Hydrodynamic studies of the electrochemical oxidation of organic fuels

Sayadi, Azam (2020) Hydrodynamic studies of the electrochemical oxidation of organic fuels. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

A clear understanding of small organic molecules (SOM) electrochemical oxidation opens a great opportunity for breakthrough in the development of fuel cell technology. SOM such as formic acid, methanol, and ethanol can produce electrical power through their oxidation in the fuel cell's anode. These molecules are also known as organic fuels and theoretically have the potential to produce close to 100% energy efficiency in a fuel cell. However, fast and complete oxidation of some organic fuels, such as ethanol, has not been achieved at this time, and has led to a dramatic decrease in the level of fuel cell efficiency. Therefore, a comprehensive study of the electrocatalytic oxidation mechanisms of organic fuels as well as a determination of the average number of transferred electrons (nₐᵥ) are crucial for the enhancement of fuel cell efficiency. Hydrodynamic methods are highly effective approaches for these study purposes, and they have the ability to emulate the hydrodynamic conditions of a fuel cell anode. The main purpose of this project was establishing a simple and novel system for the assessment of various fuel cell catalysts performances in relation to formic acid, methanol and ethanol electrochemical oxidation. For this purpose, we applied two different approaches of hydrodynamic techniques, rotating disk voltammetry (RDV) and ow cell electrolysis. Also, as for fuel cells, thick catalyst layers were applied in our studies in order to obtain meaningful data which are more relevant to an actual fuel cell. We showed that RDV is a convenient and useful method for the determination of the pure kinetic component of the oxidation current which represents a catalyst activity. Also, we estimated nav for methanol and ethanol using mathematical treatments related to RDV. Two-electrode and three-electrode ow-through cells were designed to determine the mass transport and kinetic parameters of the formic acid oxidation current, which can be further extended to methanol and ethanol for nₐᵥ determination. The two-electrode ow-through cell provided for rapid collection of oxidation products and real time measurements of CO₂ for stoichiometric investigations.

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