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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]
  • 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: 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 Abstract 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: 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 Abstract 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: 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 Abstract 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: 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 Abstract 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: 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 Abstractᅟ 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: 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 Abstract 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: 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 Abstract 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: 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 Abstract Optimising ECL Production Through Careful Selection of Co-Reactions Based on Energetics Involved
      PubDate: 2016-11-02
      DOI: 10.1007/s12678-016-0338-6
  • Facile One Pot Synthesis of CuO Nanostructures and Their Effect on
           Nonenzymatic Glucose Biosensing
    • Authors: Mohit Chawla; Veerender Sharma; Jaspreet Kaur Randhawa
      Abstract: 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 Abstract Schematic illustrating the synthesis and glucose sensing experiments of CuO nanostructures.
      PubDate: 2016-10-27
      DOI: 10.1007/s12678-016-0337-7
  • 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
      Abstract: 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 Abstract Nickel hydroxide nanoflakes (Ni(OH)2-NF) catalyst for the electrochemical oxidation of urea in alkaline solution.
      PubDate: 2016-10-22
      DOI: 10.1007/s12678-016-0336-8
  • 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
  • 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
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