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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)
  • Magnetically Induced Electrodeposition of Ni-Mo Alloy for Hydrogen
           Evolution Reaction
    • 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
  • 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
  • Synthesis and Oxygen Electrocatalysis of Iridium Oxide Nanosheets
    • Authors: Daisuke Takimoto; Katsutoshi Fukuda; Shu Miyasaka; Takanobu Ishida; Yusuke Ayato; Dai Mochizuki; Wataru Shimizu; Wataru Sugimoto
      Abstract: Rutile-type iridium dioxide (IrO2) is a well-known electrocatalyst, and its nanoparticle form has recently attracted attention as catalysts and co-catalysts in electrolyzers and fuel cells. In this study, we have successfully synthesized single crystalline iridium dioxide (IrO2) nanosheets with thickness of less than 0.7 nm via exfoliation of layered iridic acid H x Ir y O z ·nH2O, which was prepared via proton exchange of layered potassium iridate, K x Ir y O z ·nH2O. The electrochemically active surface area of the IrO2 nanosheet electrode was similar to or slightly lower than that of 3-nm IrO2 nanoparticles. Despite the lower active surface area, the mass activity for oxygen evolution reaction of IrO2 nanosheets was six times higher compared to that of IrO2 nanoparticles in 0.1 M HClO4 at 1.55 V vs. the reversible hydrogen electrode (17.4 vs. 2.9 A g−1). When IrO2 nanosheets were added to commercial Pt/C as a co-catalyst, increased stability against high potential cycling was obtained. After potential cycling between 1.0 and 1.5 V, the composite catalyst exhibited two times higher oxygen reduction activity compared to non-modified Pt/C. This durability enhancement is attributed to the suppression of the particle growth during the potential cycling test by the modification with IrO2 nanosheets. Graphical IrO2 nanosheets are highly active as electrocatalysts for O2 evolution and O2 reduction
      PubDate: 2016-12-28
      DOI: 10.1007/s12678-016-0348-4
  • High-Utilisation Nanoplatinum Catalyst (Pt@cPIM) Obtained via Vacuum
           Carbonisation in a Molecularly Rigid Polymer of Intrinsic Microporosity
    • Authors: Yuanyang Rong; Daping He; Richard Malpass-Evans; Mariolino Carta; Neil B. McKeown; Murilo F. Gromboni; Lucia H. Mascaro; Geoffrey W. Nelson; John S. Foord; Philip Holdway; Sara E. C. Dale; Simon Bending; Frank Marken
      Abstract: Polymers of intrinsic microporosity (PIM or here PIM-EA-TB) offer a highly rigid host environment into which hexachloroplatinate(IV) anions are readily adsorbed and vacuum carbonised (at 500 °C) to form active embedded platinum nanoparticles. This process is characterised by electron and optical microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods, which reveal that the PIM microporosity facilitates the assembly of nanoparticles of typically 1.0 to 2.5-nm diameter. It is demonstrated that the resulting carbonised “Pt@cPIM” from drop-cast films of ca. 550-nm average thickness, when prepared on tin-doped indium oxide (ITO), contain not only fully encapsulated but also fully active platinum nanoparticles in an electrically conducting hetero-carbon host. Alternatively, for thinner films (50–250 nm) prepared by spin coating, the particles become more exposed due to additional loss of the carbon host. In contrast to catalyst materials prepared by vacuum-thermolysed hexachloroplatinate(IV) precursor, the platinum nanoparticles within Pt@cPIM retain high surface area, electrochemical activity and high catalyst efficiency due to the molecular rigidity of the host. Data are presented for oxygen reduction, methanol oxidation and glucose oxidation, and in all cases, the high catalyst surface area is linked to excellent catalyst utilisation. Robust transparent platinum-coated electrodes are obtained with reactivity equivalent to bare platinum but with only 1 μg Pt cm−2 (i.e. ~100% active Pt nanoparticle surface is maintained in the carbonised microporous host). Graphical ᅟ
      PubDate: 2016-12-12
      DOI: 10.1007/s12678-016-0347-5
  • Facile Synthesis of Cobalt Oxide Nanoparticles by Thermal Decomposition of
           Cobalt(II) Carboxamide Complexes: Application as Oxygen Evolution Reaction
           Electrocatalyst in Alkaline Water Electrolysis
    • Authors: Soraia Meghdadi; Mehdi Amirnasr; Mohammad Zhiani; Fariba Jallili; Meysam Jari; Mahsa Kiani
      Abstract: Cobalt oxide nanoparticles, Co3O4 (1) and Co3O4 (2), have been synthesized by thermal decomposition of [CoII(bqbenzo)] and [CoII(bqb)], respectively. The morphology of these oxides is influenced by the difference in the structure of bqbenzo2− {3,4-bis(2-quinolinecarboxamido) benzophenone and, bqb2− {bis(2-quinolinecarboxamido)-1,2-benzen}, only differing in a benzoyl substituent. The products were characterized by XRD, FE-SEM, and FT-IR spectroscopy. The catalytic activity of the oxides was examined in oxygen evolution reaction (OER) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The Co3O4 oxides (1 and 2) exhibited higher catalytic activity compared to 10 wt% Pt/C in terms of obtained current density at 0.8 V; ∼23.3 versus 6.1 mA cm−2, respectively. However, the aging tests of the two oxides in OER revealed that Co3O4 (1) is more stable than Co3O4 (2). These results demonstrated that the Co3O4 (1) has a superior performance which can be employed in the alkaline water electrolyzer anode. Graphical Co3O4 nanoparticles are synthesized via calcination of [Co(bqbenzo)] and [Co(bqb)] giving Co3O4 (1) and Co3O4 (2), respectively. Both oxides exhibit pronounced oxygen evolution activity compared to 10 wt% Pt/C and Co3O4 (1), with more robust polymorphic structure, exhibits remarkable stability during OER cycling.
      PubDate: 2016-12-10
      DOI: 10.1007/s12678-016-0345-7
  • A Simple Method for the Electrodeposition of WO 3 in TiO 2 Nanotubes:
           Influence of the Amount of Tungsten on Photoelectrocatalytic Activity
    • Authors: Alysson Stefan Martins; Paulo Jorge Marques Cordeiro-Junior; Luciana Nuñez; Marcos Roberto de Vasconcelos Lanza
      Abstract: Although TiO2 is used in a wide range of photocatalytic applications, its activity can be improved considerably by coupling with a metal oxide, such as WO3, in a bicomponent systems. However, the amount of WO3 deposited onto TiO2 is of crucial importance because it may influence the optical and electrochemical properties and, consequently, the photocatalytic activity. In the present study, a series of modified electrodes were prepared by electrochemical deposition of different amounts of WO3 onto TiO2 nanotubes (TiO2-NTs). Energy dispersive X-ray analysis revealed that increasing amounts of W were deposited with increased deposition times between 5 and 60 min, and that electrodes EW5, EW10, EW15, EW30, EW45, and EW60 contained 0.74, 1.27, 1.60, 4.85, 10.10, and 13.30 at.% W, respectively. X-ray diffraction patterns confirmed the presence of the WO3 crystalline phase and the TiO2 anatase. Diffuse reflectance spectra of electrodes EW5, EW10, and EW15 exhibited the most intense absorbances, and their energy band-gap values were in the region of 2.90 eV, which is comparable with the value for TiO2-WO3 bicomponent. The photoactivities of electrodes EW5 and EW10 containing low amounts of W (~1 %) exhibited photocurrents that were, respectively, 13 and 25 % higher than that of the unmodified TiO2-NTs electrode. Electrodes containing larger amounts of W showed correspondingly reduced photocurrents. The application of electrodes E0 and EW10 on the photoelectrocatalytic oxidation of Bisphenol-A (BPA) revealed excellent removal rate which BPA was not detected after 30 min of reaction. The electrode EW10 achieved ~64 % of total organic carbon (TOC) in the end of degradation, more effective compared to the electrode E0 (58 %). These findings demonstrate that photoelectrocatalytic efficiency is strictly dependent on morphology and amount of WO3. Optimal deposition of WO3 favors the formation of WO3-TiO2 heterojunctions, thereby improving the performance of the semiconductor. Graphical abstract ᅟ
      PubDate: 2016-11-30
      DOI: 10.1007/s12678-016-0335-9
  • Performance and Mechanism of In Situ Electro-Catalytic Flue Gas
           Desulfurization via Carbon Black-Based Gas Diffusion Electrodes Doped with
    • Authors: Ze Chen; Heng Dong; Hongbing Yu; Han Yu; Min Zhao; Xi Zhang
      Abstract: Flue gas desulfurization (FGD) based on electro-chemical technologies is efficient and environment-friendly. However, the low dissolved oxygen concentration, insufficient active sites, and high cost of electrode materials are still three bottlenecks needed to be solved. In this work, a series of novel carbon black-based gas diffusion electrodes (GDEs) doped with different multi-walled carbon nanotube (MWCNT) amounts were developed to generate H2O2 via oxygen reduction reaction (ORR) for in situ FGD. The influence of current density and electrolyte concentration for desulfurization performance was investigated. As a result, the GDEs doped with 100 mg MWCNTs gave the highest desulfurization efficiency (98.0%) and the lowest energy consumption (1.7 kW h kg−1) owing to its good balance on the porous structure, conductivity, and ORR activity. An appropriate current density (3.54 mA cm−2) and electrolyte concentration (50 mM) are conducive to the two-electron ORR and desulfurization. While the excessive values would cause some side reactions and the occupations of active sites by the SO4 2−. This compact system exhibits advantages of high desulfurization efficiency and low-energy consumption with no secondary pollution, providing an alternative way for in situ FGD in industrial application. Graphical In situ electro-chemical flue gas desulfurization by H2O2 generated on novel carbon black-based gas diffusion electrodes doped with different multi-walled carbon nanotube amounts.
      PubDate: 2016-11-29
      DOI: 10.1007/s12678-016-0346-6
  • Methanol and Ethanol Electrooxidation on PtRu and PtNiCu as Studied by
           High-Resolution In Situ Electrochemical NMR Spectroscopy with
           Interdigitated Electrodes
    • Authors: Eric G. Sorte; Safia Jilani; YuYe J. Tong
      Abstract: Following a recent short communication (J. Electroanal. Chem. 769 (2016) 1–4) in which we demonstrated the feasibility and proof-of-concept results of using interdigitated metal electrodes to achieve high-resolution in situ electrochemical solution NMR for studying electrochemically driven reactions such as those involved in electrolysis and electrocatalysis, we report herein a more detailed technical description of the technique and its application to studying methanol and ethanol electrooxidation on PtRu and PtNiCu electrocatalysts. Graphical 13C NMR data from ethanol oxidation with a PtNiCu catalyst. (a) C NMR resonances as a function of time, showing the growth of all product peaks. (b) Comparison of the final spectra of ethanol oxidation reactions performed with PtNiCu (black, upper) and PtRu (blue, lower) catalysts. Differences in the relative intensities of the product peaks can be identified.
      PubDate: 2016-11-24
      DOI: 10.1007/s12678-016-0344-8
  • Rotating Disk Slurry Au Electrodeposition at Unsupported Carbon Vulcan
           XC-72 and Ce 3+ Impregnation for Ethanol Oxidation in Alkaline Media
    • Authors: Luis E. Betancourt; Rolando Guzmán-Blas; Si Luo; Dario J. Stacchiola; Sanjaya D. Senanayake; Maxime Guinel; Carlos R. Cabrera
      Abstract: A robust electrodeposition method consisting of the rotating disk slurry electrode (RoDSE) technique to obtain Au nanoparticles highly dispersed on a conductive carbonaceous support, i.e., Vulcan XC-72R, for ethanol electrooxidation reaction in alkaline media was developed. Ceria was used as a cocatalyst using a Ce(III)-EDTA impregnation method in order to enhance the catalytic activity and improve the catalyst’s overall stability. The RoDSE method used to obtain highly dispersed Au nanoparticles does not require the use of a reducing agent or stabilizing agent, and the noble-metal loading was controlled by the addition and tuning of the metal precursor concentration. Inductively coupled plasma and thermogravimetric analysis indicated that the Au loading in the catalyst was 9 %. Particle size and characteristic Au fcc crystal facets were determined by X-ray diffraction. The morphology of the catalyst was also investigated using electron microscopy techniques. In addition, X-ray absorption spectroscopy was used to corroborate the presence and identify the oxidation state of Ce in the system and to observe if there are any electronic interactions within the 8 % Au/CeOx/C system. Cyclic voltammetry of electrodeposited 9 % Au/C and Ce-promoted 8 % Au/C showed a higher catalytic current density for ethanol oxidation when compared with commercially available catalysts (20 % Au/C) of a higher precious metal loading. In addition, we report a higher stability toward the ethanol electrooxidation process, which was corroborated by 1 mV/s linear sweep voltammetry and chronoamperometric studies. Graphical ᅟ
      PubDate: 2016-11-19
      DOI: 10.1007/s12678-016-0342-x
  • 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
  • OER Activity of Ir-Ta-Zr Composite Anode as a Counter Electrode for
           Electrohydrogenation of Toluene
    • Authors: Kohei Nagai; Kensaku Nagasawa; Shigenori Mitsushima
      Abstract: The organic chemical hydride method using the toluene (TL)/methylcyclohexane (MCH) system is one of the prospective energy carrier technologies for hydrogen storage and transportation. The direct electrohydrogenation of toluene with water decomposition using electric power is a highly efficient energy conversion process for the MCH synthesis. In this process, an IrO2-based directionally stable electrode® (DSE®) for the oxygen evolution reaction (OER) is used as the anode because of its good electrocatalytic activity and durability. However, further improvement in the activity is needed for practical applications. In this study, the effect of Zr addition substituted for Ta in IrO2-Ta2O5/Ti, which is a typical OER anode, on the electrocatalytic activity has been investigated in sulfuric acid with TL contamination. The activity of both the IrO2-Ta2O5/Ti and the IrO2-Ta2O5-ZrO2/Ti was higher and less affected by TL contamination than the IrO2/Ti. The activity of the IrO2-Ta2O5-ZrO2/Ti increased with the Zr content. The Zr addition increased the real surface area along with the increase in the double layer capacitance; on the other hand, the increase in activity was more than that of the surface area. Therefore, the Zr additive would affect not only the real surface area increase, but also the electrocatalytic activity. Graphical Schematic drawing of electrolyzer for direct electrohydrogenation of toluene with water decomposition (left). Oxygen evolution reaction current on Ir50Ta20Zr30-oxide/Ti, Ir50Ta50-oxide/Ti, and IrO2/Ti with (dash) and without (solid) toluene contamination as a function of the potential in 1 M H2SO4 at 60 oC (right).
      PubDate: 2016-08-11
      DOI: 10.1007/s12678-016-0325-y
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