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Lefevre M.,Canetique Electrocatalysis Inc. | Dodelet J.P.,INRS - Institute National de la Recherche Scientifique
ECS Transactions | Year: 2012

Polymer electrolyte membrane fuel cells (PEMFC) are electrical power generators for a wide range of possible applications, but are still considered too expensive for many. To reduce their cost, much research has focused on replacing the expensive Pt-based electrocatalysts in PEMFCs with a lower-cost alternative. Fe-based cathode catalysts are a promising alternative. To compete with Pt-based cathode catalysts, non-precious metal catalysts must meet three key criteria: have high catalytic activity, allow for high power density at meaningful cell voltages and have adequate operational stability/durability. Over the last three years our research group at INRS-EMT has made significant progress in achieving these criteria including a cathode catalyst with a power density of 0.75W cm-2 at 0.6V under H2/O2, a meaningful voltage for PEMFC operation, comparable with that of a commercial Pt-based cathode tested under identical conditions.

Kramm U.I.,TU Brandenburg | Lefevre M.,Canetique Electrocatalysis Inc. | Bogdanoff P.,Helmholtz Center Berlin | Schmeisser D.,TU Brandenburg | Dodelet J.-P.,INRS - Institute National de la Recherche Scientifique
Journal of Physical Chemistry Letters | Year: 2014

The applicability of analyzing by Mößbauer spectroscopy the structural changes of Fe-N-C catalysts that have been tested at the cathode of membrane electrode assemblies in proton exchange membrane (PEM) fuel cells is demonstrated. The Mößbauer characterization of powders of the same catalysts was recently described in our previous publication. A possible change of the iron species upon testing in fuel cell was investigated here by Mößbauer spectroscopy, energy-dispersive X-ray cross-sectional imaging, and neutron activation analysis. Our results show that the absorption probability of γ rays by the iron nuclei in Fe-N-C is strongly affected by the presence of Nafion and water content. A detailed investigation of the effect of an oxidizing treatment (1.2 V) of the non-noble cathode in PEM fuel cell indicates that the observed activity decay is mainly attributable to carbon oxidation causing a leaching of active iron sites hosted in the carbon matrix. (Graph Presented). © 2014 American Chemical Society.

Dodelet J.-P.,INRS - Institute National de la Recherche Scientifique | Chenitz R.,INRS - Institute National de la Recherche Scientifique | Yang L.,INRS - Institute National de la Recherche Scientifique | Lefevre M.,Canetique Electrocatalysis Inc.
ChemCatChem | Year: 2014

The possibility of a new iron-based catalytic site for the oxygen reduction reaction, comprising outer graphitic layers encasing a Fe3C core, is discussed in the context of iron-based catalysts for proton-exchange membrane fuel cells. Further analysis of new Fe3C-700 and S2-700 catalysts is still needed to determine the relationship between the active sites and oxygen reduction activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li Y.,University of Western Ontario | Li X.,University of Western Ontario | Geng D.,University of Western Ontario | Tang Y.,University of Western Ontario | And 4 more authors.
Carbon | Year: 2013

Carbon materials have been widely used as cathodes in lithium oxygen batteries but the detailed influence of the structure of these materials on their performance is not very clear yet. In this study, the same starting pristine commercial carbon black (N330) was treated under different atmospheres and the resultant carbons were employed as cathode materials for lithium oxygen batteries. It was demonstrated that the porosity and surface topology of these carbons tremendously changed as their treating time increased. The parameters that influenced the battery performance were identified. It was found that the main factor determining the battery performance is the specific surface area of the carbon mesopores, while nitrogen- or oxygen-bearing functionalities, introduced in these carbons during their heat-treatment or by contact with air after their pyrolysis, had little or no influence on the battery performance. © 2013 Elsevier Ltd. All rights reserved.

Szakacs C.E.,INRS - Institute National de la Recherche Scientifique | Lefevre M.,Canetique Electrocatalysis Inc. | Kramm U.I.,INRS - Institute National de la Recherche Scientifique | Kramm U.I.,TU Brandenburg | And 2 more authors.
Physical Chemistry Chemical Physics | Year: 2014

The oxygen reduction catalytic activity of carbon-supported FeN4 moieties bridging micropores between two graphene sheets was investigated by density functional theory (DFT). Based on the FeN2+2/C structure proposed earlier by our group, two types of FeN2+2/C structures were considered: one mostly planar and one in which the Fe ion is significantly displaced out of the graphitic plane. A structure in which the FeN4 moiety is embedded in an extended graphene sheet (FeNpyri4/C) was also considered. In addition, we have investigated the influence of an axial pyridine group approaching the Fe centre. The formation energy is lowest for the planar FeN2+2/C structure. The overall downhill behaviour of the relative free energy vs. the reaction step suggests that most structures have catalytic activity near zero potential. This conclusion is further supported by calculations of the binding energies of adsorbed O2 and H 2O and of the O-O bond lengths of adsorbed O2 and OOH. The side-on interaction of adsorbed O2 is preferred over the end-on interaction for the three basic structures without the axial pyridine. The pyridine coordination produces a stronger binding of O2 for the planar FeN2+2/C and the FeNpyri4/C structures as well as a dominant end-on interaction of O2. The energy levels of the planar FeN 2+2/C structure with and without the pyridine ligand are nearly equal for iron spin states S = 1 and S = 2, suggesting that both configurations are formed with similar concentration during the preparation process, as also previously found for two of the iron sites by Mössbauer spectroscopy experiments. This journal is © the Partner Organisations 2014.

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