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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]
  • 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
      Pages: 87 - 94
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0342-x
      Issue No: Vol. 8, No. 2 (2017)
       
  • 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
      Pages: 95 - 102
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0344-8
      Issue No: Vol. 8, No. 2 (2017)
       
  • Performance and Mechanism of In Situ Electro-Catalytic Flue Gas
           Desulfurization via Carbon Black-Based Gas Diffusion Electrodes Doped with
           MWCNTs
    • Authors: Ze Chen; Heng Dong; Hongbing Yu; Han Yu; Min Zhao; Xi Zhang
      Pages: 103 - 114
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0346-6
      Issue No: Vol. 8, No. 2 (2017)
       
  • 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
      Pages: 115 - 121
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0335-9
      Issue No: Vol. 8, No. 2 (2017)
       
  • 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
      Pages: 122 - 131
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0345-7
      Issue No: Vol. 8, No. 2 (2017)
       
  • 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
      Pages: 132 - 143
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0347-5
      Issue No: Vol. 8, No. 2 (2017)
       
  • 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
      Pages: 144 - 150
      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: 2017-03-01
      DOI: 10.1007/s12678-016-0348-4
      Issue No: Vol. 8, No. 2 (2017)
       
  • 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: 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 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
       
  • Fates of Hydrogen During Alumina Growth Below Yttria Nodules in FeCrAl(RE)
           at Low Partial Pressures of Water
    • Authors: Vedad Babic; Christine Geers; Bo Jönsson; Itai Panas
      Abstract: Oxidation of FeCrAl(Re), when exposed to ∼35 ppm of water as sole supply of oxygen in predominantly nitrogen atmosphere, has two characteristic signatures. One is the internal nitridation owing to chromia nodules acting windows toward nitrogen permeation locally short-circuiting the protective α-Al2O3 scale. The second remarkable feature is the growth of thick, apparently defect-rich alumina scale under yttria-rich nodules. Hence, one part of the present study comprises exploratory DFT calculations to discriminate between the impacts of chromia and yttria viz. nitrogen permeation. The second part concerns boundary conditions for apparent rapid growth of alumina under yttria nodules. Yttria-associated surface energy stabilization of defect-rich alumina in presence of water was argued to involve hydrolysis-driven hydroxylation of said interface. Subsequent inward growth of the alumina scale was associated with outward diffusion of oxygen vacancies to be accommodated by the remaining proton producing a hydride ion upon surfacing at yttria-decorated alumina interfaces. The latter comprises the cathode process in a quasi-Wagnerian context. Two fates were discussed for this surface ion. One has H−–H+ recombination to form H2 at the interface in conjunction with OH– accommodation upon hydration, while the second allows hydrogen to be incorporated at VO sites in hydroxylated grain boundaries of the growing alumina scale. The latter was taken to explain the experimentally observed rapid oxide growth under yttria-rich nodules. Space charge due to proton reduction was proposed to cause transient inward cationic drag. Graphical Impacts of chromia and yttria nodules, coexisting in an alumina barrier oxide, viz. nitrogen permeation at low partial pressures of water was addressed. Furthermore, yttria-associated surface energy stabilization of defect-rich alumina in presence of water was argued to involve hydrolysis-driven hydroxylation of the interfaces. Inwards oxide growth is conditioned by dis posal of hydrogen. Two fates were discussed. One has H−–H+ recombination to form H2 at the interfaces, while the second would allow hydrogen to be incorporated in oxygen vacancies in the hydroxylated grain boundaries of the growing alumina scale.
      PubDate: 2017-03-16
      DOI: 10.1007/s12678-017-0368-8
       
  • 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: 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 ᅟ
      PubDate: 2017-03-15
      DOI: 10.1007/s12678-017-0369-7
       
  • Oxygen Reduction in Alkaline Media—a Discussion
    • Authors: Anna Ignaczak; Renat Nazmutdinov; Aleksej Goduljan; Leandro Moreira de Campos Pinto; Fernanda Juarez; Paola Quaino; Gustavo Belletti; Elizabeth Santos; Wolfgang Schmickler
      Abstract: We propose a complete reaction sequence for oxygen reduction in alkaline solutions, in which the first two steps occur in the outer sphere mode. The oxygen-oxygen bond is broken in the third step, which involves adsorption of OH, which is desorbed in the last step. We have investigated the sequence by quantum-chemical methods and determined the energies of activation. Whether the reaction follows a four- or a two-electron mechanism, depends critically on the energy of adsorption of OH. We surmise that our mechanism holds on all electrodes which interact weakly with oxygen, in particular on gold, silver, and graphite. We explain, why Au(100) is a better catalyst than Au(111), why at high overpotentials the reaction on Au(100) reverts to a two-electron mechanism, and why this does not happen on silver. Graphical We propose a mechanism for oxygen reduction in alkaline solution and support each step by theoretical calculations based on DFT and on our own theory. In particular we explain the central role of OH adsorption in the breaking of the oxygen-oxygen bond
      PubDate: 2017-03-10
      DOI: 10.1007/s12678-017-0365-y
       
  • 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: 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 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: 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
      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: 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
      PubDate: 2017-03-01
      DOI: 10.1007/s12678-017-0361-2
       
  • 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
      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 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: 2017-02-27
      DOI: 10.1007/s12678-017-0362-1
       
  • 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
      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
      PubDate: 2017-02-24
      DOI: 10.1007/s12678-017-0360-3
       
  • Impedance Measurement and Selection of Electrochemical Equivalent Circuit
           of a Working PEM Fuel Cell Cathode
    • Authors: Kazimierz Darowicki; Lukasz Gawel
      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 The equivalent electrical circuit of an operating fuel cell cathode
      PubDate: 2017-02-23
      DOI: 10.1007/s12678-017-0363-0
       
  • Synergistic Ion Intercalations for High-Yield Synthesis of Li-Doped
           Graphene Nanosheets as an Efficient Electrocatalyst for Oxygen Reduction
           Reaction
    • 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
       
  • 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
       
  • Understanding the Influence of the Biomass-Derived Alcohols on the
           Activity and Stability of Pt Nanoparticles Supported on Graphene
           Nanoribbons
    • 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
       
 
 
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