Electrochemistry of chemisorbed molecules. III. Determination of the oxidation state of halides chemisorbed on platinum. Reactivity and catalytic properties of adsorbed species

Abstract

Publication costs assisted by the National Science Foundation and the Petroleum Research Fund Thin layer voltammetric data for Pt electrodes indicate that F", Cl", Br", and I~form chemisorbed layers which withstand rinsing with typical aqueous electrolytes. The chemisorbed halides are much less reactive toward electrochemical oxidation than the corresponding dissolved ions. Aqueous I" reacts with the Pt surface to form an uncharged adsorbed species, whereas F", Cl", and Br™ are adsorbed in anionic form. Accordingly, F~, Cl", and Br", but not I, induce the adsorption of Fe2+ in a 2:1 ratio of halide to iron. The influence of adsorbed halide on electrode reactions of metal ions such as Pt(II), Pt(IV), Sb(III), and Sb(V) can be understood simply in terms of electrostatic interaction between the reactant and the electrode surface. Chemisorbed F", Cl", and Br" cause the surface to be less positively charged, whereas chemisorbed I has the opposite effect. In the irreversibly chemisorbed form, halide does not serve as an electron transfer bridge in the oxidation of Pt(II) or Sb(III).

Voltammetric Characterization of trans-Dioxo Ethylenediamine Complexes of Re(V) in Aqueous Solutions

“…When E sa = 0.85 V, anodic and cathodic current peaks at ca. 0.5 V, corresponding to the electrochemical response of I 2(aq) /I − (aq) (14) and I ads /I − (aq) redox couples (15)(16)(17)(18) are observed. Iodine adsorption is reported in the literature and adlayer I species are well characterized by quartz crystal microbalance, LEED, and STM studies (15-18).…”

Redox Behavior of Re(V)–Amino Acid Containing Complexes

“…Current peaks at 1.23 and 1.36 V correspond both to I ad oxidation and to O-electrosorption (6,(12)(13)(14). Once E sa reaches a value of 1.55 V, the subsequent negative-going potential scan exhibits a cathodic current peak at 0.74 V related to O-electrodesorption and to IO − 3(aq) electroreduction (6,12,13), whereas the cathodic current peak at 0.48 V is associated with the electroreduction of I-containing species (6)(7)(8)(9)(10)(11).…”

Four potential step differential amperometry in a single pulse sequence mode

“…For a solid electrode and adsorption system like the adsorption of dopamine or chloride ion on Pt electrodes [16,17], Eo can be set at a reducing or oxidizing potential to facilitate the electrode cleaning and prevent the contamination of the electrode.…”