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FORTH, Greece

Jaksic J.M.,ICEHT | Labou D.,ICEHT | Labou D.,University of Belgrade | Papakonstantinou G.D.,ICEHT | And 2 more authors.
Journal of Physical Chemistry C | Year: 2010

New striking prospects both in low and medium temperature polymer electrolyte membrane fuel cell (PEMFC) and in water electrolysis (WE) have been opened by the interactive supported individual (Pt) or prevailing hyper-d-electronic nanostructured metal clusters (WPt3, NbPt 3, HfPd3, ZrNi3), grafted upon and within high altervalent capacity hypo-d-oxides (WO3, NbO2, TaO 2, TiO2) and their proper mixed valence compounds, to create a novel type of alternating polarity (alterpolar) interchangeable composite electrocatalysts for hydrogen and oxygen electrode reactions. Whereas in aqueous media Pt (Pt/C) features either chemisorbed catalytic surface properties of Pt-H or Pt=O, missing any effusion of other interacting species, a new generation of composite SMSI (strong metal-support interaction) electrocatalysts in condensed wet state primarily characterizes interchangeable extremely fast reversible spillover of either H-adatoms or the primary oxides (Pt-OH, Au-OH) or the invertible bronze type behavior of these significant interactive electrocatalytic ingredients. Altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3) under cathodic and/or its hydrated state (Pt/W(OH)6), responsible for Pt-OH effusion, under anodic polarization, this way establishing instantaneous reversibly revertible alterpolar bronze features (Pt/H0.35WO3 ⇔ Pt/W(OH)6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured type electrocatalysts, even of mixed hypo-d-oxide structure (Pt/H 0.35WO3/TiO2/C, Pt/HxNbO 3/TiO2/C), have for the first time been synthesized by the sol-gel methods and shown rather high stability, electron conductivity and nonexchanged initial pure monobronze spillover and catalytic properties. Such a unique electrocatalytic system, as the striking target issue of the present paper, has been shown to be the superior substantiation of the revertible cell assembly for spontaneous reversible alterpolar interchanges between PEMFC and WE. The underpotential spillover double layer charging and discharging properties of the primary oxide (M-OH), interrelated with the interactive self-catalytic effect of dipoleoriented water molecules, has also been pointed out. © 2010 American Chemical Society.

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