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Spectroscopic Evidence of Platinum Negative Oxidation States at Electrochemically Reduced Surfaces

Abstract : Electrochemical "reduction" of Pt was investigated using electrochemical and X-ray photoelectron spectroscopy (XPS) techniques. This transformation of a platinum metal, which is possible with a large variety of organic and inorganic cations, was investigated in DMF containing CsI salts chosen as a test system. Experiments show that considerable modifications of the chemical nature of the starting material accompany the morphological changes that were previously reported. With rather mild reduction conditions, cesium-platinides-like structures were detected. XPS investigations bring a direct spectroscopic evidence for the formation of a reduced platinum state from a metallic electrode held at a negative potential. XPS spectra clearly showed a significant and continuous shift of the Pt formal oxidation degree with the injected charge of -1.6. This behavior is analogous to a charging process. Additionally, proofs of the full reversibility of the phenomenon was provided by the XPS analyses showing that the "reduced Pt" returns to its metallic state after reaction with a diazonium salt. It is noticeable that the formation of negative oxidation state of Pt exists even when a large competitive electrochemical process occurs, as in our case with the reduction of protons from residual water.
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Submitted on : Tuesday, November 20, 2007 - 11:08:24 AM
Last modification on : Wednesday, April 7, 2021 - 3:18:07 PM

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Jalal Ghilane, Maryline Guilloux-Viry, Philippe Hapiot, Jacques Simonet, Corinne Lagrost, et al.. Spectroscopic Evidence of Platinum Negative Oxidation States at Electrochemically Reduced Surfaces. Journal of Physical Chemistry C, American Chemical Society, 2007, 111, pp.5701-5707. ⟨10.1021/jp068879d⟩. ⟨hal-00189100⟩



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