Effect of Cathode Pore Volume on PEM Fuel Cell Cold Start

Abstract

Start-up of a proton exchange membrane (PEM) fuel cell from subzero temperatures, commonly referred to as cold start, remains a major challenge for automotive applications. In this work, we theoretically and experimentally study the effect of catalyst layer (CL) pore volume (or, more directly, CL thickness) on the cold-start performance of a PEM fuel cell for both isothermal and nonisothermal operations. Special attention is directed to determining the limits of a cold-start performance with an ultrathin CL . The cold-start product water or the operational time approaches a minimum nonzero asymptote as the CL is gradually made infinitesimally thin. For a PEM fuel cell with standard cell thermal mass, e.g., , and with moderately low initial membrane water content , successful start-up from at can be achieved for CL thicknesses of and above, whereas a CL thickness of is required for successful self-start-up from . However, successful start-up can be achieved even with a thick CL, given certain adjustments to cell design and material properties. In particular, we study the effects of cell thermal mass and membrane water diffusivity and present a design map for self-start-up of a CL PEM fuel cell from various subfreezing temperatures.