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Posted: May 27, 2014

Tantalum oxide nanoparticles based Pt nanoparticles as efficient catalysts for polymer electrolyte fuel cells

(Nanowerk News) One of the challenges for the commercialization of polymer electrolyte fuel cells (PEFCs) is the development of new cathode catalysts for the oxygen reduction reaction (ORR) that exhibit superior activity and durability than conventional platinum (Pt) catalysts (Pt/C).
Here, Zaenal Awaludin, Takeo Ohsaka, and colleagues at Department of Electronic Chemistry report the development of TaOx (tantalum oxide) nanoparticles-capped Pt nanoparticles (Pt/TaOx) that possess a higher activity and durability than a Pt catalyst alone ("TaOx-capped Pt nanoparticles as active and durable electrocatalysts for oxygen reduction").
TaO<span class='subscript' style=x-capped Pt nanoparticle within a TaOx framework" border="0" align="middle">
Schematic illustrations of (a) TaOx-capped Pt nanoparticle within a TaOx framework, (b) bonding formation of Ta with GC and Pt, and (c) O2 adsorption on Pt-TaOx surface.
The Pt/TaOx catalyst has a unique structure comprising of a TaOx-capped Pt nanoparticles. The Pt/TaOx structures were prepared by electrodeposition of TaOx nanoparticles followed by Pt nanoparticles on glassy carbon (GC) electrodes.
The electrochemically active surface area (ECAS) of the TaOx-capped Pt nanoparticles catalyst is about one-fourth of that of the Pt/C , but its ORR activity is almost comparable to that of the Pt/C and its durability is about 8 times higher compared with the Pt/C.
 Pt/TaO<span class='subscript' style=x catalyst on GC electrode" border="0" align="middle">
Cross sectional images of SEM (a, b) and BSEM (c) of Pt/TaOx catalyst on GC electrode.
The unique assembly of the TaOx-capped Pt nanoparticles catalyst in which the Pt nanoparticles are dimensionally stabilized by the porous TaOx framework could prevent the Pt nanoparticles from aggregation and dissolution. The enhanced ORR activity is ascribed to factors that include a favorable adsorption of O2 molecules for 4e-ORR as a result of a spillover effect which may alleviate the poisoning effect of OHad species on the Pt surface; lowering the local pH in the vicinity of Pt nanoparticles; and electronic interaction between Pt nanoparticles and TaOx.
The TaOx-capped Pt nanoparticles have a dimensionally stable structure and expected to be a promising electrocatalyst for ORR in PEFCs.
Source: Tokyo Institute of Technology
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