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Online monitoring of electrocatalytic reactions of alcohols at platinum and gold electrodes in acidic, neutral and alkaline media by capillary electrophoresis with contactless conductivity detection (EC‐CE‐C 4 D)
Author(s) -
Ferreira Santos Mauro Sérgio,
Silva Lopes Fernando,
Gutz Ivano Gebhardt Rolf
Publication year - 2017
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201700124
Subject(s) - chemistry , platinum , electrode , capillary electrophoresis , electrochemistry , electrolysis , inorganic chemistry , detection limit , carboxylate , analytical chemistry (journal) , chromatography , organic chemistry , electrolyte , catalysis
An EC‐CE‐C 4 D flow system was applied to the investigation of electrocatalytic processes by monitoring carboxylic acids formed during the electro‐oxidation at various potentials of primary alcohols (mixture of 1 mmol/L of ethanol, n‐propanol, n‐butanol and n‐pentanol) in acidic, neutral and alkaline media. The electro‐oxidation was carried out on gold and platinum disk electrodes (3 mm of diameter) in a thin‐layer electrochemical flow cell. Products were sampled 50 μm apart from the electrode directly into the capillary. All the generated carboxylates were determined in near real time (less than 2 min) by CE‐C 4 D in counter‐flow mode, with Tris/HCl buffer solution (pH 8.6) as BGE. Long sequences of 5‐min experiments were run automatically, exploring the applied potential, electrolysis time and solution composition. Electro‐oxidation at 1.5 V (versus Ag/AgCl quasi‐reference) during 50 s in acidic medium was found appropriate for both Pt and Au electrodes when the determination of alcohols after derivatization is intended. A noteworthy selectivity effect was observed on the Au electrode. The signal corresponding to pentanoate is similar on both electrodes while the signal of ethanoate (acetate) is four times larger on gold than on platinum. The carboxylate signals were lower in alkaline medium (below the determination limit on Pt) than in acidic and neutral media. On gold, the formation of carboxylates was anticipated (0.85 V in alkaline medium versus 1.40 V in neutral medium). The automatic online monitoring of electrochemical processes by EC‐CE‐C 4 D holds great potential to investigate ionic/ionizable intermediates/products of new electrocatalysts and/or alternative fuels.