Direct Electro‐oxidation of Dimethoxymethane, Trimethoxymethane, and Trioxane and Their Application in Fuel Cells

Abstract

Significant advantages in weight, volume, and overall system performance of fuel cells would result if high‐energy organic substances such as methane and its derivatives can be made to undergo direct electro‐oxidation at the electrodes of the fuel cell without having to be converted by some catalytic process to hydrogen. This study demonstrates three novel fuels for direct‐oxidation‐type fuel cells. These new fuels are dimethoxymethane (DMM, dimethyl orthoformate), trimethoxymethane (TMM, trimethyl orthoformate), and trioxane (1,3,5‐trioxane). The electro‐oxidation and electrosorption characteristics of these new fuels at Pt, Pt‐Sn, and Pt‐Ru electrodes and the performance of these fuels in direct‐oxidation fuel cells is described. Sustained direct electrochemical oxidation of aqueous solutions of DMM, TMM, and trioxane at high current densities has been demonstrated for the first time in half‐cells and liquid‐feed polymer electrolyte fuel cells. The oxidation of these fuels leads to the formation of methanol and ultimately carbon dioxide. Cyclic voltammetry and steady‐state studies suggest that the electro‐oxidation processes occur by chemisorption steps followed by surface reactions of adsorbed intermediates. The electro‐oxidation of trioxane is preceded by an acid‐catalyzed hydrolysis step on Nafion and in sulfuric acid solutions. These new fuels are best used without further processing in direct liquid‐feed polymer electrolyte fuel cells.