Platinum group metal-free Fe-N-C catalysts for PEM fuel cells derived from nitrogen and sulfur doped synthetic polymers

Fe-N-C electrocatalysts were obtained via pyrolysis of N- or N/S co-doped synthetic polymers impregnated with FeCl3. The influence of the presence/absence of sulfur co-doping, the initial FeCl3 content and phenanthmline addition on the Fe-N-C-based cathode catalyst layers (CCLs) performance in H-2-air PEM fuel cells was studied. To this end the Fe-N-C materials were first characterized concerning their chemical composition, surface chemistry, porosity and morphology. Sulfur and phenanthmline additions strongly affect these characteristics of Fe-N-C materials. This in turn determines (to various extents) the electrochemical properties as measured with a rotating ring-disk electrode and upon infusion in the cathode catalyst layer in H-2-air PEM fuel cells. While simultaneous sulfur and phenanthroline addition yields Fe-N-C catalysts with high N-content and specific surface area, this does not translate into good electrochemical performance. We discuss the multitude of factors determining the catalysts' and the final CCLs' performances and conclude that the specific micro-colloidal morphology of the carbon gel-based materials dominates other Fe-N-C characteristics and determines overall FC performance. The best performing CCL provided peak power density of similar to 0.15 W.cm(-2) in a H-2-air PEMFC.

Automated summary

Fe-N-C electrocatalysts were prepared by pyrolysis of N- or N/S co-doped synthetic polymers with FeCl3, and the influence of sulfur and phenanthroline additives on their performance in fuel cells was studied. The results showed that the specific micro-colloidal morphology of the carbon gel-based materials dominated the catalysts' and the final CCLs' performances.