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Nenad M Markovic - One of the best experts on this subject based on the ideXlab platform.

  • oxygen reduction on silver low index single crystal surfaces in Alkaline Solution rotating ring disk ag hkl studies
    Journal of Physical Chemistry B, 2006
    Co-Authors: Berislav Blizanac, P N Ross, Nenad M Markovic
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring−disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1M KOH increased in the sequence (100) < (110) < (111) for both oxygen and peroxide reduction. These differences are attributed to the structure sensitivity of hydroxyl anion (OH-) adsorption on Pt(hkl) and its inhibiting (site blocking) effect on oxygen kinetics. Two different types of OHads occur on Pt(100) and Pt(110), a reversible OHrv, and an irreversible OHir, while only the reversible form is formed on Pt(111). Very small fluxes (I R/N ≪ 0.01I D) of peroxide were detected at the ring at potentials where the surfaces have only the reversible form of OHads. More peroxide (I R/N < 0.03I D) was found with the Pt(100) and Pt(110)surfaces in the potential region where irreversible adsorption occurs. The mechanism of O2 reduction was also affected by adsorbed hydrogen with increased formation of per...

  • oxygen reduction on platinum low index single crystal surfaces in Alkaline Solution rotating ring diskpt hkl studies
    Journal of Physical Chemistry B, 2006
    Co-Authors: Berislav Blizanac, P N Ross, Nenad M Markovic
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring−disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1M KOH increased in the sequence (100) < (110) < (111) for both oxygen and peroxide reduction. These differences are attributed to the structure sensitivity of hydroxyl anion (OH-) adsorption on Pt(hkl) and its inhibiting (site blocking) effect on oxygen kinetics. Two different types of OHads occur on Pt(100) and Pt(110), a reversible OHrv, and an irreversible OHir, while only the reversible form is formed on Pt(111). Very small fluxes (I R/N ≪ 0.01I D) of peroxide were detected at the ring at potentials where the surfaces have only the reversible form of OHads. More peroxide (I R/N < 0.03I D) was found with the Pt(100) and Pt(110)surfaces in the potential region where irreversible adsorption occurs. The mechanism of O2 reduction was also affected by adsorbed hydrogen with increased formation of per...

  • oxygen reduction of platinum low index single crystal surfaces in Alkaline Solution rotating ring disk sub pt hkl studies
    The Journal of Physical Chemistry, 1996
    Co-Authors: Nenad M Markovic, Hubert A Gasteiger, P N Ross
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring-disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1 M KOH increased in the sequence (100) (100)more » > (110). 34 refs., 6 figs.« less

P N Ross - One of the best experts on this subject based on the ideXlab platform.

  • oxygen reduction on platinum low index single crystal surfaces in Alkaline Solution rotating ring diskpt hkl studies
    Journal of Physical Chemistry B, 2006
    Co-Authors: Berislav Blizanac, P N Ross, Nenad M Markovic
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring−disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1M KOH increased in the sequence (100) < (110) < (111) for both oxygen and peroxide reduction. These differences are attributed to the structure sensitivity of hydroxyl anion (OH-) adsorption on Pt(hkl) and its inhibiting (site blocking) effect on oxygen kinetics. Two different types of OHads occur on Pt(100) and Pt(110), a reversible OHrv, and an irreversible OHir, while only the reversible form is formed on Pt(111). Very small fluxes (I R/N ≪ 0.01I D) of peroxide were detected at the ring at potentials where the surfaces have only the reversible form of OHads. More peroxide (I R/N < 0.03I D) was found with the Pt(100) and Pt(110)surfaces in the potential region where irreversible adsorption occurs. The mechanism of O2 reduction was also affected by adsorbed hydrogen with increased formation of per...

  • oxygen reduction on silver low index single crystal surfaces in Alkaline Solution rotating ring disk ag hkl studies
    Journal of Physical Chemistry B, 2006
    Co-Authors: Berislav Blizanac, P N Ross, Nenad M Markovic
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring−disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1M KOH increased in the sequence (100) < (110) < (111) for both oxygen and peroxide reduction. These differences are attributed to the structure sensitivity of hydroxyl anion (OH-) adsorption on Pt(hkl) and its inhibiting (site blocking) effect on oxygen kinetics. Two different types of OHads occur on Pt(100) and Pt(110), a reversible OHrv, and an irreversible OHir, while only the reversible form is formed on Pt(111). Very small fluxes (I R/N ≪ 0.01I D) of peroxide were detected at the ring at potentials where the surfaces have only the reversible form of OHads. More peroxide (I R/N < 0.03I D) was found with the Pt(100) and Pt(110)surfaces in the potential region where irreversible adsorption occurs. The mechanism of O2 reduction was also affected by adsorbed hydrogen with increased formation of per...

  • oxygen reduction of platinum low index single crystal surfaces in Alkaline Solution rotating ring disk sub pt hkl studies
    The Journal of Physical Chemistry, 1996
    Co-Authors: Nenad M Markovic, Hubert A Gasteiger, P N Ross
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring-disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1 M KOH increased in the sequence (100) (100)more » > (110). 34 refs., 6 figs.« less

  • hydrogen electrochemistry on platinum low index single crystal surfaces in Alkaline Solution
    Journal of the Chemical Society Faraday Transactions, 1996
    Co-Authors: Nenad M Markovica, Hubert A Gasteiger, Stella T Sarraf, P N Ross
    Abstract:

    The results of a study of the hydrogen reaction (HER) and the hydrogen oxidation reaction (HOR) on the three low-index faces of Pt in Alkaline Solution are presented. The study features a new method for the use of Pt single crystals in a rotating disk electrode (RDE) configuration. At low negative overpotentials, the order of activity for the HER increased in the sequence (111) < (100) < (110). At low positive overpotentials, the order of activity for the HOR increased in the sequence (111)≈(100)(110). These differences in activity with crystal face are attributed to different states of adsorbed hydrogen and to different effects of these states on the mechanism of the hydrogen reaction. Two different types of adsorbed hydrogen are observed on Pt(hkl) surfaces. A high binding energy state, often referred to as underpotential deposited hydrogen, Hupd, has an inhibiting (site blocking) effect on the rate of the HER and HOR. A low binding energy state is a reaction intermediate at low overpotentials in both the HOR as well as the HER, and is most prevalent on the (110) surface. At high positive overpotentials, in the potential region where adsorption of hydroxy species (OHad) occurs, the effects of surface crystallography on the HOR is attributed to the structural sensitivity of the adsorption of OHad on Pt(hkl), with OHad having an inhibiting effect on the HOR, the inhibition decreasing in the sequence (100)(110) < (111).

Matthieu Horgnies - One of the best experts on this subject based on the ideXlab platform.

  • polymeric microstructures induced by freeze drying process comparative study of ps41 paa 271 morphologies after impregnations in water and in an Alkaline Solution
    Journal of Materials Processing Technology, 2009
    Co-Authors: Matthieu Horgnies
    Abstract:

    Surface of polymeric coating can be modified after being submitted to treatment based oil freeze-drying. Morphology of polystyrene-b-poly(acrylic acid) (PS41 -PAA(271)) diblock copolymers was investigated by using scanning electron microscopy (SEM). After clip-coating oil stainless steel substrate, influences of the nature and the pH of the immersing liquid, used before freeze-drying, were established. If water has impregnated the polymer in order to form a hydrogel, the surface could acquire a cellular monolayer structure after freeze-drying while stretched polymeric nodules, affected by the conditions of sublimation, cover some other parts of the surface. The porous monolayer happens when freeze-drying occurs in a homogenous and well-crystallised icy material. Observations of nucleation sites linked by polymeric filaments could be considered as the first step of growth of this regular network. In the other hand, if a KOH Alkaline Solution has impregnated the polymer before freeze-drying, ionic species affect the morphology by inducing specific lamellar structures that close the porous Structure. XPS analyses highlight that the carboxylic functions of PS-PAA coating could be deprotonated during the immersion in the Alkaline Solution. This deprotonation induces polyacrylate-based compounds that Could disturb the growth of the cellular polymeric network. This phenomenon Should be avoided by using a neutral immersing Solution in order to obtain a homogenous and Porous monolayer of PS-PAA after freeze-drying. (C) 2009 Elsevier B.V. All rights reserved.

  • polymeric microstructures induced by freeze drying process comparative study of ps41 paa 271 morphologies after impregnations in water and in an Alkaline Solution
    Journal of Materials Processing Technology, 2009
    Co-Authors: Matthieu Horgnies
    Abstract:

    Surface of polymeric coating can be modified after being submitted to treatment based oil freeze-drying. Morphology of polystyrene-b-poly(acrylic acid) (PS41 -PAA(271)) diblock copolymers was investigated by using scanning electron microscopy (SEM). After clip-coating oil stainless steel substrate, influences of the nature and the pH of the immersing liquid, used before freeze-drying, were established. If water has impregnated the polymer in order to form a hydrogel, the surface could acquire a cellular monolayer structure after freeze-drying while stretched polymeric nodules, affected by the conditions of sublimation, cover some other parts of the surface. The porous monolayer happens when freeze-drying occurs in a homogenous and well-crystallised icy material. Observations of nucleation sites linked by polymeric filaments could be considered as the first step of growth of this regular network. In the other hand, if a KOH Alkaline Solution has impregnated the polymer before freeze-drying, ionic species affect the morphology by inducing specific lamellar structures that close the porous Structure. XPS analyses highlight that the carboxylic functions of PS-PAA coating could be deprotonated during the immersion in the Alkaline Solution. This deprotonation induces polyacrylate-based compounds that Could disturb the growth of the cellular polymeric network. This phenomenon Should be avoided by using a neutral immersing Solution in order to obtain a homogenous and Porous monolayer of PS-PAA after freeze-drying. (C) 2009 Elsevier B.V. All rights reserved.

Berislav Blizanac - One of the best experts on this subject based on the ideXlab platform.

  • oxygen reduction on platinum low index single crystal surfaces in Alkaline Solution rotating ring diskpt hkl studies
    Journal of Physical Chemistry B, 2006
    Co-Authors: Berislav Blizanac, P N Ross, Nenad M Markovic
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring−disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1M KOH increased in the sequence (100) < (110) < (111) for both oxygen and peroxide reduction. These differences are attributed to the structure sensitivity of hydroxyl anion (OH-) adsorption on Pt(hkl) and its inhibiting (site blocking) effect on oxygen kinetics. Two different types of OHads occur on Pt(100) and Pt(110), a reversible OHrv, and an irreversible OHir, while only the reversible form is formed on Pt(111). Very small fluxes (I R/N ≪ 0.01I D) of peroxide were detected at the ring at potentials where the surfaces have only the reversible form of OHads. More peroxide (I R/N < 0.03I D) was found with the Pt(100) and Pt(110)surfaces in the potential region where irreversible adsorption occurs. The mechanism of O2 reduction was also affected by adsorbed hydrogen with increased formation of per...

  • oxygen reduction on silver low index single crystal surfaces in Alkaline Solution rotating ring disk ag hkl studies
    Journal of Physical Chemistry B, 2006
    Co-Authors: Berislav Blizanac, P N Ross, Nenad M Markovic
    Abstract:

    The first results of a study of the oxygen reduction reaction on a rotating ring−disk electrode using single-crystal Pt disk electrodes in Alkaline Solution are presented. The order of activity of Pt(hkl) in 0.1M KOH increased in the sequence (100) < (110) < (111) for both oxygen and peroxide reduction. These differences are attributed to the structure sensitivity of hydroxyl anion (OH-) adsorption on Pt(hkl) and its inhibiting (site blocking) effect on oxygen kinetics. Two different types of OHads occur on Pt(100) and Pt(110), a reversible OHrv, and an irreversible OHir, while only the reversible form is formed on Pt(111). Very small fluxes (I R/N ≪ 0.01I D) of peroxide were detected at the ring at potentials where the surfaces have only the reversible form of OHads. More peroxide (I R/N < 0.03I D) was found with the Pt(100) and Pt(110)surfaces in the potential region where irreversible adsorption occurs. The mechanism of O2 reduction was also affected by adsorbed hydrogen with increased formation of per...

Kaido Tammeveski - One of the best experts on this subject based on the ideXlab platform.

  • electrocatalytic oxygen reduction on silver nanoparticle multi walled carbon nanotube modified glassy carbon electrodes in Alkaline Solution
    Electrochemistry Communications, 2012
    Co-Authors: Lauri Tammeveski, Väino Sammelselg, Heiki Erikson, Ave Sarapuu, Jekaterina Kozlova, Peeter Ritslaid, Kaido Tammeveski
    Abstract:

    Abstract The electrochemical reduction of oxygen was studied on Ag nanoparticle/multi-walled carbon nanotube (AgNP/MWCNT) nanocomposites in Alkaline Solution employing the rotating disk electrode (RDE) method. The composite material was prepared by sputter deposition of Ag catalyst on the surface of MWCNTs. The surface morphology of the AgNP/MWCNT composites was examined by scanning electron microscopy (SEM). The SEM images show that there is a wide size distribution of Ag particles on MWCNTs. The RDE results reveal a high electrocatalytic activity of the AgNP/MWCNT nanocomposites towards the oxygen reduction reaction (ORR). On these catalysts the ORR proceeds by a four-electron pathway. The AgNP/MWCNT composite is a good catalyst for peroxide reduction. The results obtained are important for the development of Ag-based catalysts for Alkaline membrane fuel cells.

  • electroreduction of oxygen on multi walled carbon nanotubes modified highly oriented pyrolytic graphite electrodes in Alkaline Solution
    Journal of Electroanalytical Chemistry, 2006
    Co-Authors: Gea Jurmann, Kaido Tammeveski
    Abstract:

    Abstract The electrochemical reduction of oxygen has been studied on multi-walled carbon nanotubes (MWCNTs) modified highly oriented pyrolytic graphite (HOPG) electrodes in 0.1 M KOH Solution using the rotating disk electrode (RDE) technique. The oxygen reduction behaviour of MWCNTs/HOPG electrodes of various modifications was compared. Electrochemical studies indicate that the MWCNTs/HOPG electrodes show a remarkable electrocatalytic activity towards O 2 reduction in Alkaline media. The number of electrons transferred per O 2 molecule was a function of potential and it increased up to four at high negative potentials. The O 2 reduction behaviour of MWCNTs/HOPG electrodes using oxidatively treated MWCNTs was also studied. The oxidative pre-treatment of MWCNTs did not change their electrocatalytic properties for oxygen reduction in Alkaline Solution to a noticeable degree.