In situ Spectroelectrochemical Investigation of Pt(II/IV) Oxidation in Aqueous Solution Using X-ray Absorption Spectroscopy

The oxidation from PtIICl42− to PtIVCl62− in HCl aq. was studied in situ by combining electrochemistry with XAFS spectroscopy. During the oxidation of PtIICl42−, isosbestic points were observed in Pt LIII and LII XANES spectra as a function of time, indicating that the Pt(II/IV) redox equilibrium is the only reaction in the system. The Pt LIII and LII X-ray absorption edge energies of the initial PtIICl42− are 11562.9 and 13271.8 eV, respectively, while those of the electrolyzed species are 11564.6 and 13273.7 eV which are identical with those of a PtIVCl62– reference sample. The coordination of the electrolyzed species was characterized by structural parameters derived from the EXAFS curve fit, and identified to PtIVCl62–.