Atomistic Modeling of Key Factors in Catalytic Ethanol Oxidation

Mei, Yuhan

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Atomistic Modeling of Key Factors in Catalytic Ethanol Oxidation

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Direct ethanol fuel cells (DEFCs) is a promising technology for generating electricity via the direct conversion of ethanol into CO2. The key to the process is the ethanol oxidation reaction (EOR), which occurs over a catalyst at the fuel cell anode and produces CO2 and 12 e– per ethanol molecule during complete oxidation. However, the implementation of DEFCs is hindered by incomplete oxidation, leading to low CO2 selectivity and fewer electrons than 12 e– being produced. Breaking the C-C/C-H bonds of ethanol is essential for complete oxidation. The state of the metal, the presence of solvent, and electrical fields may all strongly influence the EOR. However, simulation efforts often ignore these phenomena, and consider pristine model surfaces. Methods to better describe electrochemical environments are still being developed and are an ongoing area of research. Herein, we modeled the ethanol oxidation reactions (EOR) using density functional theory. We assessed how presence of solvents, electrical fields, and oxidation of the metal catalyst may influence important C-C and C-H bond scission reactions. Our results indicated that the presence of water and ethanol solvation can not only facilitate bond scission, but may also change the preferred mechanism pathway. The addition of negative electric potential can also substantially enhance C-C/C-H bond scission of ethanol molecules. Metal oxidation can significantly lower the reactions energies and promote C-C/C-H bond scission. Overall, the current work provides guidelines on how to better model EOR, and provides insight for experimentalists developing new EOR catalysts.

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