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Journal of the Electrochemical Society, Vol.159, No.6, F166-F173, 2012
Electrochemical and Isotopic Investigation of C-13-Enriched Oxalic Acid Facilitated with a Vacuum Electrochemical Reactor
The electrolytic decomposition of C-13-enriched oxalic acid was investigated. Oxalic acid and oxalic acid-C-13(2) were pre-purified by vacuum sublimation and characterized by assay, melting range, and FTIR. An Integrated Vacuum Electrochemical Reactor (IVER) was employed to convert aqueous-phase oxalic acid to CO2 for the C-13-enrichment determinations: oxalic acid solvation, vacuum degas, electrolysis, and mass spectrometric analysis. Highly enriched oxalic acid-C-13(2) was electrolyzed at 1.5-VDC and the CO2 determined to be 99.5 atom%-C-13. Blends of H2C2O4 and (H2C2O4)-C-13 were prepared from 50.5 to 99.5 atom%-C-13, dissolved in water, and electrolyzed. For each blend solution, the [C-12/C-13] isotope separative effect was observed as increases in the (CO2) C-13-enrichment when the aqueous-phase was repeatedly electrolyzed. Furthermore, 50 atom%-C-13 oxalic acid was electrolyzed while the IVER current was monitored, and thereby the electrolytic isotope separation factor alpha[C-12/C-13] is estimated to be 1.03 +/- 0.01, at 295 K on platinum. Cyclic voltammograms of 0.10-mole% oxalic acid in water displayed an irreversible oxidation peak at E = +0.95 volt (oxalic acid) and another oxidation peak at E >=+1.6 volt (water). Cyclic voltammograms of oxalic acid in EMI+BETI- indicate that H2C2O4 can also be oxidized in liquid salts (voltammetric window similar to 1.4 volt versus Ag/AgCl). (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.089206jes] All rights reserved.