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Malek K.,NRC Institute for Fuel Cell Innovation | Malek K.,Simon Fraser University | Franco A.A.,CEA Grenoble
Journal of Physical Chemistry B | Year: 2011

This work is comprised of a versatile multiscale modeling of carbon corrosion processes in catalyst layers (CLs) of polymer electrolyte fuel cells (PEFCs). Slow rates of electrocatalytic processes in CLs and materials aging are the main sources of voltage loss in PEFCs under realistic operating conditions. We combined microstructure data obtained from coarse-grained molecular dynamics (CGMD) simulations with a detailed description of the nanoscale elementary kinetic processes and electrochemical double-layer effects at the catalyst/electrolyte and carbon/electrolyte interfaces. We exclusively focused on morphology and microstructure changes in the catalyst layer of PEFCs as a result of carbon corrosion. By employing extensive CGMD simulations, we analyzed the microstructure of CLs as a function of carbon loss and in view of ionomer and water morphology, water and ionomer coverage, and overall changes in carbon surface. These ingredients are integrated into a kinetic model, which allows capture of the impact of the structural changes on the PEFC performance decay. In principle, such multiscale simulation studies allow a relation of the aging of CLs to the selection of carbon particles (sizes and wettability), the catalyst loading, and the level of ionomer structural changes during the CL degradation process. © Published 2011 by the American Chemical Society.

Wang G.,University of South China | Wang G.,NRC Institute for Fuel Cell Innovation | Zhang L.,NRC Institute for Fuel Cell Innovation | Zhang J.,NRC Institute for Fuel Cell Innovation
Chemical Society Reviews | Year: 2012

In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references). © 2012 The Royal Society of Chemistry.

Chen H.M.,National Taiwan University | Chen C.K.,National Taiwan University | Liu R.-S.,National Taiwan University | Zhang L.,NRC Institute for Fuel Cell Innovation | And 2 more authors.
Chemical Society Reviews | Year: 2012

This review concerns the efficient conversion of sunlight into chemical fuels through the photoelectrochemical splitting of water, which has the potential to generate sustainable hydrogen fuel. In this review, we discuss various photoelectrode materials and relative design strategies with their associated fabrication for solar water splitting. Factors affecting photoelectrochemical performance of these materials and designs are also described. The most recent progress in the research and development of new materials as well as their corresponding photoelectrodes is also summarized in this review. Finally, the research strategies and future directions for water splitting are discussed with recommendations to facilitate the further exploration of new photoelectrode materials and their associated technologies. © The Royal Society of Chemistry 2012.

Chen Z.,University of Waterloo | Higgins D.,University of Waterloo | Yu A.,University of Waterloo | Zhang L.,NRC Institute for Fuel Cell Innovation | Zhang J.,NRC Institute for Fuel Cell Innovation
Energy and Environmental Science | Year: 2011

With the approaching commercialization of PEM fuel cell technology, developing active, inexpensive non-precious metal ORR catalyst materials to replace currently used Pt-based catalysts is a necessary and essential requirement in order to reduce the overall system cost. This review paper highlights the progress made over the past 40 years with a detailed discussion of recent works in the area of non-precious metal electrocatalysts for oxygen reduction reaction, a necessary reaction at the PEM fuel cell cathode. Several important kinds of unsupported or carbon supported non-precious metal electrocatalysts for ORR are reviewed, including non-pyrolyzed and pyrolyzed transition metal nitrogen-containing complexes, conductive polymer-based catalysts, transition metal chalcogenides, metal oxides/carbides/nitrides/ oxynitrides/carbonitrides, and enzymatic compounds. Among these candidates, pyrolyzed transition metal nitrogen-containing complexes supported on carbon materials (M-N x/C) are considered the most promising ORR catalysts because they have demonstrated some ORR activity and stability close to that of commercially available Pt/C catalysts. Although great progress has been achieved in this area of research and development, there are still some challenges in both their ORR activity and stability. Regarding the ORR activity, the actual volumetric activity of the most active non-precious metal catalyst is still well below the DOE 2015 target. Regarding the ORR stability, stability tests are generally run at low current densities or low power levels, and the lifetime is far shorter than targets set by DOE. Therefore, improving both the ORR activity and stability are the major short and long term focuses of non-precious metal catalyst research and development. Based on the results achieved in this area, several future research directions are also proposed and discussed in this paper. © 2011 The Royal Society of Chemistry.

Malek K.,NRC Institute for Fuel Cell Innovation | Sahimi M.,University of Southern California
Journal of Chemical Physics | Year: 2010

Silicon carbide nanotubes (SiCNTs) are new materials with excellent properties, such as high thermal stability and mechanical strength, which are much improved over those of their carboneous counterparts, namely, carbon nanotubes (CNTs). Gas separation processes at high temperatures and pressures may be improved by developing mixed-matrix membranes that contain SiCNTs. Such nanotubes are also of interest in other important processes, such as hydrogen production and its storage, as well as separation by supercritical adsorption. The structural parameters of the nanotubes, i.e., their diameter, curvature, and chirality, as well as the interaction strength between the gases and the nanotubes' walls, play a fundamental role in efficient use of the SiCNTs in such processes. We employ molecular dynamics simulations in order to examine the adsorption and diffusion of N2, H2, CO2, CH4, and n C4H10 in the SiCNTs, as a function of the pressure and the type of the nanotubes, namely, the zigzag, armchair, and chiral tubes. The simulations indicate the strong effect of the nanotubes' chirality and curvature on the pressure dependence of the adsorption isotherms and the self-diffusivities. Detailed comparison is made between the results and those for the CNTs. In particular, we find that the adsorption capacity of the SiCNTs for hydrogen is higher than the CNTs' under the conditions that we have studied. © 2010 American Institute of Physics.

Wang Y.-J.,University of British Columbia | Wang Y.-J.,NRC Institute for Fuel Cell Innovation | Wilkinson D.P.,University of British Columbia | Wilkinson D.P.,NRC Institute for Fuel Cell Innovation | Zhang J.,NRC Institute for Fuel Cell Innovation
Chemical Reviews | Year: 2011

The developments in the field of several important kinds of noncarbon supporting materials in recent years are reviewed. The challenges for developing noncarbon supporting materials are analyzed, and the possible future research directions, in particular the material preparation methods, are also proposed. To address the issue of carbon oxidation, effort has been placed on developing alternative noncarbon materials for catalyst supports. As compared to carbon-based supports, some noncarbon materials and their supported Pt-based catalysts have shown unique structures, suitable physical and chemical properties, and high catalytic activity toward fuel cell reactions such as the oxygen reduction reaction and small alcohol electrooxidation. To make noncarbon-supported Pt-based catalysts practically feasible in PEM fuel cells, material improvements in electronic conductivity, solubility, chemical/electrochemical and thermal stability, and surface area are required.

Neburchilov V.,NRC Institute for Fuel Cell Innovation | Wang H.,NRC Institute for Fuel Cell Innovation | Martin J.J.,NRC Institute for Fuel Cell Innovation | Qu W.,NRC Institute for Fuel Cell Innovation
Journal of Power Sources | Year: 2010

This paper reviews the compositions, design and methods of fabrication of air cathodes for alkali zinc-air fuel cells (ZAFCs), one of the few successfully commercialized fuel cells. The more promising compositions for air cathodes are based on individual oxides, or mixtures of such, with a spinel, perovskite, or pyrochlore structure: MnO2, Ag, Co3O4, La2O3, LaNiO3, NiCo2O4, LaMnO3, LaNiO3, etc. These compositions provide the optimal balance of ORR activity and chemical stability in an alkali electrolyte. The sol-gel and reverse micelle methods supply the most uniform distribution of the catalyst on carbon and the highest catalyst BET surface area. It is shown that the design of the air cathode, including types of carbon black, binding agents, current collectors, Teflon membranes, thermal treatment of the GDL, and catalyst layers, has a strong effect on performance. Crown Copyright © 2009.

Tsay K.-C.,NRC Institute for Fuel Cell Innovation | Zhang L.,NRC Institute for Fuel Cell Innovation | Zhang J.,NRC Institute for Fuel Cell Innovation
Electrochimica Acta | Year: 2012

In this paper, the effects of several experimental conditions, such as electrode layer binder content, conducting carbon content, electrode layer thickness, as well as electrolyte concentration, on both the specific capacitance and energy density of a BP2000 carbon-based supercapacitor are investigated using both cyclic voltammetry and a galvanic charging-discharging curve. The electrode layer studied contains Super C45 carbon as the conducting additive, PTFE as the binder, and Na 2SO 4 as the aqueous electrolyte, respectively. With the purpose of optimizing the electrode layer structure, 15 wt% of Super C45 and 5 wt% of PTFE in the electrode layer with a thickness of 100 μm, are found to be the best composition in terms of improving both specific capacitance and energy density. Regarding the effect of electrolyte concentration in the range of 0.1-1.0 M, 0.5 M of Na 2SO 4 gives the best performance. © 2011 Published by Elsevier Ltd.

Bing Y.,NRC Institute for Fuel Cell Innovation | Liu H.,NRC Institute for Fuel Cell Innovation | Zhang L.,NRC Institute for Fuel Cell Innovation | Ghosh D.,NRC Institute for Fuel Cell Innovation | Zhang J.,NRC Institute for Fuel Cell Innovation
Chemical Society Reviews | Year: 2010

In this critical review, we present the current technological advances in proton exchange membrane (PEM) fuel cell catalysis, with a focus on strategies for developing nanostructured Pt-alloys as electrocatalysts for the oxygen reduction reaction (ORR). The achievements are reviewed and the major challenges, including high cost, insufficient activity and low stability, are addressed and discussed. The nanostructured Pt-alloy catalysts can be grouped into different clusters: (i) Pt-alloy nanoparticles, (ii) Pt-alloy nanotextures such as Pt-skins/monolayers on top of base metals, and (iii) branched or anisotropic elongated Pt or Pt-alloy nanostructures. Although some Pt-alloy catalysts with advanced nanostructures have shown remarkable activity levels, the dissolution of metals, including Pt and alloyed base metals, in a fuel cell operating environment could cause catalyst degradation, and still remains an issue. Another concern may be low retention of the nanostructure of the active catalyst during fuel cell operation. To facilitate further efforts in new catalyst development, several research directions are also proposed in this paper (130 references). © The Royal Society of Chemistry 2010.

Sun C.,NRC Institute for Fuel Cell Innovation | Hui R.,NRC Institute for Fuel Cell Innovation | Roller J.,NRC Institute for Fuel Cell Innovation
Journal of Solid State Electrochemistry | Year: 2010

The composition and microstructure of cathode materials has a large impact on the performance of solid oxide fuel cells (SOFCs). Rational design of materials composition through controlled oxygen nonstoichiometry and defect aspects can enhance the ionic and electronic conductivities as well as the catalytic properties for oxygen reduction in the cathode. Cell performance can be further improved through microstructure optimization to extend the triple-phase boundaries. A major degradation mechanism in SOFCs is poisoning of the cathode by chromium species when chromium-containing alloys are used as the interconnect material. This article reviews recent developments in SOFC cathodes with a principal emphasis on the choice of materials. In addition, the reaction mechanism of oxygen reduction is also addressed. The development of Cr-tolerant cathodes for intermediate temperature solid oxide fuel cells, and a possible mechanism of Cr deposition at cathodes are briefly reviewed as well. Finally, this review will be concluded with some perspectives on the future of research directions in this area. © 2009 Springer-Verlag.

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