of the conductivity of the supports
      PubDate: 2016-11-10
      DOI: 10.1007/s12678-016-0340-z
  • The Oxygen Reduction Reaction on Kinked Stepped Surfaces of Pt
    • Authors: Fumiya Sugimura; Masashi Nakamura; Nagahiro Hoshi
      Abstract: The oxygen reduction reaction (ORR) has been studied on kinked stepped surfaces of Pt inside the stereographic triangle with the use of rotating disk electrode (RDE) in 0.1 M HClO4. The kinked stepped surfaces are composed of (331) = 3(111)-(111) structure of which step line contains (100) kink: 3(111) − [m(111) + (100)], where m denotes the number of straight step atoms. The activity for the ORR decreases with increasing the kink atom density d k of the surface with m = 1, 3, 6, and 21, whereas the surface with m = 11 has specifically high activity for the ORR. The activity on Pt(16 15 5) = 3(111) − [11(111)-(100)] exceeds that of Pt(331) that gives the highest activity in stepped surfaces. The electricity of Pt oxide formation on Pt(16 15 5) m = 11 is the lowest in the kinked stepped surfaces examined. Graphical Kinked-stepped surface of Pt enhancing the activity for the oxygen reduction reaction (ORR), and the correlation between the ORR activity and Pt oxides
      PubDate: 2016-11-03
      DOI: 10.1007/s12678-016-0339-5
  • An Investigation of a Polydopamine-Graphene Oxide Composite as a Support
           for an Anode Fuel Cell Catalyst
    • Abstract: Home-made graphene oxide (GO) with a high surface area was functionalized by polydopamine (PDA) and was labeled PDA-GO, while GO without PDA was labeled as GO. With different compositions of metals (Pt and/or Pd), the electrodeposition of the metals onto the prepared GO and PDA-GO supports was prepared for the anode electrocatalyst. The electrocatalytic activities of the electrocatalysts (xPtPd/GO and xPtPd/PDA-GO, where x = 1–5) were studied in the oxidation of alcohols (e.g., methanol and ethanol). Morphologies obtained from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images showed that the as-prepared GO and PDA-GO supports can accommodate electrodeposited metals loaded on the topmost layer of the support surfaces, although the size of nanoparticles is somewhat different. The electrochemical results indicated that the xPtPd/PDA-GO catalysts offered outstanding oxidation efficiencies. The prepared 5PtPd/PDA-GO catalyst provided enhanced activity and long-time stability in the oxidation reactions. The GO surface modified by the polymer and the other electrodeposited metal catalysts provided a larger number of available active sites, as the PDA offered a greater electric connection between the metal catalysts and the GO support during alcohol oxidation. Graphical Optimising ECL Production Through Careful Selection of Co-Reactions Based on Energetics Involved
      PubDate: 2016-11-02
      DOI: 10.1007/s12678-016-0338-6
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