Accelerated stress testing of PUREBLACK® carbon-based gas diffusion layers with pore forming agent for proton exchange membrane fuel cells

Abstract

Gas diffusion layer (GDL) configurations containing PUREBLACK® and VULCAN® carbons with 30 wt % polyethylene glycol as pore forming agent are evaluated under two ex-situ methods of accelerated stress testing (AST), in water and hydrogen peroxide (30%), for 1000 and 24 h, respectively. The samples are characterized via contact angle, scanning electron microscopy (SEM), porosity and pore size distribution and the fuel cell performance and durability are also evaluated, before and after the ASTs. Contact angle and SEM demonstrate extensive degradation impact on VULCAN® carbon, especially in hydrogen peroxide, with cracked surface due to carbon corrosion and wash-off, complete hydrophobicity loss, along with porosity increase. The fuel cell performance is evaluated at 60 and 100% RH at 70 °C, using O2 and air as oxidants, and the degraded VULCAN® carbon-based GDLs after the ASTs, result in significant performance loss and durability in air (~20% after 50 h) test shows non uniform gas distribution to the catalyst layer after ~30 h of continuous operation under constant current density 600 mA.cm−2, especially under high RH conditions. On the other hand, PUREBLACK®-based GDLs demonstrate superior durability in air (~12% after 50 h), possibly attributed to its graphitized carbon structure, as evident from the stable durability for 50 h.