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Abstract: This paper is focused on the in situ radiotracer and voltammetric studies of the induced HSO4 −/SO4 2− adsorption at Pt(poly) and Pt(111) surfaces in 0.1moldm−3 HClO4 solution in the course of Cr(VI) electroreduction. Besides this, the sorption behavior of HSO4 −/SO4 2− ions on bare Pt(poly) and Pt(111) electrodes is compared and discussed. From the experimental results it can be stated that: (i) although the extent of bisulfate/sulfate adsorption is strongly dependent upon the crystallographic orientation of Pt surfaces, the maximum coverage on the Pt(111) does not exceed 0.2 monolayer; (ii) the Cr(VI) electroreduction on both poly- and (111) oriented platinum proceeds via a ce (chemical-electron-transfer) mechanism to yield Pt surfaces covered with intermediate surface adlayers containing Cr(VI) particles (and reduced Cr-containing adspecies) and ‘strongly bonded’ HSO4 −/SO4 2− ions; (iii) while the coverage of platinum surfaces by the intermediate complexes formed in the course of Cr(VI) electroreduction at E >0.20V is basically independent of the crystallographic orientation of the Pt electrode, the onset for rapid Cr(VI) reduction is highly affected by the nature and crystallographic orientation of the electrode. [Copyright &y& Elsevier]

Highlights: [•] Porous Pt layers were electroplated for radioelectrochemical measurements. [•] The theoretical relationships describing the porous electrode have been validated. [•] Surface excess of the chloride ions as a function of the potential could be measured. [•] Saturation time of the porous layers could be quantitatively estimated. [•] Mobility of the adsorbed chloride ions have been tested. [ABSTRACT FROM AUTHOR]

Highlights: [•] The basis of a new radielectrochemical method with porous electrode was described. [•] The relationship for the radiation intensity vs. surface excess function was given. [•] The parameters were optimized for the platinum black/36Cl chloride ion system. [•] The proper thickness of the infinitely thin porous layer was calculated. [ABSTRACT FROM AUTHOR]