Investigation of pinhole defects in gas diffusion layers for the quality control of proton exchange membrane fuel cells

Abstract

The gas diffusion layer (GDL), one of the essential components of the membrane electrode assembly (MEA), plays an important role in the performance of proton exchange membrane fuel cells. With respect to this essential component and its specifications, this work intends to examine the impact of GDL defects and their effects on cell performance for component quality control. To understand how GDL defect affects its performance and to what level the defect takes effect, ex situ characterization and in situ fuel cell testing are conducted by comparing pristine and defective GDLs. While ex situ GDL properties incorporate measurements of thickness, conductivity, and permeability under compression, in situ investigation mainly involves polarization curve and electrochemical impedance spectroscopy. Among different types of GDL defects, pinholes are targeted in this work. As such, the evaluation focuses on assessing the effects of varying numbers and sizes of pinhole defects under different relative humidities (RHs). Using the state-of-the-art GDLs, an improved cell performance is observed with defective GDLs (evenly distributed 40 pinholes with a diameter of 0.58 mm) under 100% RH. Results also show that the effect of pinhole defects is sensitive to RH, as well as operating current densities.