A study of ethylamine at a gold rotating ring‐disk electrode using pulsed electrochemical detection at the ring

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Abstract
Linear scan (cyclic) voltammetry at the disk with simultaneous pulsed electrochemical detection (PED) at the ring of a rotated ring‐disk electrode (RRDE) is demonstrated to be applicable for studies of the complex anodic behavior of ethylamine at gold electrodes in 0.10 M NaOH. The oxidation of ethylamine at the disk occurs during positive scans concomitantly with formation of surface oxide (Au → AuOH → AuO). However, the final oxide‐covered surface (AuO) is inert for further ethylamine oxidation. Data obtained at the RRDE demonstrate that the total ethylamine signal at the disk is composed of simultaneous contributions from: oxidative desorption of ethylamine preadsorbed at the oxide‐free Au surface and oxidation of ethylamine transported to the disk simultaneously with oxide formation. Based on ring‐disk data, preadsorbed ethylamine is estimated to correspond to a fractional surface coverage of 0.7 ± 0.1 monolayer for 10 to 60 μM ethylamine. Of this coverage, ca. 75% corresponds to ethylamine coadsorbed reversibly with OH− and 25% to ethylamine adsorbed irreversibly by a mechanism concluded to be chemisorption.