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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]

Proton Exchange Membrane (PEM) fuel cell electrodes with different ionomer contents were studied with various microscopic techniques. The morphology and surface potential were examined by Atomic Force Microscopy (AFM) and Kelvin Probe Microscopy (KPM), respectively. The particulate nature of the electrode was well displayed in the topography and phase images. The particle and pore size (Z) distributions showed the most frequent values at 30–40 nm and 20–30 nm, respectively. The particle size corresponds to the size of the carbon support for the platinum catalyst. Catalyst agglomeration was observed in high ionomer content electrodes. The surface potential images showed distinct difference to the topography images. The overall grain size was seen to increase, the pore volume to decrease, the surface roughness to decrease, and the surface potential variation to increase with the increase of ionomer content in the catalyst layer. Transmission electron microscopy (TEM) was carried out on selective electrodes to provide additional information and confirmed with the AFM results. Cyclic voltammetry (CV) showed that the electrode containing 30 wt.% ionomer has maximum catalyst utilization. [ABSTRACT FROM AUTHOR]

A new platinum group metal (PGM)-free proton exchange membrane fuel cell (PEMFC) cathode catalyst materials, synthesized using the VariPore™ method by Pajarito Powder, LLC, are characterized for their structure and activity. The physico-chemical analysis of the iron-nitrogen-carbon (Fe-N-C) electrocatalysts show mesoporous carbon material effectively doped with iron and nitrogen. The materials have an average pore size of 7–8 nm and high specific surface area. The Fe-N-C catalysts exhibit good oxygen reduction reaction (ORR) activity in 0.5 M H 2 SO 4 electrolyte with high half-wave potential and sustainable electrochemical stability over 10,000 repeated potential cycles with insignificant losses in their activities. As cathode catalysts in a PEMFC, the Fe-N-C materials deliver remarkably good fuel cell performance at low overpotential approaching that of the commercial Pt catalyst. The high ORR electrocatalytic activity of these Fe-N-C catalysts is credited to the synergy between nitrogen-moieties, specifically pyrrolic-N, pyridinic-N, and graphitic-N, and iron in addition to the high mesoporosity that facilitate an effective reaction path in boosting the electrocatalytic activity and stability. [Display omitted] • State-of-the-art commercial PGM-free catalysts for ORR were characterized and evaluated. • Was shown that active centres are atomically dispersed. • Performance of electrocatalysts was evaluated in industrially manufactured MEA form-factor. • The fuel cell performance is close to the state-of-the-art R&D PGM-free catalysts. [ABSTRACT FROM AUTHOR]

To elucidate the evolution of ionomer-Pt and ionomer-carbon interfaces during life cycle of polymer electrolyte fuel cells (PEFCs), electrodes with high surface area (HSA) and durable carbon supports underwent catalyst and carbon corrosion accelerated stress tests (ASTs) under stoichiometric and sub-stoichiometric gas flow conditions. Electrochemical characterizations, as well as X-ray photoelectron spectroscopy (XPS) were utilized to assess degree of components degradation. Catalyst AST results revealed that Pt nanoparticles dispersed within the micro- and meso-pores and not in contact with ionomer are the main contributor to the 50% electrochemical surface area (ECSA) loss observed after 30k cycles resulting in significant polarization loss, which is much more notable in the case of sub-stoichiometric operating condition. Support AST results for HSA carbon showed severe ionomer degradation and 55% ECSA loss within the first 100 cycles, while cell with durable support exhibited negligible polarization and ECSA decay during the first 2500 cycles attributed to higher ionomer coverage, preservation of proton pathways preventing Pt from detachment. [Display omitted] • Interfaces evolution are evaluated during accelerated stress tests (ASTs) for fuel cells. • Pt that is not in contact with ionomer degrades the most for catalyst AST. • Ionomer degradation is observed for all ASTs. • Graphitized carbon supports mitigate corrosion and Pt loss. [ABSTRACT FROM AUTHOR]