Structure and Performance of Fe-N-C PGM-Free Cathode Catalysts Derived By Polymerization-Pyrolysis and Sacrificial Support Method

Tuesday, 3 October 2017: 14:20
National Harbor 14 (Gaylord National Resort and Convention Center)
Y. Chen, R. R. Gokhale, A. Serov (University of New Mexico), K. Artyushkova (Center for Micro-Engineered Materials), and P. Atanassov (University of New Mexico)
Recently numerous metal-nitrogen-carbon type cathode electrocatalysts for fuel cell have been synthesized via different approaches [1]. Among these methods, sacrificial support method (SSM) has been developed at UNM group to prepare iron-nitrogen-carbon (Fe-N-C) platinum group metal free (PGM-free) catalysts for oxygen reduction reaction (ORR) [2-6]. Based on this method, we adopted polymerization pyrolysis (PP) to synthesize novel porous Fe-N-C ORR catalysts.

Pyrolyzing polymers has been widely investigated with different nitrogen contained candidate selection, such as polypyridine [7] and polyaniline [8]. However, it is the first time to synthesize ORR catalyst via pyrolyzing C-N-C backbone pyridine based polymers. By introducing ammonia persulfate into water with well dispersed 2-amino-6-methylpyridine (26AMP) or 2,6-diaminopyridine (26DAP) and silica, well nitrogen-carbon bonded polymers could be prepared. FTIR spectra show that there is no amino group absorption, indicating a thorough three dimensional polymerization. The followed pyrolysis with iron salt, HF washing and second ammonia processing lead to a final nanoporous composite.

These different PP catalysts all have good electrochemical performance. 26AMP based materials have high half-wave potentials in both base and acidic environment, no matter silica is used in polymerization (in situ) or just mixed with polymer before pyrolysis (ex situ). All four 26AMP and 26DAP based materials have competitive peroxide yield, achieving the 2% target of Department of Energy [https://energy.gov/eere/fuelcells/durability-working-group].