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Design and characterisation of metallic bipolar plates for proton exchange membrane fuel cells
Oladoye, Atinuke Modesola
Metals are potential candidate materials for proton exchange membrane fuel cells (PEMFC) bipolar plates (BP). However, metals require surface coatings to enhance its corrosion resistance and interfacial contact resistance (ICR) in PEMFC environments. The present study investigated the performance of metals coated with: graphite based coatings deposited by the CoBlast™ process and chromised coatings deposited by pack cementation in PEMFC environments. CoBlast™ coated metals exhibited high ICR and low corrosion resistance in 0.5 M H2SO4 + 2 ppm HF. Hence, it was unsuitable for PEMFC BP application. Post chromising of CoBlast™ coated stainless steel at 900oC for 3 hours reduced its ICR by ~72 % at 140 N/cm2 but increased its susceptibility to corrosion. Therefore, Box–Behnken design was employed to optimise and investigate the influence of activator content, time and temperature on the corrosion current density of chromised 304 stainless steels exposed to aerated 0.5 M H2SO4 + 2 ppm HF at 70 oC. Temperature was found to be the most significant parameter, while the optimum process conditions were: activator content of 6.84 wt. %, time of 3 hours and temperature of 1040 oC. The optimised coatings exhibited acceptable corrosion resistance in PEMFC environments and about six fold decrease in the ICR of the substrate at 150 N/cm2. However, pack carburisation at 925 oC for 3 hours prior to chromising decreased its ICR by 55% at 150 N/cm2Consequently, the single fuel cell with the modified chromised stainless steel BP attained a peak power density of 18.20 mW/cm2 at a current density of 53.2 mA/cm2. This result represented a two-fold and three-fold increase in the peak power density of the single fuel cells with chromised stainless steel produced at the optimised process conditions and uncoated BP respectively. A similar trend was sustained in the ten-hour durability test. Surface characterisation of the plates after the test indicated the need to adopt low temperature carburisation techniques. The work presented herein demonstrated that both chromising and pre-carburisation prior to chromising are promising techniques for surface modification of metallic PEMFC bipolar plates.
Keyword(s): Environmental engineering
Publication Date:
2016
Type: Other
Peer-Reviewed: Unknown
Language(s): English
Institution: Dublin City University
File Format(s): application/pdf
Related Link(s): http://doras.dcu.ie/21348/
First Indexed: 2017-11-30 06:56:20 Last Updated: 2018-09-02 06:05:21