The electro-oxidation of ethylene glycol on platinum over a wide pH range: oscillations and temperature effects

PLoS One. 2013 Sep 18;8(9):e75086. doi: 10.1371/journal.pone.0075086. eCollection 2013.

Abstract

We report a comprehensive study of the electro-oxidation of ethylene glycol (EG) on platinum with emphasis on the effects exerted by the electrolyte pH, the EG concentration, and temperature, under both regular and oscillatory conditions. We extracted and discussed parameters such as voltammetric activity, reaction orders (with respect to [EG]), oscillation's amplitude, frequency and waveform, and the evolution of the mean electrode potential at six pH values from 0 to 14. In addition, we obtained the apparent activation energies under several different conditions. Overall, we observed that increasing the electrolyte pH results in a discontinuous transition in most properties studied under both voltammetric and oscillatory regimes. As a relevant result in this direction, we found that the increase in the reaction order with pH is mediated by a minimum (~ 0) at pH = 12. Furthermore, the solution pH strongly affects all features investigated, c.f. the considerable increase in the oscillatory frequency and the decrease in the, oscillatory, activation energy as the pH increase. We suggest that adsorbed CO is probably the main surface-blocking species at low pH, and its absence at high pH is likely to be the main reason behind the differences observed. The size of the parameter region investigated and the amount of comparable parameters and properties presented in this study, as well as the discussion that followed illustrate the strategy of combining investigations under conventional and oscillatory regimes of electrocatalytic systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Electrochemical Techniques
  • Ethylene Glycol / chemistry*
  • Hot Temperature*
  • Hydrogen-Ion Concentration
  • Oxidation-Reduction
  • Platinum / chemistry*

Substances

  • Platinum
  • Ethylene Glycol

Grants and funding

ES (Grant No. 160499/2011-9 and 200939/2012-2) and HV (Grant No. 306151/2010-3) thank Conselho Nacional de Desenvolvimento Científico e Tecnológico for financial support. HV (Grant No. 09/07629-6) and RN (Grant No. 09/00153-6) acknowledge FAPESP for financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.