| Abstract
| - An XAS investigation was undertaken to understand the mechanism of our platinum deposition process. Thisprocess is based on H2PtCl6 impregnation onto activated carbon followed by current pulses reduction. Aftereach step of the process and during the electrochemical reduction, ex situ and in situ dispersive X-ray absorptionmeasurements allowed us to follow the evolution of platinum environment and its valence state. Thischaracterization shows a first diminution in the electronic density of final states for Pt atoms when H2PtCl6is involved in the impregnation mixture, because of the simple contact of this acid with activated carbon.After the impregnation mixture spraying step onto a carbon support and thermal treatment, the platinumcompound is found to be reduced to a Pt(II) form corresponding to the anionic PtCl42- complex. Theelectrochemical reduction takes place in the first galvanostatic pulses. The competitive proton evolution tohydrogen on in situ generated metallic platinum particles occurs, but EXAFS analysis shows that, in ourprocess, this evolved hydrogen does not have a major role in platinum species reduction.
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