Galvano- and Potentio-dynamic studies during ethanol electro-oxidation reaction in acid vs. alkaline media: Energy dissipation and blocking nature of potassium

Autor(es)

Sallum, Loriz F. ^[1] ; Mota-Lima, Andressa ^[1] ; Gonzalez, Ernesto R. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Chem Sao Carlos, POB 780, BR-13560970 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Electrochimica Acta; v. 293, p. 247-259, JAN 10 2019.
• Citações Web of Science: 2

Resumo

Despite the net energy yield be the primary goal of ethanol electro-oxidation reaction (EOR), it is never measured in fundamental electrochemical studies. By combining galvanodynamic and potentiodynamic profiles of the steady states of the system, we demonstrate a methodology to estimate the dissipation of chemical energy that allows the inference of the fuel cell power output in relative terms. Apart from the empirical energy dissipation, several kinetic information are unravelled: (a) the kinetics is governed by ethanol adsorption rate for both media and for both external control modes; and (b) either the maximum current sustained by EOR or the steady state currents are, in addition, governed by a global coverage of poisonings species, which includes the contributions from COad and non-reactive OHad. The blocking effect of potassium cations over EOR is clearly verified, reducing the maximum activity up to a factor of 0.19, which is interpreted as an effect of the high coverage of non-reactive OHad. Finally, it is expected a slightly improvement of the power output of a direct ethanol fuel cell operating at steady state in alkaline media due to the lower chemical dissipation at fixed interfacial current value. Nonetheless, the blocking effect of potassium in alkaline media may, depending on the concentration, either induces an oscillatory regime at higher overvoltage (above 0.57 V) along with the preservation of the energy generation at lower overvoltage or completely decrease the energy generation due to a drastic loss of energy used to polarize the EOR. (c) 2018 Published by Elsevier Ltd. (AU)

• Processo FAPESP: 15/20443-0 - Cinética oscilatória e eletrocatálise da eletrooxidação de moléculas orgânicas pequenas em superfície monocristalinas
• Beneficiário: Loriz Francisco Sallum
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 13/24162-0 - Eletro-oxidação de moléculas orgânicas pequenas em meio alcalino: cinética complexa e eletrocatálise
• Beneficiário: Loriz Francisco Sallum
• Modalidade de apoio: Bolsas no Brasil - Doutorado