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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  [2336 journals]
  • CO-Terminated Platinum Electrodeposition on Nb-Doped Bulk Rutile TiO 2
    • Authors: Sebastian Proch; Kensaku Kodama; Shuhei Yoshino; Naoko Takahashi; Naohiko Kato; Yu Morimoto
      Pages: 362 - 375
      Abstract: Abstract Nanoparticulate platinum on carbon as oxygen reduction electrocatalyst suffers from two major drawbacks, namely, low specific activity of the Pt particles and corrosion instability of the carbon support under hydrogen starvation conditions (reverse current degradation). Both issues can be tackled by Pt thin films on TiO2 support. Platinum films were synthesized on commercially available Nb-doped bulk TiO2 electrodes via electrodeposition from Ar- (bulk amounts) and CO-saturated solutions (monolayer amounts). The platinized electrodes were tested for ORR activity in a voltammetric fashion, and the field-free semiconductor properties were evaluated by a combination of X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), photoelectron yield spectroscopy (PYS), electrochemical impedance spectroscopy (EIS), and bulk conductivity measurements. The deposition of bulk amounts of Pt leads to a situation where the catalytic activity is directly correlated to the conductivity of the electrode. Raising the majority carrier density in the Nb-doped TiO2, via proton intercalation in aqueous HClO4 or glycol, drastically increased the activity. In case of monolayer deposits (CO-terminated deposition), intercalation has practically no effect on activity. Thus, the hypothesis is formed that unfavorable electronic interaction of the TiO2 support with small amounts of platinum drastically reduces ORR activity, an effect which is not observed for monolayer amounts of Pt deposited on gold. Graphical Abstract Too Much Interaction: The oxygen reduction activity of bulk amounts of Pt, deposited on Nb-doped TiO2, can be significantly improved by raising the carrier density (via proton intercalation). Such treatment has no effect if monolayer amounts are deposited. This observation is attributed to unfavorable Pt/TiO2 interactions for minute amounts of Pt.
      PubDate: 2016-09-01
      DOI: 10.1007/s12678-016-0316-z
      Issue No: Vol. 7, No. 5 (2016)
  • Co-sputtered Pt x Pd y Al z thin film electrocatalysts for the production
           of hydrogen via SO 2 (aq) electro-oxidation
    • Authors: A. Falch; V. A. Badets; C. Labrugère; R. J. Kriek
      Pages: 376 - 390
      Abstract: Abstract A co-sputtered PtxPdyAlz ternary system was investigated for potential use as anode catalyst for the electro-oxidation of aqueous sulphur dioxide (SO2), a key reaction in the hybrid sulphur (HyS) process for splitting water into hydrogen and oxygen. Combining the noble metals Pt and Pd with Al resulted in no significant improvement in onset potential; however, current output was improved for the majority of the electrocatalysts evaluated. Of these electrocatalysts, only a single ternary composition exhibited improved stability when compared to pure Pt. It was found that a combination of Pt40Pd57Al3 (annealed at 900 °C) exhibited superior performance when compared to pure Pt and the previously determined best binary electrocatalyst, i.e. Pt3Pd2. Current density ( Pt−1) increased from 108.11 to 181.21 and finally to 396.73 for Pt, Pt3Pd2 and Pt40Pd57Al3, respectively, indicating an increase in activity that correlates with a decrease in Pt content. Atomic force microscopy (AFM) revealed an increase in surface roughness for Pt, Pt3Pd2 and Pt40Pd57Al3, while the occurrence of metal interaction and certain degrees of Al migration (a result of annealing) was confirmed for Pt40Pd57Al3 by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD). Graphical Abstract The electro-oxidation of aqueous SO2 is a key reaction in the hybrid sulphur (HyS) process for water-splitting. A sputtered PtxPdyAlz ternary system was investigated for potential use as anode catalyst. It was found that a combination of Pt40Pd57Al3 annealed at 900 °C, exhibited noteworthy performance when compared to pure Pt and the previously determined best binary electrocatalyst, i.e. Pt3Pd2. Current density ( Pt−1) increased from 108.11 to 181.21 and finally to 396.73 for Pt, Pt3Pd2, and Pt40Pd57Al3, respectively, indicating an increase in activity that correlates with a decrease in Pt content.
      PubDate: 2016-09-01
      DOI: 10.1007/s12678-016-0319-9
      Issue No: Vol. 7, No. 5 (2016)
  • Investigation of Electrochemical Properties of Model Lanthanum Strontium
           Cobalt Ferrite-Based Cathodes for Proton Ceramic Fuel Cells
    • Authors: Chung-Yul Yoo; Dae Sik Yun; Sun-Young Park; Jaeku Park; Jong Hoon Joo; Haein Park; Minseok Kwak; Ji Haeng Yu
      Pages: 280 - 286
      Abstract: The electrochemical properties of La0.6Sr0.4Co0.2Fe0.8O3-δ-based cathodes are studied as model electrodes for proton ceramic fuel cells. The electrochemical performance of symmetric cells with porous cathodes (La0.6Sr0.4Co0.2Fe0.8O3-δ, La0.6Sr0.4Co0.2Fe0.8O3-δ–BaCe0.9Y0.1O3-δ, and La0.6Sr0.4Co0.2Fe0.8O3-δ–BaZr0.8Y0.2O3-δ), investigated as a function of oxygen and water partial pressures, follows the order La0.6Sr0.4Co0.2Fe0.8O3-δ–BaCe0.9Y0.1O3-δ ≥ La0.6Sr0.4Co0.2Fe0.8O3-δ >> La0.6Sr0.4Co0.2Fe0.8O3-δ–BaZr0.8Y0.2O3-δ. The results indicate that the cathode performance of La0.6Sr0.4Co0.2Fe0.8O3-δ–BaCe0.9Y0.1O3-δ is enhanced mainly due to the extension of the effective triple phase boundary, whereas that of La0.6Sr0.4Co0.2Fe0.8O3-δ–BaZr0.8Y0.2O3-δ is lowered due to the poor proton conductivity along the percolated BaZr0.8Y0.2O3-δ particles. From the observed oxygen partial pressure dependence, the rate-determining step of the above cathode polarization reaction is principally ascribed to the oxygen reduction reaction. Graphical abstract Schematics of the cathode reaction mechanism at the surface of the LSCF, LSCF-BCY, and LSCFBZY cathodes
      PubDate: 2016-07-01
      DOI: 10.1007/s12678-016-0306-1
      Issue No: Vol. 7, No. 4 (2016)
  • Erratum to: 3D π-Conjugated Poly(amic) Acid Polymer as Support Matrices
           for Ethanol Electro-Oxidation on Palladium and Platinum Catalysts
    • Authors: Victor M. Kariuki; Jing Zhang; Magdalena Parlinska-Wojtan; Omowunmi A. Sadik
      Pages: 355 - 355
      PubDate: 2016-05-17
      DOI: 10.1007/s12678-016-0315-0
      Issue No: Vol. 7, No. 4 (2016)
  • 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
      Abstract: 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 Abstract ᅟ
      PubDate: 2016-10-15
      DOI: 10.1007/s12678-016-0333-y
  • 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
      Abstract: 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 Abstract ᅟ
      PubDate: 2016-10-14
      DOI: 10.1007/s12678-016-0332-z
  • Design and Development of Instrumentations for the Preparation of Platinum
           Single Crystals for Electrochemistry and Electrocatalysis Research. Part
           1: Semi-Automated Crystal Growth
    • Abstract: Abstract In this contribution, we report on a novel design of semi-automated system for the growth of spherical platinum (Pt) single crystals. The system is based on the flame fusion methodology, where the crystal melting/solidification process is controlled by the vertical movement of a hydrogen–oxygen flame by using an actuator. The paper systematically examines the impact of several process variables on the crystal growth. First, the hydrogen–oxygen flame is optimized through control of the gas flow rate and the mixing ratio to ensure the formation of high-quality platinum single crystals. The procedure of crystal growth is documented in a step-by-step manner, starting with cleaning of the Pt wire, followed by the initial formation of metallic sphere, and ending with repetitive zone refining combined with chemical etching. The equilibrium shape of the platinum single crystals is discussed, and the individual low and high Miller index facets identified and visualized. The critical step in the single-crystal growth, the repetitive zone refining, is semi-automated in order to ensure the highest quality crystals and reproducibility, and to minimize any human error. Graphical Abstract ᅟ
      PubDate: 2016-10-05
      DOI: 10.1007/s12678-016-0331-0
  • Rutile TiO 2 Supported Pt as Stable Electrocatalyst for Improved Oxygen
           Reduction Reaction and Durability in Polymer Electrolyte Fuel Cells
    • Authors: P. Dhanasekaran; S. Vinod Selvaganesh; L. Sarathi; Santoshkumar D. Bhat
      Abstract: Abstract In the present study, electrochemically stable titanium dioxide with tunable phase composition as catalyst support for polymer electrolyte fuel cells (PEFCs) is described. The different TiO2 phases are prepared by heat treatment at different temperatures, followed by deposition of platinum metal nanoparticles through a colloidal method. The platinum nanoparticles deposited on rutile TiO2-800 exhibit higher oxygen reduction reaction (ORR) activity and better fuel cell performance compared to Pt supported on anatase TiO2. The structural effect, dispersion of platinum nanoparticles, and oxidation states are studied by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The accelerated durability test shows that platinum deposited on TiO2-800 exhibits significant enhancement in the stability and corrosion resistance. Although the initial activity of Pt deposited on TiO2-800 is lower than for Pt deposited on carbon, during accelerated durability test (ADT) it retains more than 60 % of the initial electrochemical active surface area (ECSA) even after 20,000 potential cycles. In comparison, only 10 % are left for Pt supported on carbon after 10,000 cycles. Graphical Abstract Proposed schematic of Pt deposited on rutile TiO2 towards oxygen reduction reaction in polymer electrolyte membrane fuel cells.
      PubDate: 2016-09-14
      DOI: 10.1007/s12678-016-0329-7
  • Formic Acid Oxidation at Ru@Pt Core-Shell Nanoparticles
    • Authors: Ehab N. El Sawy; Peter G. Pickup
      Abstract: Abstract Formic acid oxidation has been investigated at Ru@Pt core-shell nanoparticles for Pt coverages ranging from 0.4 to 1.9 monolayers (ML), in order to determine how the bi-functional and electronic effect of the Ru core and compression of the Pt lattice influence activity. By comparing voltammetric results with those for CO stripping and bulk oxidation, it has been shown that the electronic effect of the Ru core on CO oxidation is the dominant factor influencing formic acid oxidation. Thus, the indirect pathway through adsorbed CO begins at the lowest potential for sub-monolayer Pt coverages, and the formic acid oxidation rate increases as the Pt coverage is increased towards one monolayer. However, the electronic effect of the Ru becomes muted as a second Pt layer is added, CO oxidation is shifted to higher potentials and formic acid oxidation activity drops. The optimum coverage of Pt depends on a balance between the electronic effects of the Ru core on the promotion of CO oxidation and inhibition of formic acid oxidation through the direct pathway that does not produce adsorbed CO. Thus, a coverage of 0.85 ML Pt provided the best activity for 0.5 M formic acid, while 1.3 ML gave a particularly high activity for 2 M formic acid at low potentials. Graphical Abstract One monolayer of Pt on a Ru core provides high activity for formic acid oxidation due to a strong electronic effect, while this becomes muted when a second layer of Pt is added
      PubDate: 2016-09-10
      DOI: 10.1007/s12678-016-0328-8
  • Nitrite Reduction Enhancement on Semiconducting Electrode Decorated with
           Copper(II) Aspirinate Complex
    • Authors: Fabiana A. Sayão; Jader Barbosa da Silva Flor; Regina Célia Galvão Frem; Simone Stulp; Juliano C. Cardoso; Maria V. B. Zanoni
      Abstract: Abstract The present work seeks to describe a new approach characterized by copper(II) aspirinate complex deposited onto nanotube TiO2 electrodes as mediator of electron transfer during nitrite reduction, aiming at achieving a faster removal of nitrite to nitrogen species oxides. Thin films of copper aspirinate ([Cu2(asp)4]) on the Ti/TiO2 nanotube surface are easily obtained following multi-scans (100 cycles) recorded for the Ti/TiO2 electrode in 0.1 mol L−1 NaCl, pH 4, containing 5.0 × 10−4 mol L−1 of the copper coordination compound. The complex showed high adherence while the cyclic voltammograms presented redox peaks at −0.15/+0.15 V, which was attributed to the reduction of Cu(II) to Cu(I). Following 5 min of treatment using photoelectrocatalysis on Ti/TiO2-[(Cu)2Asp4] electrode, a total removal of nitrite was observed, which was found to be at least four times faster compared to Ti/TiO2 electrode. Concomitantly, we also observed a relatively good conversion to nitrogen-containing gaseous species (56 %) besides the formation of 42 % of ammonia. The results, in effect, also indicate that nitrate and nitrite are not detectable in the treated solution up to levels of 0.5 mg L−1. The method under consideration has successfully accounted for the maximum limit of nitrite recommended in drinking water which has been set to 1 mg L−1. Graphical Abstract Nitrite reduction by Ti/TiO2 NTs with Cu(II) aspirinate complex.
      PubDate: 2016-09-10
      DOI: 10.1007/s12678-016-0327-9
  • Preparation and Evaluation of Nickel Nanoparticles Supported on the
           Polyvinylpyrrolidone-Graphene Composite as a Durable Electrocatalyst for
           HER in Alkaline Media
    • Authors: Mohammad Zhiani; Saeedeh Kamali
      Abstract: Abstract Low-cast non-noble-based catalysts with high activity and durability are the choices to replace expensive Pt-based catalysts for hydrogen evolution reaction (HER). In this work, polyvinylpyrrolidone (PVP)-modified graphene (PVP-rGO) was synthesized as a composite with a high surface area and additional functional groups for Ni nanoparticle support. Loading of nickel nanoparticles on the PVP-rGO was optimized to obtain an effective non-noble catalyst (Ni/PVP-rGO) for HER in alkaline media. Inductively coupled plasma optical emission spectrometry (ICP-OES) results demonstrated a relatively good accordance between theoretical and experimental metal loading by this facile synthesis procedure. The structure and morphology of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR) techniques. The activity and stability of the prepared catalysts (with and without PVP) were investigated at HER in alkaline media by different electrochemical techniques. A Tafel slope of 119 mV dec−1 was obtained for Ni/PVP-rGO, which was consistent with the Volmer reaction as the rate determining step (RDS) of HER mechanism. Also, an acceptable durability in HER performance was obtained by Ni/PVP-rGO (working over 62.5 h and 5000 cycles without a notable lost). These results make it as a promising catalyst which could be employed in the cathode side of water electrolyzer in alkaline media. Graphical Abstract Durability enhancement by incorporation of PVP in the composite support of Ni nano-particles for HER in alkaline media
      PubDate: 2016-09-08
      DOI: 10.1007/s12678-016-0330-1
  • Titania Nanotube Arrays (TNAs) as Support for Oxygen Reduction Reaction
           (ORR) Platinum Thin Film Catalysts
    • Authors: Sebastian Proch; Shuhei Yoshino; Naohiko Kato; Naoko Takahashi; Yu Morimoto
      Abstract: Abstract Recently, we showed that Nb-doped bulk TiO2 electrodes can be functionalized with minute amounts of Pt via CO-terminated Pt deposition but optimization of the conductivity of these electrodes via proton intercalation did not change the catalytic activity of the Pt deposits. Here, it is shown that intercalation of H species in 0.27 wt% NH4F in glycol raises the catalytic activity of Pt deposited in a CO-terminated fashion if it is used on nanostructured (titania nanotube arrays) rather than titania bulk electrodes. Catalyst support tuning becomes feasible for nanostructures but effects of the intercalation treatment fade away within days. Moreover, catalytic activities of ultra-low Pt amounts, as determined by ICP-MS, on TNAs are very low compared to deposition on gold. This effect is attributed to high strain exerted on the Pt thin layers by the oxide support. Graphical Abstract Size Does Matter: Unlike bulk TiO2 electrodes, titania nanotube arrays (TNAs) are catalyst supports that facilitate tuning of the oxygen reduction response of sub- and monolayer amounts of Pt (from CO-terminated electrodeposition) via proton intercalation.
      PubDate: 2016-08-26
      DOI: 10.1007/s12678-016-0326-x
  • Methanol Oxidation in Alkaline Medium Using PtIn/C Electrocatalysts
    • Authors: M. C. L. Santos; C. A. Ottoni; R. F. B. de Souza; S. G. da Silva; M. H. M. T. Assumpção; E. V. Spinacé; A. O. Neto
      Abstract: Abstract Pt/C and PtIn/C with atomic ratios of 90:10, 70:30, and 50:50 were investigated for methanol electro-oxidation in alkaline media by using cyclic voltammetry (CV), chronoamperometry (CA), and direct methanol alkaline fuel cell (DMAFC). All electrocatalysts were synthesized using sodium borohydride method with 20 wt% of metals loading on carbon. X-ray diffraction (XRD) analysis revealed that bimetallic PtIn had faced centered cubic structure and, also, confirmed alloy formation for PtIn/C nanoparticles. Transmission electron micrographs showed metal nanoparticles with average particle size between 3.0 and 5.0 nm; however, the particle size increases when the In content was increased in PtIn/C. In the CV experiments, the onset potential of methanol electro-oxidation shifted to lower values as the indium content increased. Chronoamperometry experiments and direct methanol alkaline fuel cell suggested PtIn/C (70:30) as the most promising material for methanol electro-oxidation: this result could be explained by the presence of Pt and In in close contact (electronic effect) as the occurrence of oxy-hydroxy interactions. Graphical Abstract Chronoamperometry curves for PtIn/C electrocatalysts at 25 °C.
      PubDate: 2016-08-17
      DOI: 10.1007/s12678-016-0324-z
  • Electrocatalysis of NADH on 3,5-Dinitrobenzoic Acid Encapsulated on
           Multiwalled Carbon Nanotube-Modified Electrode
    • Authors: R. Moscoso; E. Inostroza; S. Bollo; J. A. Squella
      Abstract: We report that glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNTs) can encapsulate or entrap 3,5-dinitrobenzoic acid (35DNB) generating a 35DNB-MWCNTGC electrode. After electrochemical reduction in situ of only one nitro group of 35DNB, it turns into the hydroxylamine derivative (R-NHOH), which can be further oxidized to the nitroso derivative (R-NO). Then, R-NO/R-NHOH redox couple was electrogenerated in situ by cycling the potential between 0.20 and −0.20 V vs Ag/AgCl. The very well-defined and persistent redox couple was characterized with a formal potential, E o ’ = −28 mV vs Ag/AgCl at a scan rate of 20 mV s−1. Using the Laviron’s plot, a transfer coefficient, α = 0.45, and an electron transfer rate constant, k s  = 10.5 s−1, for the electron transfer of the couple R-NO/R-NHOH, were calculated. This redox reaction results to be a very efficient mediator for electrocatalytic NADH oxidation. The 35DNB-MWCNTGC electrode efficiently catalyzes the oxidation of NADH with a decrease of more than 0.60 V vs Ag/AgCl in the overpotential compared to the bare GCE and a difference of 0.25 V vs Ag/AgCl with respect to the situation without mediator. The preparation of the electrode is very easy and not time-consuming. Graphical abstract The precursor 3,5-dinitrobenzoic acid entrapped on the MWCNTs three dimensional array generate the redox couple RNO/RNHOH capable to act as mediator in the oxidation of NADH.
      PubDate: 2016-08-15
      DOI: 10.1007/s12678-016-0323-0
  • OER Activity of Ir-Ta-Zr Composite Anode as a Counter Electrode for
           Electrohydrogenation of Toluene
    • Authors: Kohei Nagai; Kensaku Nagasawa; Shigenori Mitsushima
      Abstract: 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 Abstract 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
  • Platinum Nanoparticles Supported on Nitrogen-Doped Graphene Nanosheets as
           Electrocatalysts for Oxygen Reduction Reaction
    • Authors: Kristel Jukk; Nadezda Kongi; Protima Rauwel; Leonard Matisen; Kaido Tammeveski
      Abstract: Abstract This paper deals with nitrogen-doped graphene nanosheets prepared using dicyandiamide precursor as a catalyst support for oxygen reduction reaction (ORR). Platinum nanoparticles supported on N-doped graphene nanosheets (Pt/NG) were studied as electrocatalysts for ORR in acid and alkaline solutions employing the rotating disk electrode (RDE) technique. Pt/NG nanomaterials were synthesised by chemical reduction of hexachloroplatinic acid using sodium borohydride or ethylene glycol as reducing agents. Surface morphology and composition of the prepared catalysts were examined by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a high dispersion of Pt nanoparticles on N-doped graphene nanosheets due to strong interaction of Pt with nitrogen functionalities. The average nitrogen content was between 6 and 7 at.% according to the XPS analysis. In acidic solution, 20 wt% Pt/NG catalyst prepared by borohydride reduction showed the highest specific activity for O2 reduction from all the Pt/NG materials studied. Pt/NG nanomaterials exhibited excellent electrocatalytic activity in alkaline media, and their half-wave potentials were similar to that of commercial Pt/C catalyst. The RDE data analysis showed that the ORR on the Pt/NG catalysts proceeded via four-electron pathway. Graphical Abstract ᅟ
      PubDate: 2016-07-30
      DOI: 10.1007/s12678-016-0322-1
  • A Facile Synthesis of Size-Controllable IrO 2 and RuO 2 Nanoparticles for
           the Oxygen Evolution Reaction
    • Authors: Tam D. Nguyen; Günther G. Scherer; Zhichuan J. Xu
      Abstract: The efficiency of the water electrolysis process is restricted by the sluggish kinetics of the oxygen evolution reaction (OER). Developing efficient catalysts and their synthesis methods is highly desired to improve the kinetics of the OER and therefore the overall efficiency of the water electrolysis. In this report, we present a facile wet-chemical method for synthesizing IrO2 and RuO2 nanoparticles (NPs) for the OER. The nanoparticles were synthesized by reducing metal chlorides in ethylene glycol in the presence of polyvinylpyrrolidone, followed by annealing in air. The particle size was controlled by adjusting the annealing temperature. The activity of IrO2 and RuO2 NPs supported on carbon black was investigated by cyclic voltammetry (CV) in alkaline (0.1 M KOH) electrolyte. As-synthesized IrO2 and RuO2 NPs showed high OER activity. The IrO2 NPs exhibited a specific activity of up to 3.5 (±1.6) μA/cm2 oxide at 1.53 V (vs. RHE), while the RuO2 NPs achieved a value of 124.2 (±8) μA/cm2 oxide. Moreover, RuO2 NPs showed a mass activity for OER, up to 102.6 (±10.5) A/goxide at 1.53 V (vs. RHE), which represents the highest value reported in the literature to date. Graphical abstract A facile wet-chemical method for synthesizing IrO2 and RuO2 nanoparticles (NPs) is reported here. The nanoparticles were synthesized by reducing metal chlorides in ethylene glycol in the presence of polyvinylpyrrolidone, followed by annealing in air. The size of particles can be controlled by varying the annealing temperature and subsequently their OER activities are varied
      PubDate: 2016-06-30
      DOI: 10.1007/s12678-016-0321-2
  • Fabrication of β-Cyclodextrin-Functionalized Reduced Graphene Oxide and
           Its Application for Electrocatalytic Detection of Carbendazim
    • Authors: Tien Song Hiep Pham; Li Fu; Peter Mahon; Guosong Lai; Aimin Yu
      Abstract: Abstract We reported a graphene-based electrochemical sensor for sensitively measuring carbendazim, which is one of the effective benzimidazole fungicides popularly used in agriculture. The β-cyclodextrin-functionalized reduced graphene oxide (β-CD–RGO) nanocomposites were synthesized using hydrazine as the reducing agent at room temperature. The as-synthesized nanocomposites were characterized using different analytical methods including UV–visible spectroscopy and Fourier transform infrared spectroscopy. The nanocomposites with a combination of physicochemical properties of RGO and high molecular recognition capability of β-CD were used to modify the surface of a glassy carbon electrode for the electrochemical determination of the drug carbendazim using cyclic voltammetry and differential pulse voltammetry. The current responses of carbendazim on the β-CD–RGO-modified electrode were greatly enhanced compared to that on the bare electrode due to the electrocatalytic effect of β-CD–RGO. It was found that the peak currents increased linearly with the carbendazim concentration in the range between 0.1 and 40 μM. The obtained results suggest that β-CD–RGO composite could be a potential candidate for the preparation of effective electrochemical sensors for carbendazim or similar drugs in the future. Graphical Abstract A sensitive electrochemical sensor of carbendazim was developed based on the electro-catalysis of β-CD/reduced graphene oxide modified electrode.
      PubDate: 2016-06-22
      DOI: 10.1007/s12678-016-0320-3
  • Pt 3 M (M: Co, Ni and Fe) Bimetallic Alloy Nanoclusters as Support-Free
           Electrocatalysts with Improved Activity and Durability for Dioxygen
           Reduction in PEM Fuel Cells
    • Authors: B. Narayanamoorthy; V. Linkov; C. Sita; S. Pasupathi
      Abstract: Abstract Pt3M (M: Co, Ni and Fe) bimetallic alloy nanoclusters were synthesized by a novel and simple chemical reduction approach, and employed as the promising electrocatalyst to accelerate the kinetics of oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells. From XRD, the positive shift of diffraction angle confirms the alloy formation between Pt and M and the elemental composition was confirmed by energy dispersive X-ray spectroscopy analysis. The nanocluster morphology and particle size was determined using scanning and transmission electron microscopy analysis. The ORR kinetic parameters for Pt-M electrocatalysts were calculated and compared with reported Pt/C catalysts. Among the Pt-M electrocatalysts, Pt-Co was found to be the most efficient catalyst having the higher mass and specific activity (at 0.9 V vs. RHE) of 0.44 mA/μg and 0.69 mA/cm2, respectively. The accelerated durability test reveals that the Pt-M bimetallic alloy nanoclusters retain appreciable surface area and mass activity after 8000 potential cycles confirms good long-term durability, and also competing with the reported benchmark ORR catalysts. Graphical Abstract TEM image of Pt3Co bimetallic alloy nanocluster with cyclic voltammograms of Pt3M (M: Co, Ni & Fe) electrocatalysts
      PubDate: 2016-06-10
      DOI: 10.1007/s12678-016-0318-x
  • Regulating the Product Distribution of CO Reduction by the Atomic-Level
           Structural Modification of the Cu Electrode Surface
    • Authors: Youn-Geun Kim; Alnald Javier; Jack H. Baricuatro; Manuel P. Soriaga
      Abstract: Abstract Cu catalyzes the electrochemical reduction of CO2 or CO to an assortment of products, a behavior that is a detriment when only one reduced compound is desired. The present article provides an example in which, through the atomic-level control of the structure of the Cu electrode surface, the yield distribution is regulated to generate only one product. The reaction investigated was the preferential reduction of CO to C2H5OH on Cu at a low overpotential in alkaline solution. Experimental measurements combined electrochemical scanning tunneling microscopy (ECSTM) and differential electrochemical mass spectrometry (DEMS). An atomically ordered Cu(100) surface, prepared from either a single crystal or by Cu(pc)-to-Cu(100) reconstruction, did not produce ethanol. When the surfaces were subjected to monolayer-limited Cu↔Cu2O cycles, only the reconstructed surface underwent an additional structural transformation that spawned the selective production of ethanol at a potential 645 mV lower than that which generates multiple products. Quasi-operando ECSTM indicated transformation to an ordered stepped surface, Cu(S) − [3(100) × (111)], or Cu(511). The non-selective, multiple-product Cu-catalyzed reduction of CO had thus been regulated to yield only one liquid fuel by an atomic-level structural modification of the electrode surface. Graphical Abstract TOC GRAPHIC
      PubDate: 2016-06-07
      DOI: 10.1007/s12678-016-0314-1
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