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Improvement of Cathode Material for Solid Oxide Fuel Cell through Surface Infiltration and Electrospinning


Type

Thesis

Change log

Authors

Gao, Chenlong 

Abstract

In this study, two methods have been used to enhance the catalytic property of the La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO; LSCF:CGO = 1:1) cathode in solid oxide fuel cell applications. One method involved altering the surface of the LSCF/CGO by including metal oxide nanoparticles. By utilizing an infiltration approach, Co3O4, NiO and CuO nanoparticles with a particle size of 10–20 nm has been effectively deposited onto the surface of the LSCF/CGO composite cathode.

The as infiltrated cathode showed significant reduction in the overall area-specific resistance (ASR) at 500oC (1.72Ω•cm2, 2.5Ω•cm2, and 3.9Ω•cm2 respectively), which was nearly 4-10 times smaller than the non-infiltrated LSCF/CGO (15.5Ω•cm2) at 500oC. The enhanced electro-catalytic active sites that these nano decorations on the cathode's surface can provide were ascribed to this improvement. It was discovered that these metal oxides increased the density of reaction sites on the surface, encouraging improved surface oxygen ion exchange sites at the interface between the basic cathode materials and the catalytic oxides. The oxygen ions supplied by these metal oxides assisted in reducing the oxygen vacancy concentration on the surface of LSCF and suppressing the Sr surface segregation, which was verified by SEM and XPS, therefore slowing the pace of cell performance degradation. Impedance experiments utilizing symmetrical cells, where the performance degradation rate of LSCF/CGO at 500oC dramatically decreased because of Co3O4, NiO, and CuO nanoparticles metal oxide infiltration, verified the cathode's performance.

In this work, it has also been recognized how the silver particles on the LSCF/CGO surface affect the cell's overall catalytic properties. The silver current collector was also discovered to be partially responsible for the decline in cell function with age. By infiltrating Co3O4 nanoparticles into both the silver current collector and the LSCF/CGO, the cell degradation rate declined from 1.78 Ω•cm2/hour to 0.06 Ω•cm2/hour at 500oC. In a different method, an electro-spun cathode was employed in place of a conventional powder-formed cathode. This cathode had a fibrous structure. By meticulously regulating the electrospinning parameters, such as voltage, solution concentration, and the distance between the needle and the collector, the method of creating nanofibres has been researched and perfected. By coating the electrolyte with uniform CGO fibres covered with LSCF nanoparticles, a cathode was created. The fibrous cathode demonstrated much reduced ASR (about 5 times smaller) than the powder-formed cathode in the temperature range of 500oC to 650oC. It has also been researched and adjusted how the loading of LSCF affects CGO fibre. The quantity of LSCF has been proposed by modeling and experimental evidence.

Description

Date

2017-07-28

Advisors

Kumar, Ramachandran

Keywords

Cathode, electrospinning, SOFC

Qualification

Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge