Entity

Time filter

Source Type

Bells Corners, Canada

Al-Othman A.,University of Ottawa | Tremblay A.Y.,University of Ottawa | Pell W.,University of Ottawa | Letaief S.,University of Ottawa | And 3 more authors.
Journal of Power Sources | Year: 2013

Composite membranes composed of modified S or Si-zirconium phosphate (ZrP), porous polytetrafluoethylene (PTFE) and, glycerol (GLY) were synthesized in this work. ZrP was precipitated via the in-situ reaction of zirconium oxychloride (ZrOCl2) with phosphoric acid (H3PO 4). Silicic acid and sulphuric acid were introduced as additives to phosphoric acid with variable Si/P or S/P mass ratios in the acid solution/suspension. The modified membranes were investigated as electrolytes for direct hydrocarbon fuel cells operating at temperatures ∼200 °C. The present work shows that adding a small amount of silicic acid to phosphoric acid enhanced the proton conductivity, i.e. by having a Si/P mass ratio of (0.01) in the acid solution/suspension, the Si-ZrP/PTFE/GLY membrane conductivity was 0.073 S cm-1. This value approached the conductivity of Nafion (0.1 S cm-1). The results also showed that adding sulphuric acid to phosphoric acid led to a significant decrease in the membrane's proton conductivity. SEM analysis results showed a porous structure of the Si-ZrP modified membranes. This porous structure combined with the high proton conductivity reported, would make them good candidates for catalyst layer supports in fuel cell applications. © 2012 Elsevier B.V. All rights reserved. Source


Al-Othman A.,University of Ottawa | Tremblay A.Y.,University of Ottawa | Pell W.,University of Ottawa | Letaief S.,University of Ottawa | And 3 more authors.
Journal of Power Sources | Year: 2010

Zirconium phosphate (ZrP) was investigated as a possible proton conductor material in direct hydrocarbon polymer electrolyte membrane (PEM) fuel cells that operate at greater temperatures than conventional PEM fuel cells. Amorphous zirconium phosphate was synthesized in this work by precipitation at room temperature via reaction of ZrOCl2 with H3PO4 aqueous solutions. The conductivity of the synthesized ZrP materials were 7.04 × 10-5 S cm-1 for ZrP oven dried in laboratory air at 70 °C and 3.57 × 10-4 S cm-1 for ZrP powder dried first at 70 °C in laboratory air and then processed at 200 °C with continuous H2O injection at an H2O/N2 molar ratio of 6. This work showed that by maintaining appropriate water content in the vapour phase at processing conditions, it was possible to alter the composition of zirconium phosphate to a sufficiently hydrated state, and thereby avoid the normal decrease in conductivity with increasing temperature. © 2009 Elsevier B.V. All rights reserved. Source


Al-Othman A.,University of Ottawa | Tremblay A.Y.,University of Ottawa | Pell W.,University of Ottawa | Liu Y.,University of Ottawa | And 2 more authors.
Journal of Power Sources | Year: 2012

Composite membranes composed of zirconium phosphate (ZrP, a proton conductor), and porous polytetrafluoroethylene (PTFE, a mechanical support for ZrP), have been studied as electrolytes for direct hydrocarbon fuel cells that might operate at temperatures approaching 200 °C. The previous literature describes membranes formed by compressing PTFE particles and ZrP particles (conductivity = 10-3 S cm-1). The results reported here show that adding glycerol (GLY) to a reaction mixture of ZrOCl 2·8H2O and H3PO4 to form ZrP in situ within the pores of PTFE, produced a membrane (conductivity = 0.02-0.045 S cm-1) that approached the performance of Nafion (conductivity = 0.1 S cm-1). The conductivity remained unchanged when one of the membranes (conductivity = 0.02 S cm-1) was processed at the inlet conditions to a direct propane fuel cell (200 °C and steam mole fraction yH2O=0.86). The composite membrane, prepared with glycerol, contained ZrP spheres (100-500 nm) that were smaller than the PTFE pore diameters (1000-2000 nm). The enhanced conductivity may have been caused by a combination of proton transport on the exterior surfaces of the ZrP solid spheres, proton hopping through the bulk of the ZrP, and proton hopping via the OH groups in glycerol. © 2011 Elsevier B.V. All rights reserved. Source


Vafaeyan S.,University of Ottawa | St-Amant A.,University of Ottawa | Ternan M.,EnPross Inc.
Journal of Chemistry | Year: 2014

High temperature polymer electrode membrane fuel cells that use hydrocarbon as the fuel have many theoretical advantages over those that use hydrogen. For example, nonprecious metal catalysts can replace platinum. In this work, two of the four propane fuel cell reactions, propane dehydrogenation and water dissociation, were examined using nickel alloy catalysts. The adsorption energies of both propane and water decreased as the Fe content of Ni/Fe alloys increased. In contrast, they both increased as the Cu content of Ni/Cu alloys increased. The activation energy for the dehydrogenation of propane (a nonpolar molecule) changed very little, even though the adsorption energy changed substantially as a function of alloy composition. In contrast, the activation energy for dissociation of water (a molecule that can be polarized) decreased markedly as the energy of adsorption decreased. The different relationship between activation energy and adsorption energy for propane dehydrogenation and water dissociation alloys was attributed to propane being a nonpolar molecule and water being a molecule that can be polarized. © 2014 Shadi Vafaeyan et al. Source

Discover hidden collaborations