Publication de David Riassetto 2017

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"tAn electron-conducting metal-oxide substrate must fulfill three criteria to represent a viable alternativeto conventional carbon blacks used as supports for Pt-based nanoparticles in proton-exchange membranefuel cell (PEMFC): (i) be electron-conducting, (ii) be corrosion resistant and (iii) possess an opened porousstructure compatible with facile ionomer insertion and efficient mass-transport properties. Using a sol-gel route, antimony-doped tin dioxide (Sb-doped SnO2, ATO) aerogels with such characteristics weresynthesized: an optimal Sb content of 10 at.% was found in terms of specific surface area and electricalconductivity. Pt nanoparticles were loaded onto 10 at.% Sb-doped SnO2(Pt/ATO),undoped SnO2(Pt/SnO2)and Vulcan XC72 (Pt/C) via a modified polyol route, and their electrocatalytic activity for the oxygenreduction reaction (ORR) was evaluated. A 2-fold enhancement in ORR specific activity was measuredon Pt/ATO over Pt/C. An accelerated stress test (AST) protocol, mimicking start-up/shutdown events ina PEMFC, was used to determine the long-term ORR performance of the Pt/ATO and the reference Pt/Celectrocatalysts. The carbon support was not robust enough in these harsh conditions, as observed fromthe massive detachment of Pt nanoparticles from Vulcan XC72. On the contrary, the Pt nanoparticles didnot detach from the ATO support. However, a core@shell structure with a Sb-poor surface covering a corefeaturing a Sb content close to the nominal formed during the AST. This core@shell structure restrictedthe capacity of the Pt nanoparticles to exchange electrons, as evidenced by the attenuated Pt surfaceoxide formation/reduction features, and led to decreased catalytic activity for the ORR"