Ionomer Layer Design of the Electrode Using PGM-Free Electrocatalysts for Anion Exchange Membrane Fuel Cells

An anion exchange membrane fuel cell (AEMFC) using hydrazine hydrate liquid fuel has been investigated1 and the concept vehicle was exhibited at the 42nd and 43rdTokyo 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. In addition, technology to optimize triple-phase interface formed by catalyst and ionomer is important to improve the performance. Through many efforts to control the triple-phase interface, state-of-the-art proton exchange membrane fuel cell electrode that consists of platinum group electrocatalysts and perfluorinated ionomer has been investigated. However, the catalyst utilization is still insufficient. In addition, it is more challenging to control the triple phase interface for PGM-free electrocatalysts and anion exchange ionomers. Our approach to develop the advanced AEMFC is using anion conductive quaternized aromatic multiblock copolymers, poly(arylene ether)s (QPEs)2as shown in Fig.1 and controling the interface and PGM-free electrocatalysts both for anode and cathode. In this preliminary study, we focus on ionomer layer design for anode and cathode evaluated by ionomer thickness covered on the electrocatalysts. (TEM image shown in Fig.2) MEA consisting of the QPE membranes and ionomers was fabricated with PGM-free electrocatalysts and subjected to performance evaluation. The MEA performance of direct hydrazine fuel cells will be shown and discussed in the meeting. Figure captions Fig. 1. Representative structure of QPEs.3 Fig. 2. TEM Image of ionomer layer (red line) on the cathode catalysts. References [1] K. Asazawa, K. Yamada, H. Tanaka, A. Oka, M. Taniguchi, and T. Kobayashi, Angew. Chem. Int. Ed., 46, 8024, 2007. [2] M. Tanaka, K. Fukasawa, E. Nishino, S. Yamaguchi, K. Yamada, H. Tanaka, B. Bae, K. Miyatake, and M. Watanabe, J. Am. Chem. Soc., 133, 10646–10654, 2011 [3] R. Akiyama, N. Yokota, E. Nishino, K. Asazawa, and K. Miyatake, submitted. Acknowledgements This work was supported by CREST, JST. Figure 1