DPT modeling of Stark-Tuning effect : CO on polarized Pd(100) as a probe for double-layer electrostatic effects in electrochemistry

• The lifetime of chemisorbed radical anions produced in the electroreduction of vinylic molecules is thought to play a decisive part in the mechanism accounting for the production of grafted films in electropolymerization reactions. With the ultimate purpose of evaluating these lifetimes, we propose a one-dimensional model taking into account the interface bond, the anion/metallic surface image charge potential, and the anion/polarized-surface electrostatic repulsion. Orders of magnitude are known for the parameters entering in these terms, except for the latter. In the present work, this term is described using the Gouy-Chapmann model for the electrochemical double layer. Comparing our theoretical DFT predictions on Stark-Tuning effect of CO on Pd(100) with experiment, we can discuss on the legitimacy of a phenomenological linear relationship between the (microscopic) surface electric field and the (macroscopic) electrode potential. The slope of this relationship, termed the electric field rate, in (V.cm(-1)).V-1, turns out to be numerically equivalent to the characteristic length of the double layer, whatever the underlying model. Our calculated rates, carried out within the Gouy-Chapmann approximation, are in acceptable agreement with previous experimental estimates. First insights into our electropolymerization reactions suggest that the presumed intermediate chemisorbed radical-anions may have a borderline stability, i.e. a largely non negligible lifetime on the surface.

Nyckelord

DENSITY-FUNCTIONAL THEORY; CARBON-MONOXIDE; PLATINUM-ELECTRODE; METAL-SURFACES; INFRARED-SPECTRUM; BASIS-SETS; SPECTROSCOPY; ADSORPTION; APPROXIMATION; ACRYLONITRILE

TECHNOLOGY

TEKNIKVETENSKAP

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