Porous Catalytic Layer Research Articles

Mass transfer in porous systems, flooded in part with water, of gas diffusion and catalytic layers of the cathode of a fuel cell with a solid polymer electrolyte

Mass transfer in porous gas diffusion and catalytic layers of the cathode of a hydrogen-air fuel cell with a solid polymer electrolyte is considered. The transport processes are considered with allowance made for the partial flooding of porous systems of these layers with water, which forms during the fuel cell operation. The consideration also allows for the influence of the diluent gas present when air oxygen is used as the oxidant. The fraction of water-flooded pores is calculated within percolation theory as a function of structural parameters of the porous system. Conditions leading to the beginning of the gas diffusion layer flooding are presented.

Synthesis of Highly Porous Catalytic Layers for Polymer Electrolyte Fuel Cell Based on Carbon Aerogels

Recent studies of the PEMFC catalytic layer electrocatalyst support showed that high surface area carbon blacks cannot be used efficiently (1) because they have necessarily small primary pores that yield high diffusion limitation for the oxygen reduction reaction (ORR). In the present paper, we first synthesized and characterized carbon aerogels which exhibit high surface area, high porous volume and adjustable pore-size distribution. In that way, they enable to decouple between surface area and porosity, while they are also promising electrocatalyst supports (2). Second, we elaborated new catalytic layers made from 2 different carbon aerogels with 2 different Nafion loadings. Finally, we characterized the structure of such catalytic layers, and evaluated their activity towards the oxygen reduction reaction (ORR). Finally, an appropriate catalyst support should display large pore-size and high surface area in order to reduce the PEMFC cathode platinum loadings without loosing activity, following the reduction of oxygen diffusion limitation.

Synthesis of Highly Porous Catalytic Layers for Polymer Electrolyte Fuel Cell Based on Carbon Aerogels

not Available.

Catalytic effects in oxygen permeation through mixed-conductive LSCF perovskite membranes

Abstract The porous catalytic layer of perovskites was coated on either surface or both surfaces of the dense membranes of LSCF perovskites with nearly 1-mm thickness, and the catalytic effects on the oxygen permeation flux under the air/He gradient were investigated. The observed catalytic effects were discussed mainly on the basis of the oxygen sorption–desorption capacity (OSDC) of membrane and catalyst materials. The coating on the anode side improved the oxygen flux in any combinations of the membrane and catalyst materials having different OSDC, and an increase in the anode surface area, where oxygen association reaction takes place, is primarily responsible for the enhancement by the anode coating. The effect of the cathode coating, on the other hand, depended significantly on the relative difference in OSDC of the membrane and catalyst materials: for example, the oxygen permeation flux was enhanced and reduced by coating with perovskites having larger and smaller OSDC, respectively. It has turned out that the cathode materials should have large OSDC. The behavior of membranes modified on both sides could be understood in terms of a simple sum of the cathodic and anodic effects.

Ruthenium oxide for effective activation of aluminium sacrificial anodes: a new approach

Ruthenium oxide, one of the excellent electrocatalysts having high conductivity and high chemical and thermodynamic stability, has been coated onto the surface of an electrode made from a Al–5 wt-%Zn alloy. The activated aluminium ion was able to diffuse through the porous catalytic hydrophilic layer. Ruthenium oxide coated Al–Zn alloy anodes displayed high open circuit potential and high closed circuit potential during galvanic exposure with mild steel cathodes. A galvanic efficiency as high as 86% with an actual current capacity of 2573 A h kg-1 was achieved. The RuO2 film underwent very little deterioration and a considerable mass of the ruthenium oxide film persisted on the anode surface, even after the electrode size had been reduced to one third of its original size owing to galvanic dissolution. These electrodes are economically efficient, as convenient to prepare, install and use as other conventional electrodes, are tolerable of very aggressive media and highly efficient, even under high galvanic current loads.

Amperometric gas‐diffusion/enzyme electrode

AbstractAn amperometric enzyme gas‐diffusion electrode has been developed which combines a porous, air breathing gas‐diffusion electrode with an enzyme [glucose oxidase (GOD)] immobilized with Nation into its porous catalytic layer. The catalytic layer contains pyrolyzed Co‐ tetramethoxyphenylporphyrine (CoTMPP), which is very active towards the electrochemical oxidation of H2O2. The behavior of this electrode was investigated when the oxygen needed for the enzymatic reaction was supplied from the air (in the gas phase) through the porous structure of the gas‐diffusion electrode. It was shown that in the presence of the substrate (glucose), the amperometric signal obtained in this mode of operation was much higher than that obtained when only the oxygen dissolved in the electrolyte was involved in the enzymatic reaction. The developed enzyme gas‐diffusion electrode allows a versatile and rapid change in the O2 concentration in the zone where the enzymatic reaction is taking place. This electrode can be used as a model system for the investigation of the influence of O2 on the performance of both the peroxide or the mediated enzyme electrodes in an effort to develop oxygen independent biosensors.

MODELING AND SIMULATION OF A NONISOTHERMAL CATALYTIC MEMBRANE REACTOR

Abstract A two-dimensional nonisothermal mathematical model has been developed to simulate a tube-and-shell configuration, catalytic membrane reactor. The three-layer membrane consists of an inert large-pore support, an o2 semipermeable dense perovskite layer and a porous catalytic layer. The model is applied to the simulation of the partial oxidation or methane to syngas (oxyreforming). The membrane reactor simultaneously supplies oxygen to the catalytic reaction along the reactor length, and separates oxygen from the air feed, using a dense perovskite layer which is a mixed conductor, thus allowing rapid oxygen permeation without the use of an external circuit. Two configurations of catalytic membrane reactors are simulated, for both bench-scale and industrial-scale conditions. Comparisons are made to the conventional fixed-bed reactor, and to membrane reactors which are isothermal, adiabatic or wall-cooled. The simulation results imply that the temperature rise in exothermic partial oxidation reactions may be mitigated substantially by the use of a dense membrane reactor,

Mathematical models of the monolith catalytic converter: Part I. Development of model and application of orthogonal collocation

AbstractThe orthogonal collocation method is applied to solve the mathematical model of a monolith catalytic converter, in which the reaction takes place in a porous catalytic layer deposited on the wall of a tube. A sequence of models is developed, with the most complicated one involving transient heat and mass transfer in three dimensions.