Synthesis, Pore and PTFE Distribution Studies of Monolithic Gas Diffusion Media for PEMFC By Varying Solvent

Abstract

Proton Exchange Membrane Fuel cells (PEMFC) are the focus of research internationally, due to their potential in solving energy problems by enabling energy conversion in a clean manner. Gas Diffusion Medium (GDM) is a vital component of a PEMFC which controls the transport of gas and water molecules. The performance of a fuel cell is impacted by mass transport losses. Existing GDMs are based on carbon paper and carbon cloth structures that are commercially available and have specific structures. These commercially available starting materials therefore restrict the overall design of the GDM to work within the constraints of their structure. In the present work the focus is to make a combined porous self standing GDM constituting meso and macro pores using Carbon black (CB) and PTFE. PTFE content as well as its distribution play a prominent role in wicking out water from the reaction site. Method for preparation of the self standing GDM is tailored with starting materials such as CB, Graphite, and Teflon. Factors affecting the uniform distribution of PTFE are identified. Pore size, uniformity and pore distribution obtained through the use of four different solvents – IsoPropylAlcohol (IPA), Glycerol, Ethanol, and Water, are studied. The GDMs prepared are characterized using SEM and Mercury Intrusion Porosimetry. Pore distribution, sizes and composition are examined using SEM images and composition maps on a comparative basis. Optimization of conductivity, hydrophobicity and water transport is carried out. The results obtained are presented and discussed and compared. The advantages a particular solvent and factor contributing an uniform PTFE distribution is recognized as a part of this approach.