ChemInform Abstract: REACTION PATHWAYS AND POISONS PART 2, THE RATE CONTROLLING STEP FOR ELECTROCHEMICAL OXIDATION OF HYDROGEN ON PT IN ACID AND POISONING OF THE REACTION BY CO

Vogel, Wolfgang; Lundquist, Joseph T.; Ross, Philip N.; Stonehart, P.

doi:10.1002/chin.197519023

Cited by 29 publications

(50 citation statements)

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“…Typically, the dependence on the activity of the proton(H)-membrane(M) complex is not shown since the electrolyte is a polymer of defined acid concentration (i.e., c HM = c ref HM 113,114 ; in such cases, the kinetic equation is altered depending on the mechanism 89 (e.g., by the use of a surface adsorption term). However, more mechanistic-based equations are typically only used for specific studies and models and are beyond the scope of this review.…”

Section: Basic Governing Equationsmentioning

confidence: 99%

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A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

509

394

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Polymer-electrolyte fuel cells are a promising energy-conversion technology. Over the last several decades significant progress has been made in increasing their performance and durability, of which continuum-level modeling of the transport processes has played an integral part. In this review, we examine the state-of-the-art modeling approaches, with a goal of elucidating the knowledge gaps and needs going forward in the field. In particular, the focus is on multiphase flow, especially in terms of understanding interactions at interfaces, and catalyst layers with a focus on the impacts of ionomer thin-films and multiscale phenomena. Overall, we highlight where there is consensus in terms of modeling approaches as well as opportunities for further improvement and clarification, including identification of several critical areas for future research. Fuel cells may become the energy-delivery devices of the 21 st century. Although there are many types of fuel cells, polymer-electrolyte fuel cells (PEFCs) are receiving the most attention for automotive and small stationary applications. In a PEFC, fuel and oxygen are combined electrochemically. If hydrogen is used as the fuel, it oxidizes at the anode releasing proton and electrons according toThe generated protons are transported across the membrane and the electrons across the external circuit. At the cathode catalyst layer, protons and electrons recombine with oxygen to generate waterAlthough the above electrode reactions are written in single step, multiple elementary reaction pathways are possible at each electrode. During the operation of a PEFC, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. * Electrochemical Society Active Member. z E-mail: azweber@lbl.govOver the last several decades significant progress has been made in increasing PEFC performance and durability. Such progress has been enabled by experiments and computation at multiple scales, with the bulk of the focus being on optimizing and discovering new materials for the membrane-electrode-assembly (MEA), composed of the proton-exchange membrane (PEM), catalyst layers, and diffusionmedia (DM) backing layers. In particular, continuum modeling has been invaluable in providing understanding and insight into processes and phenomena that cannot be resolved or uncoupled through experiments. While modeling of the transport and related phenomena has progressed greatly, there are still some critical areas that need attention. These areas include modeling the catalyst layer and multiphase phenomena in the PEFC porous media.While there have been various reviews over the years of PEFC modeling 1-7 and issues, [8][9][10][11][12][13][14] as well as numerous books and book chapters, there is a need to examine critically the field in terms of what has been done and what needs to be done. This review serves that purpose with a focus on transport modeling of PEFCs. This is not meant to be an exhaustive review...

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Section: Basic Governing Equationsmentioning

confidence: 99%

“…159,311,312,336,337 For accounting for transport into and through the film, a two-stage process is used, comprised of transport through the film [114] and the slow oxygen dissolution process at the gas/ionomer interface, 266,338,339 …”

Section: Catalyst-layer Modelingmentioning

confidence: 99%

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

509

394

View full text Add to dashboard Cite

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“…Due to insufficient data on hydrogen solubility in phosphoric acid at high temperature, hydrogen solubility International Journal of Electrochemistry was considered similar to that of oxygen [39] at the same conditions (pressure, temperature and phosphoric acid concentration).…”

Section: Transport Through Thin Film Electrolytesmentioning

confidence: 99%

“…The rate determining step for hydrogen oxidation is the dissociation reaction (Volmer) giving rise to the secondorder dependency of hydrogen oxidation rate on surface coverage and Vogel et al [39] suggested the following equation:…”

Section: Phosphoric Acid Concentration Temperature and Watermentioning

confidence: 99%

“…The conductivity obtained from (39) along with the membrane thickness of (40 μm) were used to determine the IR losses through the membrane. On the other hand the IR losses (protonic) through the catalyst layer were obtained from the catalyst layer thickness (15 μm) and the effective phosphoric acid conductivity (product of phosphoric acid conductivity at the studied condition and its volume fraction in the electrode).…”

Section: Conductivity and Ir Lossesmentioning

confidence: 99%

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A High Temperature Polymer Electrolyte Membrane Fuel Cell Model for Reformate Gas

Mamlouk

Sousa

Scott

2011

International Journal of Electrochemistry

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A one-dimensional model of a high temperature polymer electrolyte membrane fuel cell using polybenzimidazole (PBI) membranes is described. The model considers mass transport through a thin film electrolyte covering the catalyst particles as well as through the porous media. The incorporation of a thin film model describing reactant gas mass transport through electrolyte covering the electrocatalyst is shown to be an essential requirement for accurate simulation. The catalyst interface is represented using a macrohomogeneous model. The influence of carbon monoxide, carbon dioxide, and methane, which would be present in a reformate gas, is considered in terms of the effect on the anode polarisation/kinetics behaviour. The model simulates the influence of operating conditions, cell parameters, and fuel gas compositions on the cell voltage current density characteristics. The model gives good predictions of the effect of oxygen and air pressures on cell behaviour and correctly simulates the mass transport behaviour of the cell. The model with reformate gas shows that additional voltage losses associated with CO poisoning can lead to loss in voltage of tens of mV and thus reduction in power.

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“Development of Advanced Noble Metal‐Alloy Electrocatalysts for Phosphoric Acid Fuel Cells (PAFC)”

Stonehart¹

1990

Ber Bunsenges Phys Chem

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Catalysis 1 Colloid Particles Electrocatalysis J Electrochemistry J Fuel CellsIn the preparation of highly dispersed noble metal electrocatalysts, the technology is such that crystallites now can be routinely prepared with small dimensions so that 50% of the atom content resides at the particle surface. The crystallite diameters are of the order of 12 Angstrmn (1.2 nanometers). Operation of these materials, when applied to phosphoric acid fuel cells as electrocatalysts is, of course, critical. What is important is the realization that due to the high surface energies of these crystallites, they have properties that are unlike the properties of the bulk metals. Although this manufacturing achievement is very great, more recently there has been increased emphasis on preparing alloys of metals with platinum in order to increase the kinetic rate of reaction for the oxygen reduction. -For oxygen reduction, binary alloys of platinum with refractory metals such as vanadium showed higher activity, but the vanadium was rapidly leached out. Alloys with chromium and subsequently with the addition of cobalt to form ternary alloys have now exhibited greater resistance to degradation. These alloys are hard and resistant to sintering, until the alloying element is leached out, then crystallite growth is obtained. -More recently, process modifications to produce ordered alloys have shown stability for over 9000 hours in the hot phosphoric acid fuel cell environment, as have alloys of platinum with cobalt and/or chromium containing gallium additions. It is one theory that there is no catalytic enhancement for oxygen reduction due to these alloying elements, but the increased reactivity is due solely to leaching out of the alloying elements from the alloy surface to produce a microroughness in the platinum crystallite. -In the case of hydrogen oxidation, especially in the presence of electrocatalyst poisons such as carbon monoxide and hydrogen sulphide, alloys of platinum with palladium show greater tolerance to poisoning and greater stability against crystallite growth. Other alloys are now under development to lower the catalyst cost and increase the electrocatalyst performance. This work is coupled with developments of advanced theoretical models that are amenable to computer solution for the operation of gas-diffusion electrodes to maximize both the catalyst utilization within the electrode structure, and within the cell stack.

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ChemInform Abstract: REACTION PATHWAYS AND POISONS PART 2, THE RATE CONTROLLING STEP FOR ELECTROCHEMICAL OXIDATION OF HYDROGEN ON PT IN ACID AND POISONING OF THE REACTION BY CO

Abstract: Elektrochemische Daten (cyclische Voltammetrie, anodische H,‐Polarisation) werden mit Daten des H, ‐D,‐Austauschs in der Gasphase verglichen.

Cited by 29 publications

References 1 publication

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

A High Temperature Polymer Electrolyte Membrane Fuel Cell Model for Reformate Gas

“Development of Advanced Noble Metal‐Alloy Electrocatalysts for Phosphoric Acid Fuel Cells (PAFC)”

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