Effects of toluene and benzoic acid on the kinetics of ferrous oxidation on Pt and nafion-coated Pt electrodes

Journal Article · Wed Jun 01 04:00:00 EDT 1994 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2054950· OSTI ID:7149946

Ye, J H; Fedkiw, P S ^[1]

---

1. North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemical Engineering

The electrochemical kinetics of Fe[sup 2+] oxidation to Fe[sup 3+] have been investigated by cyclic and ring disk electrode voltammetry in the absence and presence of the contaminants toluene (7 mM, saturated solution) or benzoic acid (16 mM) in 1M H[sub 2]SO[sub 4] electrolyte on (1) smooth Pt electrodes, (2) Nafion-coated smooth Pt electrodes, and (3) Pt electrodes electrodeposited within a Nafion film coated onto a glassy carbon (GC) substrate. On uncoated Pt, the kinetics are adversely affected by these two organics: both the anodic transfer coefficient and the apparent standard rate constant are decreased. A 3.7 [mu]m Nafion coating, however, effectively buffers the smooth Pt electrode from toluene, but, nevertheless, benzoic acid still affects the reaction rate. In contrast, the transfer coefficient and rate constant for Fe[sup 2+] oxidation on the Pt/Nafion/GC electrode are essentially unaffected by either toluene or benzoic acid. Qualitative features of the voltammograms also indicate that the Nafion film protects the Pt from contamination by these aromatics: two current plateaus are observed using an uncoated Pt electrode in the presence of toluene or benzoic acid with a ratio which increased with rotation rate; with the Nafion coating on a smooth Pt electrode and in the presence of toluene, however, there is only one current plateau; in the presence of benzoic acid, two current plateaus remain, but the ratio is nearer unity and less sensitive to rotation rate. In contrast, only a single plateau current is observed using the Pt/Nafion/GC electrode. The Nafion coating is apparently an effective buffer layer against these two aromatics, but concurrently affects a decrease in the mass-transfer limited current due to the diffusional resistance of the film.

• OSTI ID: 7149946
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 141:6; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
ALKYLATED AROMATICS
AROMATICS
BENZOIC ACID
CARBOXYLIC ACIDS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
ELECTROCHEMISTRY
ELEMENTS
HYDROCARBONS
IRON
KINETICS
METALS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDATION
PLATINUM
PLATINUM METALS
REACTION KINETICS
TOLUENE
TRANSITION ELEMENTS
VOLTAMETRY