Design and Development of Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells at Various Relative Humidity Conditions

In the present study, primarily, gas diffusion layer samples containing microporous layers (MPLs), are fabricated using carbon paper substrate, PUREBLACK® carbon powder and polyethylene glycol (PEG) as pore forming agent. The GDLs are studied in single cell fuel cell, to evaluate the effect of porosity of the micro-porous layer on the performance at different operating relative humidity conditions and compared with commercial GDLs. Scanning electron microscopy (SEM) and contact angle measurements indicate crack-free surface morphology and hydrophobic characteristics of the PUREBLACK® based GDLs, respectively. By varying the wt. % of PEG, fuel cell performance is evaluated under relative humidity conditions of 60 and 100 % using H2/O2 and H2/Air at 70 oC and the durability is also evaluated for the samples without, with 30% PEG and commercial. The fuel cell performance of the GDL with 30 % PEG (with pore volume 1.72 cc.g-1) exhibited higher performance (444 and 432 mW.cm-2 at 60 and 100 % RH conditions, respectively using H2 and air) compared to that without pore forming agent (436 and 397 mW.cm-2).Subsequently, the best performing configuration underwent two different ex-situ methods of accelerated stress testing (AST), in water and hydrogen peroxide (30%), for 1000 and 24 h, respectively. The samples were evaluated via contact angle, SEM, and fuel cell performance, before and after the ASTs, and compared to similar configuration, using carbon powder VULCAN® (XC-72R), and aged in the exact same conditions. Contact angle and SEM demonstrated greater degradation of VULCAN® carbon, especially in hydrogen peroxide, where carbon corrosion caused surface cracks and change in hydrophobicity. The fuel cell performance and durability, evaluated at 60 and 100% RH at 70 oC, using O2 and air as oxidants, confirmed that VULCAN® carbon is more prone to carbon corrosion, with significant performance loss (12-19%) in contrast to PUREBLACK® that demonstrated higher carbon corrosion resistance due to its graphitized surface.