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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  [2341 journals]
  • Magnetically Induced Electrodeposition of Ni-Mo Alloy for Hydrogen
           Evolution Reaction
    • Authors: Sandhya Shetty; Ampar Chitharanjan Hegde
      Pages: 179 - 188
      Abstract: 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 Abstract ᅟ
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0350-5
      Issue No: Vol. 8, No. 3 (2017)
       
  • 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
      Pages: 189 - 195
      Abstract: 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 Abstract Zirconium oxides on carbon black improved significantly the selectivity of the substrate to H2O2 electrogeneration.
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0355-0
      Issue No: Vol. 8, No. 3 (2017)
       
  • 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
      Pages: 196 - 213
      Abstract: 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 Abstract 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: 2017-05-01
      DOI: 10.1007/s12678-017-0358-x
      Issue No: Vol. 8, No. 3 (2017)
       
  • 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
      Pages: 214 - 223
      Abstract: 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 Abstract
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0357-y
      Issue No: Vol. 8, No. 3 (2017)
       
  • Systematic Study of Pt-Ru/C Catalysts Prepared by Chemical Deposition for
           Direct Methanol Fuel Cells
    • Authors: C. Jackson; O. Conrad; P. Levecque
      Pages: 224 - 234
      Abstract: 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 Abstract
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0359-9
      Issue No: Vol. 8, No. 3 (2017)
       
  • Impedance Measurement and Selection of Electrochemical Equivalent Circuit
           of a Working PEM Fuel Cell Cathode
    • Authors: Kazimierz Darowicki; Lukasz Gawel
      Pages: 235 - 244
      Abstract: Abstract The dynamic impedance analysis of direct methanol fuel cell (DMFC) cathode supplied with pure oxygen is presented. Presented results were obtained during dynamic changes of the current density in working fuel cell. Investigation of the occurring processes at cathode was carried with dynamic electrochemical impedance spectroscopy (DEIS). A discussion was conducted based on the determined correlation parameter χ 2. It was shown that the selection of an appropriate equivalent circuit cannot be carried out only with correlation parameter of analysis between experimental impedance spectra and the equivalent circuit. Comprehensive analysis of equivalent circuit parameter changes during fuel cell working is needed to determine appropriate equivalent model. Thanks to DEIS technique, comparing of the different equivalent circuits proposed in other works during dynamic changes of operating condition could be presented. In addition, the new electrical circuit has been proposed to describe the cathode performance with poisoned electrocatalyst in fuel cell with reduced efficiency. Graphical Abstract The equivalent electrical circuit of an operating fuel cell cathode
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0363-0
      Issue No: Vol. 8, No. 3 (2017)
       
  • PtRu Nanoparticles Supported on Phosphorous-Doped Carbon as
           Electrocatalysts for Methanol Electro-Oxidation
    • Authors: Viviane Santos Pereira; Julio C. M. da Silva; Almir Oliveira Neto; Estevam V. Spinacé
      Pages: 245 - 251
      Abstract: Abstract P-doped carbon was prepared by thermal treatment of commercial carbon Vulcan XC72 with H3PO4 at 800 °C. PtRu nanoparticles were supported on carbon Vulcan XC72 (C) and on P-doped carbon (P-C) using an alcohol reduction process. The obtained materials were characterized by energy-dispersive X-ray spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and cyclic voltammetry. The performance of the electrocatalyst was evaluated for methanol electro-oxidation. The intensities of D-band and G-band of Raman spectra were different for P-doped carbon and carbon Vulcan XC72. X-ray diffraction of PtRu/C electrocatalyst showed that Pt face-centered cubic phase and Ru amorphous phase coexist in this material, while for PtRu/P-C electrocatalyst, it was observed the presence of PtRu alloy and Ru hexagonal close-packed phases. The use of P-doped carbon as support for PtRu nanoparticles improves the methanol electro-oxidation. This increase of activity could be attributed to a decrease of average nanoparticle sizes and/or more active Pt and Ru species resulting from metal-support interactions. Graphical Abstract
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0360-3
      Issue No: Vol. 8, No. 3 (2017)
       
  • Enhancement of Ethanol Oxidation Reaction on Pt (PtSn)-Activated Nickel
           Foam Through In situ Formation of Nickel Oxy-Hydroxide Layer
    • Authors: Boguslaw Pierozynski; Tomasz Mikolajczyk
      Pages: 252 - 260
      Abstract: Abstract The present paper reports on a significant enhancement of ethanol oxidation reaction (EOR), investigated on Pt and PtSn-modified nickel foam electrodes, realized via in situ formation of surface nickel oxy-hydroxide layer in 0.1 M NaOH solution. In the presence of ethanol in electrolyte, adsorbed C2H5OH molecules (and/or its oxidation intermediates) prevent Pt (PtSn) sites from their extensive dissolution upon prolonged surface electrooxidation of Ni foam electrode. The above was elucidated through cyclic voltammetry examinations and a.c. impedance-derived charge transfer resistance parameter values. Surface topography and the presence of catalytic additives were revealed from the combined scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) analyses. Graphical Abstract Enhanced EOR kinetics on electrooxidized Pt/PtSn Ni foam. Surface-adsorbed ethanol/oxidation intermediates prevent Pt/PtSn catalyst sites. Pt/PtSn-modified Ni foam—introductory anode for alkaline direct ethanol fuel cell.
      PubDate: 2017-05-01
      DOI: 10.1007/s12678-017-0362-1
      Issue No: Vol. 8, No. 3 (2017)
       
  • Acetylene-Treated Titania Nanotube Arrays (TNAs) as Support for Oxygen
           Reduction Reaction (ORR) Platinum Thin Film Catalysts
    • Abstract: Abstract Platinum layers show higher specific oxygen reduction reaction (ORR) activities than nanoparticles, and smooth monolayers of platinum on polycrystalline gold have been achieved by electrodeposition from CO-saturated solutions. Since Pt monolayers are interesting catalytic systems, this methodology was attempted on acetylene-treated titania nanotubes (TNAs) with high conductivity. However, the investigation of the as-treated TNAs found that probably nanotubes with an oxygen-containing graphitic overlayer were formed. It was observed that deposition after partial oxidative removal of the overlayer led to very low ORR activities while deposition on the intact overlayer gave rise to the highest activities obtained in our research so far. This is attributed to a “tie-layer” effect, in which the carbon layer screens the negative effects of the underlying TiO2 layer. The interesting effects of the graphitic overlayer on the ORR activity of the Pt deposits on acetylene-treated TNAs offer a strategy to mitigate the unfavorable interactions of the Pt/TiO2 interface. However, the carbon layer in this study was found not to be stable upon potential cycling. Graphical Abstract Only Gold Lets Platinum be Platinum: Monolayer amounts of Pt, electrodeposited under CO termination, so far, only show specific activities comparable to polycrystalline platinum if deposited on polycrystalline gold. TiO2 modifications as supports facilitate higher activities only at enhanced conductivities, which usually sacrifice their stability.
      PubDate: 2017-04-17
       
  • New Platinum Alloy Catalysts for Oxygen Electroreduction Based on Alkaline
           Earth Metals
    • Abstract: Abstract The energy efficiency of polymer electrolyte membrane fuel cells is mainly limited by overpotentials related to the oxygen reduction reaction (ORR). In this paper, we present new platinum alloys which are active for the ORR and based on alloying Pt with very abundant elements, such as Ca. Theoretical calculations suggested that Pt5Ca and Pt5Sr should be active for the ORR. Electrochemical measurements show that the activity of sputter-cleaned polycrystalline Pt5Ca and Pt5Sr electrodes is enhanced by a factor of 5–7 relative to polycrystalline Pt. Accelerated stability testing shows that after 10,000 electrochemical cycles, the alloys still retain over half their activity. The stability is thus not quite on par with the similar Pt-lanthanide alloys, possibly due to the somewhat lower heat of formation. Graphical Abstract Left: The structure of Pt5Ca with a compressed Pt overlayer. The compression increases activity for the Oxygen Reduction Reaction (ORR). Right: The measured ORR activity of the best Platinum alloys.
      PubDate: 2017-04-17
       
  • Carbon Modified with Vanadium Nanoparticles for Hydrogen Peroxide
           Electrogeneration
    • Authors: P. S. Simas; V. S. Antonin; L. S. Parreira; P. Hammer; F. L. Silva; M. S. Kronka; R. B. Valim; M. R. V. Lanza; M. C. Santos
      Abstract: Abstract This paper compares the results of two preparation routes for the production of carbon (Vulcan XC 72R) modified with vanadium nanostructured electrocatalysts for hydrogen peroxide (H2O2) electrogeneration using the following mass proportions of vanadium on carbon (V/C): 1, 3, 5, 7, 10, and 13%. Best results for H2O2 electrogeneration were obtained using a V/C sol-gel method (SGM) with 3%, highest ring currents. For oxygen reduction reaction (ORR), using the V/C SGM with 3% and V/C polymeric precursor method (PPM) with 7%, the results of ring currents measured are very high when compared to Vulcan XC 72R. X-ray diffraction (XRD) analysis mainly showed the V2O5 phase. X-ray photoelectron spectroscopy (XPS) results of the V/C PPM 7% and V/C SGM 3% samples highlight the predominance of the V2O5 phase and, for the latter catalyst, a more oxidized carbon surface. For the most promising electrocatalysts, the contact angle was evaluated, showing that the anchoring of the metal in the carbon surface increases the hydrophilicity of the materials. The prepared materials are promising for peroxide electrogeneration mainly due to the synergetic effect of vanadium oxide nanoparticles and acid oxygen species of the carbon, contributing to enhancing catalyst hydrophilicity. Graphical Abstract Electrocatalytic activity toward peroxide electrogeneration using V/C electrodes
      PubDate: 2017-04-11
      DOI: 10.1007/s12678-017-0366-x
       
  • Catalytic Duality of Platinum Surface Oxides in the Oxygen Reduction and
           Hydrogen Oxidation Reactions
    • Authors: Sadaf Tahmasebi; Ashley A. McMath; Julia van Drunen; Gregory Jerkiewicz
      Abstract: Abstract In polymer electrolyte membrane fuel cells (PEMFCs), the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) take place on the surface of platinum nanoparticles (Pt-NPs) residing on carbon support. Polycrystalline platinum (Pt(poly)) serves as a model polyoriented system due to its randomly oriented grains separated by grain boundaries, and research using Pt(poly) creates important background knowledge that is used to identify and understand electrochemical phenomena occurring in fuel cells. In this study, we report new results on the electrochemical behavior of Pt(poly) in 0.50 M H2SO4 aqueous solution saturated with reactive gases, namely O2(g) and H2(g). We analyze the influence of the potential scan rate over a broad range of values (1.00–50.0 mV s−1) on the cyclic voltammetry (CV) behavior of Pt(poly). A comparative analysis of the impact of dissolved O2 and H2 on the electrochemical behavior of Pt(poly) is performed using CV profiles and capacitance transients. Their analysis reveals the existence of new features that are observed in the potential range corresponding to the Pt surface oxide formation and reduction. The results indicate that the Pt surface oxide reveals catalytic duality because it acts both as an inhibitor and a catalyst in both the ORR and HOR. In the case of the ORR, the anodic-going transients reveal that the process becomes inhibited as the Pt surface oxide develops, while in the cathodic-going transients, the reduction of Pt surface oxide significantly (ca. 65%) increases the reaction rate. In the case of the HOR, the anodic-going transients also reveal that the process becomes inhibited as the Pt surface oxide develops, while in the cathodic-going transients, the reduction of Pt surface oxide increases (ca. 15%) the reaction rate. The catalytic effect can be attributed either to changes in the surface electronic structure that accompanies the surface oxide reduction or to short-lived increase in the electrochemically active surface area. Graphical Abstract ᅟ
      PubDate: 2017-04-06
      DOI: 10.1007/s12678-017-0372-z
       
  • Electrospun Carbon Nanofibers as Supports for Bioelectrodes
    • Authors: Cenk Gumeci; Duyen Do; Scott Calabrese Barton
      Abstract: Abstract A wide range of carbon nanofiber (CNF) mats with controlled properties of fiber diameter, surface area, porosity, and conductivity were fabricated via a facile and economical electrospinning method. CNFs are used as supports for bioelectrodes to enhance enzyme utilization. This study employed glucose oxidase (GOx) in a redox hydrogel system, which mediates electron transfer via osmium metal center, to create a glucose bioelectrode. CNFs reduces the hydrogel thickness and enhances the electron transport. CNFs exhibit promising glucose oxidation current density reaching 10 mA cm−2 that is higher than those of commercial carbon materials such as multiwalled carbon nanotubes (MWCNT), Bucky paper, Pyrograf, and Toray paper. Graphical Abstract ᅟ
      PubDate: 2017-03-30
      DOI: 10.1007/s12678-017-0373-y
       
  • Methanol Oxidation on Pt(111) from First-Principles in Heterogeneous and
           Electrocatalysis
    • Authors: Sung Sakong; Axel Groß
      Abstract: Abstract The catalytic oxidation of methanol on Pt(111) has been addressed based on first-principles electronic structure calculations. The chemical environment corresponding to the conditions in heterogeneous and electro-catalysis has been taken into account in a grand-canonical approach. Furthermore, the aqueous electrolyte in electrocatalysis has been described in an implicit solvent model. Thus, we find characteristic differences between the methanol oxidation paths in heterogeneous and electro-catalysis. The presence of the aqueous electrolyte stabilizes reaction intermediates containing hydrophilic groups thus also influencing the selectivity in the methanol oxidation. In addition, adsorbed hydrogen on Pt(111) is shown to render the electro-oxidation of methanol less efficient. Graphical Abstract The difference between methanol oxidation in heterogeneous and electro-catalysis has been studied theoretically from first principles employing a grand-canonical approach.
      PubDate: 2017-03-27
      DOI: 10.1007/s12678-017-0370-1
       
  • A Carbon-Free Ag–Co 3 O 4 Composite as a Bifunctional Catalyst for
           Oxygen Reduction and Evolution: Spectroscopic, Microscopic and
           Electrochemical Characterization
    • Authors: Hatem M.A. Amin; Christoph J. Bondue; Santhana Eswara; Ute Kaiser; Helmut Baltruschat
      Abstract: Abstract A key challenge for rechargeable metal–air batteries is the development of a cost-effective bifunctional catalyst for both oxygen evolution (OER) and reduction (ORR) reactions. Here, we took the advantages of high OER activity of Co3O4 spinel and high ORR activity of Ag to develop a carbon-free oxygen electrode, e.g., for Li–air batteries. The optimized Ag + Co3O4 catalyst was further characterized and exhibited a good bifunctional activity in alkaline media. From rotating ring-disk electrode results, the mixed Ag + Co3O4 catalyst revealed significantly lower (∼320 mV) overpotential for ORR than single Co3O4, and a slightly lower overpotential than pure Ag. A four-electron pathway was also elucidated. The OER activity of the mixed catalyst is 1.5-fold compared to pure Co3O4, although the Co3O4 loading is only 10%, suggesting a large synergistic effect. The potential difference between OER and ORR (i.e., the sum of the overpotentials at 1 mA cm−2) is ca. 0.85 V, which is comparable to noble metal based catalysts. To better understand the origin of this synergism, an XPS analysis was performed, demonstrating that only after oxidation of the mixed catalyst, Co3O4 was reduced to Co(OH)2 at potentials of the ORR, probably due to the presence of Ag+. This redox switching, which was not observed for pure Co3O4, is a probable explanation for the increased catalytic activity. The morphology and the electrochemically active surface area of Ag on the surface were examined by electron microscopy and lead-underpotential deposition, respectively. These results also show that when 88% of the Ag surface is blocked by Co3O4 particles, the residual 12% free Ag sites altogether have a higher activity for ORR than the (100%) pure Ag surface, i.e., the activity per Ag site is increased by more than a factor of 10. The combination of low cost and high performance endows this catalyst as a promising candidate for energy devices, and the present synergistic effect opens a new track for high activity. Graphical Abstract ᅟ
      PubDate: 2017-03-24
      DOI: 10.1007/s12678-017-0364-z
       
  • Hydrogen Evolution Reaction on Nanostructures Electrodes—a Scenario
           on Stepped Silver Surfaces
    • Authors: M. F. Juárez; M. Ávila; A. Ruderman; E. Santos; E. P. M. Leiva; O. A. Oviedo
      Abstract: Abstract We have investigated the scenario for the hydrogen evolution reaction at stepped silver surfaces in acid solutions at high overpotentials using a simple kinetic model. Two independent types of sites, at the steps and at the terraces, were considered. The rate constants for the Volmer and Heyrovsky reactions were estimated. Both reactions occur with rate constant about two orders of magnitude larger at step sites than at terrace sites. Calculations of the activation energy for these reactions using our theory of electrocatalysis give similar results. Graphical Abstract Volmer reaction at terrace and step sites. Solvent interactions of the proton when approaches the surface
      PubDate: 2017-03-21
      DOI: 10.1007/s12678-017-0371-0
       
  • Direct Butane Utilization on Ni-(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 -(Ce 0.9 Gd
           
    • Authors: Hirofumi Sumi; Toshiaki Yamaguchi; Hiroyuki Shimada; Koichi Hamamoto; Toshio Suzuki; Scott A. Barnett
      Abstract: Abstract Nickel-yttria-stabilized zirconia-gadolinia-doped ceria (Ni-YSZGDC) composite anodes were investigated to use butane directly for microtubular solid oxide fuel cells (SOFCs). It was confirmed that mechanical mixing and sintering at 1400 °C for the YSZGDC composites resulted in the formation of a YSZ-GDC solid solution. The n-butane conversion for the cells with Ni-YSZGDC composite anodes was higher than that with Ni-YSZ anode. However, carbon deposition was observed on the Ni-YSZGDC composite anodes after durability test in n-butane. On the other hand, the performance was stable for the cell with the Ni-GDC anode in n-butane due to no carbon deposition. The Ni-GDC anode has a high electrochemical activity of carbon oxidation. Graphical Abstract ᅟ
      PubDate: 2017-03-15
      DOI: 10.1007/s12678-017-0369-7
       
  • An Artificial Photosynthesis System Based on Ti/TiO 2 Coated with Cu(II)
           Aspirinate Complex for CO 2 Reduction to Methanol
    • Authors: Simone Stülp; Juliano C. Cardoso; Juliana Ferreira de Brito; Jader Barbosa S. Flor; Regina Célia Galvão Frem; Fabiana Avoilo Sayão; Maria Valnice Boldrin Zanoni
      Abstract: Abstract A novel copper(II) aspirinate complex easily deposited onto nanotubes of Ti/TiO2 was successfully employed in the conversion of CO2 to methanol through the use of UV-Vis irradiation coupled to a bias potential of −0.35 V vs saturated calomel electrode. An average concentration of 0.8 mmol L−1 of methanol was obtained in 0.1 mol L−1 of sodium sulfate saturated with CO2 using a self-organized Ti/TiO2 nanotubular array electrode coated with a [Cu2(asp)4] complex. The influence exerted by CO2 and the complex over the behavior of photocurrent vs potential curves is discussed. Furthermore, a complete investigation of all parameters that tend to influence the global process of methanol production by the photoelectrocatalytic method such as applied potential, electrolyte, and time is also thoroughly presented. Graphical Abstract ᅟ
      PubDate: 2017-03-09
      DOI: 10.1007/s12678-017-0367-9
       
  • Electrochemical Reactions of Sodium 2-Ethylhexyl Sulfate Salt
    • Authors: Aleksandra Perek-Dlugosz; Adam Socha; Jacek Rynkowski
      Abstract: Abstract The electrochemical reactions of sodium 2-ethylhexyl sulfate (EHS) and its effect on the Zn2+ electroreduction have been investigated at a mercury electrode using cyclic voltammetry. It has been shown that the reduction takes place in two steps. The presence of EHS in the solution containing Zn2+ ions moves slightly the potential of zinc reduction towards more negative potentials and causes a slight increase in current density. The differential capacity-potential and differential capacity-time measurements indicate strong adsorption in a wide potential range on the electrode surface. In the potential range −0.46 to −0.86 V vs. saturated calomel electrode and at the concentration lower than the critical micelle concentration (CMC), adsorption for the longer time is hardly reversible. At the concentration higher than the CMC, the formation of hemispherical surface micelles is observed. The theoretical maximum degree of electrode coverage computed with the use of quantum-chemical calculations is equal to 3.53 × 1014 particles cm−2, and it is larger than the value determined experimentally from cyclic voltammograms. In the case of electrochemical reaction, at a current of 0.3 A, during 180 min, the obtained mineralization of EHS is only 3%. Graphical Abstract
      PubDate: 2017-03-01
      DOI: 10.1007/s12678-017-0356-z
       
  • The Promoting Role of Tungsten Oxides in the Anodic Oxidation of Methanol
           on Platinum-Based Catalysts
    • Authors: D. Cíntora-Juárez; A. L. Ocampo-Flores; L. C. Ordóñez; P. Roquero
      Abstract: Abstract Carbon-supported Pt-WO3 catalysts formulated with different proportions of platinum and tungsten were synthesized by thermal decomposition of metal carbonyl precursors. The activity of the PtWO3/C catalysts towards the methanol electrooxidation reaction (MOR) was evaluated in half-cell configuration and as anode catalyst in a direct methanol fuel cell device (DMFC) with a homemade membrane electrode assembly (MEA). The presence of WO3 increases significantly the catalyst activity, expressed by higher oxidation currents at lower potential values than those obtained with Pt/C. DMFC power output is comparable to that obtained by using a commercial MEA containing twice of the Pt loading at the anode. Electron microscopy and X-ray diffraction analysis (XRD) revealed that monoclinic WO2.92 and hexagonal WO3 phases coexist in the PtWO3/C catalysts. In samples with equal Pt loadings, the Pt particle size increases and its active area decreased as tungsten is added to the catalyst formulation. As the tungsten loading is increased and carbon content is diminished, hexagonal WO3 appears as the predominant crystalline phase. Graphical Abstract
      PubDate: 2017-03-01
      DOI: 10.1007/s12678-017-0361-2
       
 
 
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