NMR studies of mass transport in high-acid-content fuel cell membranes based on phosphoric acid and polybenzimidazole

被引:66
作者
Jayakody, J. R. P. [1 ]
Chung, S. H.
Durantino, L.
Zhang, H.
Xiao, L.
Benicewicz, B. C.
Greenbaum, S. G.
机构
[1] CUNY Hunter Coll, Dept Phys, New York, NY 10021 USA
[2] William Paterson Univ New Jersey, Dept Chem & Phys, Wayne, NJ 07470 USA
[3] Rensselaer Polytech Inst, New York State Ctr Polymer Synth, Dept Chem & Chem Biol, Troy, NY 12180 USA
关键词
D O I
10.1149/1.2405726
中图分类号
O646 [电化学、电解、磁化学];
学科分类号
081704 ;
摘要
Mass-transport studies of phosphoric acid (PA)-doped meta-polybenzimidazole (PBI) fuel cell membranes are described. In this study, the fundamental differences in transport properties between m-PBI/ PA membranes prepared by conventional imbibing procedures and the polyphosphoric acid (PPA) process are explored. The membranes were characterized by proton conductivity and multinuclear (H-1 and P-31) magnetic resonance measurements. Both short-range and long-range dynamical processes were investigated by spin-lattice and spin-spin relaxation time measurements and by pulsed field gradient diffusion, respectively. Comparative data for pure PA and PPA are included. The high proton conductivity (0.13 S/cm at 160 degrees C) of the PPA-processed membranes is correlated with rapid proton self-diffusion (3 x 10(- 6) cm(2)/s at 180 degrees C). The P-31 results reveal the presence of both PA and the dimeric pyrophosphoric acid and indicate strong interaction between the phosphate groups and the m-PBI matrix, with negligible anionic transport for both kinds of membranes. The higher concentration of PA in the PPA-processed membranes and differences in membrane morphology may provide an additional proton-transport mechanism involving rapid exchange between the PA and pyrophosphoric acid species. (c) 2006 The Electrochemical Society. All rights reserved.
引用
收藏
页码:B242 / B246
页数:5
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