Theoretical aspects of laminar flow in a channel-type electrochemical cell as applied to in situ attenuated total reflection-infrared spectroscopy

Analytic expressions are derived, within the Lévêque approximation, for the steady-state concentration profile of a reactant or a stable product generated via first-order kinetics at an electrode in a channel-type electrochemical cell under fully developed laminar flow. It is shown that for cell geometries and other experimental conditions easily realizable in the laboratory, the concentration of species directly above the insulating flat surface adjacent to the downstream edge of the electrode c(x,y), where x is the direction of fluid flow and y is the distance normal to the electrode surface, differs only slightly (less than 5%) from c(x,0), the concentration on the surface at the prescribed x, for values of y on the order of microns. Implications of these results to the quantitative analysis of in situ attenuated total reflection-infrared spectroscopy in a channel-type spectroelectrochemical cell (Barbour et al.⁶) are discussed.