Design of PGM-free cathodic catalyst layers for advanced PEM fuel cells.

The design of cathodic catalysts layer (CCL) consisted of Platinum Group Metal-free (PGM-free) electrocatalysts was done by catalyst coated membrane approach. Three different Fe-Mn-N-C compounds were synthesized with Fe:Mn ratio of 1:1, 2:1 and 2:1 with modified heat treatment profile. The catalysts were characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, pore and particle size distribution, zeta potential and transmission electron microscopy. Electrocatalysts were integrated into membrane electrode assembly and evaluated by electrochemical methods. Electrochemical impedance spectroscopy in combination with modeling were used for estimation of proton conductivity of CCL and its oxygen diffusivity. It was found that all CCLs possess extremely high proton conductivity, which was demonstrated for the first time for these types of PGM-free catalysts. The observed ORR mechanism was predominantly 4e- due to peroxide/radicals scavenging effect of Mn. [Display omitted] • Bi-metallic Fe-Mn-N-C PGM-free catalysts were synthesized. • Highly performed, industrial quality MEAs were fabricated. • Detailed electrochemical fuel cell evaluation was combined with EIS modeling. • The proton conductivity in catalyst layer was improved 5 times vs literature data. [ABSTRACT FROM AUTHOR]