Cathode Design of Non PGM Catalysts for Anion Exchange Membrane Fuel Cells

An anion exchange membrane fuel cell (AEMFC) using hydrazine hydrate liquid fuel has been developed¹ and the concept vehicle powered by Precious Metal free Liquid Feed Fuel Cell (PMfLFC) was exhibited at the 42^nd and 43rd Tokyo Motor Show. For the improvement of the AEMFCs, technological breakthrough is necessary for anion exchange membranes. Especially, it is important to overcome the counteracting relationship of high ion conductance and low fuel permeability. And also, technology to control triple-phase interface formed by catalyst and ionomer is important to improve the performance. Our approach to develop the advanced AEMFC is using anion conductive quaternized aromatic multiblock copolymers, poly(arylene ether)s (QPEs)² and control the interface and non platinum group metal (PGM) catalysts both for anode and cathode. Even for state-of-the-art proton exchange membrane fuel cell electrode that consists of Pt catalysts and perfluorinated ionomer, triple-phase interface has not been optimized and the catalyst utilization is still insufficient. This is also the case for non PGM catalyst and anion exchange ionomer. In this paper, for the preliminary study we focus on electrode design for cathode and evaluated pore size of non PGM catalyst and distribution of catalyst in the ionomer solution. The non PGM catalysts formed meso pores (10-100nm) with the mixture of carbon materials. There are two different types of pores, one is inside of the catalyst itself and the other one is outside pores between the catalysts. Mixture of non PGM catalyst and carbon materials  are increased meso pores. Oxygen reduction reaction (ORR) activity of the non-PGM catalysts was evaluated in 1M KOH aq using rotating ring disk electrode (RRDE). The Fe-N-C non-PGM catalyst showed comparable ORR performance to platinum/carbon catalyst (TEV10V60E). The half wave potentials were 0.886V and 0.849V, respectively. MEA consists of the QPE membranes and ionomers were fabricated with non-PGM catalysts and subjected to performance evaluation. The MEA performance of direct hydrazine fuel cells will be shown and discussed in the meeting.

References

[1] K. Asazawa, H. Tanaka, U. Martinez, B. Halevi, A. Serov, K. Artyushkova, P. Atanassov, and B. Kiefer, Abstract #1610, Honolulu PRiME 2012

[2] M. Tanaka, K. Fukasawa, E. Nishino, S. Yamaguchi, K. Yamada, H. Tanaka, B. Bae, K. Miyatake, and M. Watanabe, J. Am. Chem. Soc. 2011, 133, 10646–10654