Effects of changes in solid oxide fuel cell electrode thickness on ohmic and concentration polarizations

Abstract

In order to address the shortcomings of the solid oxide fuel cell (SOFC) associated with the thin electrode, the anode-cathode-supported SOFC (ACSC) is proposed in this study. In the ACSC, the electrolyte is thin, while both the anode and cathode have enough thickness to act as self-supporting layers. The mathematical models of both the anode-supported SOFC (ASC) and ACSC are established, which capture the intricate interdependency among the charge and gas transport, and the electrochemical reactions. The validity of the mathematical model is preliminarily verified by the good agreement between the numerical and experimental I-V curves of the ASC button cell. For the same base case parameters and operating conditions, the average current density of ASC is 6388 A m-2 , only 83% of the ACSC, 7713 A m-2. The advantages of ACSC mainly stem from two aspects: i) the increased oxygen concentration under the solid rib covered zone, which extends the reaction active zone; ii) the increased cross section of the electric current transport path, which greatly decreases the cathode ohmic polarization. The performance comparison between the ACSC and ASC are examined by systematically varying the cathode electric conductivity, porosity, tortuosity factor and the output voltage. The results indicated that the advantage of ACSC over ASC is always obvious although the performance of ACSC varies with different parameters.

A Theoretical Model for the Triple Phase Boundary of Solid Oxide Fuel Cell Electrospun Electrodes

“…where el r are the radii of the electron-conducting particles in the shell; 0 α is the contact angle between the fibers and particles, which is 15° [40,41]; io-el Z is the coordination number between the Figure 2. The schematic diagram of the case in which the shell is smaller than one layer, (a) the particles are randomly dispersed on the fiber face and some particles do not percolate in the red oval frame and (b) shows the schematic after deleting the particles that do not percolate.…”

“…where r el are the radii of the electron-conducting particles in the shell; α 0 is the contact angle between the fibers and particles, which is 15 • [40,41]; Z io−el is the coordination number between the fibers and particles in the repeating unit; n v is the number of repeating units per unit volume; p io is the percolation ratio of the ion-conducting fibers; and p el is the percolation ratio of the electron-conducting particles. is the percolation ratio of the ion-conducting fibers; and el p is the percolation ratio of the electronconducting particles.…”

Thickness‐dependent high‐performance solid oxide fuel cells with Ba0.5Sr0.5Co0.8Fe0.2O3‐δ cathode

“…Different from the Carnot cycle, SOFCs can achieve the direct conversion of the chemical fuels not involving any mechanical aspects, guaranteeing the high conversion efficiency 5 . Normally, a single SOFC is made up of an anode and a cathode, which are separated by an electrolyte 6,7 . Low‐cost and long‐term stable electrode materials are highly desirable for the commercial application of SOFCs within the operating temperature of 600–800°C, or even below 600°C 8–12 .…”

“…5 Normally, a single SOFC is made up of an anode and a cathode, which are separated by an electrolyte. 6,7 Low-cost and long-term stable electrode materials are highly desirable for the commercial application of SOFCs within the operating temperature of 600-800 C, or even below 600 C. [8][9][10][11][12] However, SOFCs operating at lower temperatures can unfortunately lead to the poor cell performance, which can be attributed to the increase of cathodic polarization losses. 13 The low ion conductivity of the traditional cathode material La 0.8 Sr 0.2 MnO 3 (LSM) stimulates great efforts at the moment on cobalt-containing mixed oxygen ionic and electronic conductors (MIECs) because of their excellent electrocatalytic activity and high electrical conductivity towards oxygen reduction reaction (ORR) at intermediate temperatures (IT) 14,15 and thus can be served as active cathodes for IT-SOFCs.…”

Electrochemical performance of yttria‐doped SrCoO3‐δas cathode material for anode‐supported solid oxide fuel cell

“…The performance of SOFCs is affected by multiple voltage losses, attributed to the ohmic polarization loss, activation polarization loss, and concentration polarization loss. The ohmic polarization is a prominent part of the total polarization loss 11–14 . Significant efforts have been made to minimize the electrolyte's ohmic resistance.…”