Preparation, characterization and degradation investigations of cathode catalysts for automotive PEM fuel cells systems
This research was designed to meet Daimler systematic efforts to address future electromobility demands. The work focuses on developing potential cathode catalysts and tests procedures to be employed in prototype fuel cells. In order to achieve commercial cost-competitive polymer electrolyte membrane fuel cells (PEM FC), the following major challenges have to be addressed: i) The catalytic mass activity of the cathode catalysts has to be at least 0.44 A/mg Pt representing an increased factor of four compared to standard carbon supported platinum Pt/C catalysts, ii) maintenance of an enhanced activity over the catalysts life time of about 6000 h, and iii) low cost of the cathode catalysts with less than 5 $/kW. To increase the performance and reduce the costs, Pt atoms of standard nanoparticle catalysts were partially replaced with non-noble metal Cu to result in PtCux-skeleton and core-shell. The durability of the catalysts prepared in-house was systematically evaluated and clarified for various fuel cell voltage cycles. A liquid electrolyte SU/SD test procedure is proposed and developed in this work, based on automotive stack voltage responses. The ex-situ test procedure has the advantage of being faster and less costly than in-situ tests. In addition, it allows distinguishing between quantifying the failure modes contributing to degradation: i) Pt dissolution, ii) Pt agglomeration and iii) carbon corrosion. Accelerated degradation test procedures for the Pt-based cathode catalysts, simulating the drive cycles, are also developed and discussed in this research. Square wave cycles (SWC) and triangular wave cycles (TWC) were systematically evaluated and compared. The knowledge achieved in this research provides technology insights to potential application in the electromobility development in Daimler.
Subject HeadingsPolymer-Elektrolytmembran-Brennstoffzelle [GND]
Fuel cells [LCSH]