Stoichiometry and carbon dioxide yields from ethanol and methanol oxidation in electrolysis and fuel cells

Majidi, Pasha (2017) Stoichiometry and carbon dioxide yields from ethanol and methanol oxidation in electrolysis and fuel cells. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

With the heavy demand for sustainable fuel sources instead of fossil fuels, fuel cells employing alcohols are becoming more attractive. The high theoretical efficiency (97%) of direct ethanol fuel cells (DEFCs) based on proton exchange membrane (PEM) technology together with the high energy density and availability of bioethanol make DEFCs important as power sources. However, the low faradic efficiency of DEFCs, the poisoning of the anode by adsorbed carbon monoxide (COads) during ethanol oxidation and crossover of fuel from the anode to the cathode are major issues in DEFCs technology. The main purpose of this research was to improve the faradic efficiency of DEFCs. Therefore, different potential waveforms were applied to an ethanol electrolysis cell with aqueous ethanol supplied to the anode and nitrogen at the cathode, in order to increase the yield of carbon dioxide and therefore increase cell efficiency relative to operation at a fixed potential. Also, we have developed a novel electrochemical method to measure the average number of electrons generated during oxidation of ethanol to carbon dioxide. The method is based on quantitative oxidation of fuel that crosses through the membrane to avoid the errors that would otherwise result from crossover. It is useful for rapid screening of catalysts, and allows performances (polarization curves) and n-values to be determined simultaneously under well controlled transport conditions. This method was also used for determination of n values for a cell in anode polarization mode and a real fuel cell.

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