Porous Solid Oxide Fuel Cell Research Articles

Effect of Porous Microstructural Properties on the Results of a Cell-Level Model in Solid Oxide Fuel Cells

A detailed micro-model framework is used for calculating effective micro-structural properties for the porous anode and cathode electrodes in solid oxide fuel cells (SOFCs). The resulting micro-structural parameters obtained from this detailed numerical approach are then applied to a macro-scale SOFC cell model. The performance of the SOFC cell model is determined by the geometric and effective transport micro-structural properties which properly accounting for representative porous SOFC electrode structures.

A modeling study of porous composite microstructures for solid oxide fuel cell anodes

AbstractA model of porous composite microstructures for solid oxide fuel cell (SOFC) anodes, based on spherical particle packing, was numerically studied by means of the three-dimensional particle element method (PEM), which is a discrete element method. In this model, the porous SOFC consisted of three-component particles: electronic, ionic and void particles (pores). A triple-phase boundary (TPB) was defined by the local site where the three-component phases came into contact. The length of TPB (TPB density) was calculated by the contact circle length between the ionic and electronic particles at the TPB site. In the present study, the effect of porosity could be treated in addition to the grain size of the solid phase. Because the effect of porosity was treated in detail, our numerical results were in good agreement with the experimentally measured TPB density.

ChemInform Abstract: Characterization, Modeling, and Optimization of Transport and Reaction Processes in the Porous Solid Oxide Fuel Cell Anode

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

H2-H2O Effective Binary Diffusivity Measurement in Solid Oxide Fuel Cell Anode Using an Electrochemical Cell

The effective binary diffusivity of H2 and H2O in a Ni and yittria-stabilized zirconia (YSZ) anode of the solid oxide fuel cells (SOFCs) was measured between 650 and 800oC using an electrochemical cell consisting of an oxygen pump, an oxygen sensor, and a porous SOFC anode pellet. The effective binary diffusivity was obtained from the relationship between the current density across the oxygen pump, and the H2 partial pressure gradient across the anode sample measured using the oxygen sensor. The anode limiting current density and concentration polarization were estimated using the experimental results.

Out-of-cell measurements of H 2–H 2O effective binary diffusivity in the porous anode of solid oxide fuel cells (SOFCs)

The effective binary diffusivity of H 2 and H 2O in a Ni and yittria-stabilized zirconia (YSZ) anode of the solid oxide fuel cells (SOFCs) was measured between 650 and 800 °C using an electrochemical cell consisting of an oxygen pump, an oxygen sensor, and a porous SOFC anode pellet. The effective binary diffusivity was obtained from the relationship between the current density across the oxygen pump, and the H 2 partial pressure gradient across the anode sample measured using the oxygen sensor. The anode limiting current density and concentration polarization were estimated using the experimental results.

Nanostructured thin solid oxide fuel cells with high power density

Nanostructured thin film solid oxide fuel cells (SOFC) have been developed for reduced temperature operation, with high power density, and to be self reforming. A thin film electrolyte (1-2 microm thickness), e.g., yttria-stabilized zirconia (YSZ), is deposited on a nickel foil substrate. The electrolyte thin film is polycrystalline when deposited on a polycrystalline nickel foil substrate, and is (100) textured when deposited on an atomically textured nickel foil substrate. The Ni foil substrate is then converted into a porous SOFC anode by photolithographic patterning and etching to develop porosity. A composite La(0.5)Sr(0.5)CoO(3) cathode is then deposited on the thin film electrolyte. The resultant thin film hetero structure fuel cells have operated at a significantly reduced temperature: as low as 470 degrees C, with a maximum power density of 140 mW cm(-2) at 575 degrees C, and an efficiency of >50%. This drastic reduction in operating temperature for an SOFC now also allows for the use of hydrocarbon fuels without the need for a separate reformer as the nickel anode effectively dissociates hydrocarbons within this temperature range. These nanostructured fuel cells show excellent potential for high power density, small volume, high efficiency fuel cells for power generation applications.

Porous SOFC Anodes Prepared by Sublimation of an Immiscible Metal Oxide during Sintering

Nanostructured composite powder, consisting of 20 wt % SnO 2 , 50 wt % NiO, and 30 wt % Gd 0.1 Ce 0.9 O 2 (GDC), was prepared using a combustion chemical vapor deposition process from a single solution containing all precursors. Bilayer solid oxide fuel cells (SOFC) anodes of different porosity were fabricated by copressing of NiO-GDC powder and SnO 2 -NiO-GDC composite powder. Porosity variation in the anodes was achieved by the removal of the SnO 2 -phase during firing and subsequent cell testing. Anode-supported SOFC single cells were constructed and tested for electrochemical performance. Interfacial polarization resistances of a cell with the bilayer anode were 1.20, 0.49, 0.22, and 0.1 Ω cm 2 at 500, 550, 600, and 650°C, respectively, demonstrating peak power densities of 171, 301, 441, and 544 mW/cm 2 , respectively.

Correlated Resistor Network Study of Porous Solid Oxide Fuel Cell Anodes

A resistor network model is developed for solid oxide fuel cell (SOFC) composite anodes, in which solid electrolyte grains, metal particles, and pores are considered on the same footing. The model is studied by a Monte Carlo simulation on a face‐centered cubic lattice, with a random distribution of the three components over the lattice sites. The concept of active bonds is used; the bond between a metal and an electrolyte site is conductive (reaction‐active) if the sites belong to clusters connected to the solid‐electrolyte membrane or metal current collector, respectively, and if the bond has at least one neighbor site which is a part of a pore cluster connected with the fuel supplying gas channels. Active bonds are characterized by an elementary reaction resistance, inactive bonds are blocking. The total inner resistance of the anode is calculated as a function of composition and the elementary reaction resistance, Rr, vs. ion transport resistance, Re (of a “bond” between two solid‐electrolyte grains). Compositions which provide the lowest inner resistance for a given Rr/Re ratio are revealed. Across‐the‐sample distribution of the current through the three‐phase boundary is investigated. The higher the Rr/Re ratio, the larger areas of the three‐phase boundary are used; however, if the ratio is low, the reaction occurs only very close to the anode /membrane interface to avoid ion transport limitations. A scaling law for the reaction penetration depth inside the anode, (where β ⩽ 0.5) is suggested in accordance with the Monte Carlo results. In line with the existing experimental data, the simulation and scaling estimates reveal the interplay between the reaction penetration depth and the anode thickness, which determines the thickness effect on the inner resistance.