(Digital Presentation) Fuel Cell Electrode Design - Using a Specially-Modified Force Tensiometer for Gas Bubble Adhesive Force Measurements on Nanostructured Copper Electrodes Submerged in a Liquid

Abstract

Direct liquid-feed fuel cells (DLFCs) have gained attention because of their low-cost, high power densities and clean energy. They have a bright future for both mobile andstationary applications. DLFCs directly convert chemical energy into electrical energy by the oxidization of liquid fuels. Numerous nanostructured catalysts on the electrodes have been explored to improve the energy conversion efficiency. However, the behavior of the gas products (such as N2 and CO2) on the electrode surfaces received very little attention, which is critical to achieve better performance of the DLFCs especially at high reaction rates. The reason for this is that gas bubbles that accumulate on the surface will not only block the catalyst sites but also cause high pressure in the liquid flow area limiting the fuel crossover. It has been reported that the surface architecture can significantly affect the gas bubble adhesion behavior.In this work, adhesive forces of the gas bubbles on planar and nanostructured films were measured. Using a force tensiometer outfitted with a video camera and software, adhesion force of the gas bubble on a flat Cu foil was measured. Adhesive forces and submerged liquid contact angle measurements of gas bubbles on planar and nanostructured Cu films are possible. Adhesive forces of liquids in air phase or of gas bubbles under liquid phase can also be analyzed. The special force tensiometer system with video upgrade combines a force measurement to determine the force of adhesion and an optical system to determine the area of contact between the liquid/gas and solid phase for each force that is measured. In such a way, force per area can be determined. The measurement procedure involves a liquid or gas bubble being pushed onto a solid substrate under air or liquid and then pulled off.