The sluggish oxygen reduction reaction (ORR) and the high platinum loading in the cathode are important obstacles that should be overcome for the development of H₂/air fuel cells. Thus, studies focused on highly active and cost-effective electrocatalysts have gained attention. Electrocatalysts formed by earth-abundant elements such as those based on iron, nitrogen and carbon (Fe-N-C) have gained considerable attention in research because they allow widespread commercialization of the fuel cells. Previous achievements regarding Fe-N-C oxygen reduction electrocatalysts have been described elsewhere and showed a significant effect of the carbon matrix surface area on the electrocatalytic activity and stability [1,2]. In the present paper, we will focus on the results of the consequence on activity and durability of the thermal treatments on Fe-N-C. The electrocatalyst were synthesized via Fe complexation with phenanthroline, followed by impregnation on carbon powder with different surface areas (Vulcan XC-72R and Black Pearls 2000). The thermal treatments were conducted at different temperatures and on Ar or NH₃ atmosphere. The discussion will be focused on the correlation between the results encountered in the characterization by EXAFS, XRD and HR-TEM with those obtained during polarization experiments for the ORR using rotating disk electrode and during fuel cell tests. A strong effect of the thermal treatment temperature and of the surface area of the carbon powder was observed on the activity and durability, mainly for the fuel cell tests with H₂/air. We believe that the results from this study may contribute to further understand the parameters that govern the activity and durability of Fe-N-C ORR catalysts.

[1] G.Wu, K.L. More, P. Xu, H-L. Wang, M. Ferrandon, A.J. Kropf, D.J. Myers, S. Ma, C.M. Johnston, P. Zelenay, Chem. Commun., 49 (2013) 3291 – 3293.

[2] L. Yang, N. Larouche, R. Chenitz, G. Zhang, M. Lefevre, J-P. Dodelet, Electrochim. Acta 159 (2015) 184 – 197.

Acknowledgements

The authors gratefully acknowledge financial support from FAPESP (2013/16930-7, and 2016/13323-0) and CNPq.