M. Ocampo, P. Matter, C. Holt, A. Beutel, N. Casillas, H. Xu, S. Zhong, G. Bender, C. Quesada
pH Matter LLC,
Keywords: catalyst, heavy duty, fuel cells
Summary:Proton Exchange Membrane (PEM) fuel cells offer a clean and efficient means of energy conversion for numerous applications, including automotive power. Most automotive manufacturers are pursuing development of PEM fuel cell powered vehicles including heavy-duty trucks. Truck emissions account for 25% of CO2 emissions from the transportation sector and truck use is projected to grow. Unfortunately, wide-scale PEM fuel cell adoption is partially limited by the high cost of the fuel cell stacks, and the need to replace them in heavy-duty applications. The main issues are the high cost of the Platinum Group Metal (PGM) electrode materials and the relatively fast degradation of the electrodes (namely the cathode in both cases). To lower PEM fuel cell cathode costs, enhancement of the Pt catalyst activity is needed to reduce its loading levels. Further, because of the higher mileage and power demand of trucks, the cathode must be more durable than in conventional PEM fuel cells. One way of improving catalyst performance and durability is by optimizing the interaction between the catalyst and the support material. In this paper, we report a multi-functional carbon support, based on doped carbon nano-structures (i.e. CNxPy), that is engineered to perform better than conventional PEMFC pure carbon supports. Nitrogen and phosphorus doped carbon nano-fibers have been reported to enhance dispersion and provide better binding of Pt nano-particles when used as a support for PEM fuel cell catalysts and can also contribute to the ORR activity. In previous work, pH Matter developed catalysts based on a synthetic multi-functional catalyst supports (MFCS) that demonstrated DOE light-duty automotive targets for activity and durability at low-PGM loading. Further development is required to optimize catalysts and MEAs for more challenging heavy-duty applications. Because of the increasing interest for heavy-duty applications, recent work has focused on further optimization of the developed supports to stabilize Pt catalyst particles and allow for high performance to achieve heavy-duty durability and power performance targets. To enable higher platinum loading that is required for heavy-duty application, porosity of supports where optimized and a new graphitic support synthesized for improved corrosion resistance. Optimizations were also performed in our catalyst synthesis process to improve durability and power performance. From 25-cm2 MEA testing, excellent durability performance was achieved with the MFCS-based catalyst. This catalyst shows promising performance towards achieving DOE’s target of 1.07 A/cm2 at 0.7 V after heavy-duty accelerated stress testing. Continuous optimizations in catalyst synthesis and MEA fabrication is currently being performed to further enhance power performance at End-of-life (EOL). Progress towards meeting DOE’s heavy-duty million-mile target for performance and durability in MEAs will be presented.