Role of Ceria-Zirconia Solid Solution with High Oxygen Storage Capacity in Cermet Anodes of Solid Oxide Fuel Cells

Abstract

A solid solution of ceria and zirconia is investigated as the ceramic component of the cermet anode for solid oxide fuel cells (SOFCs). Homogeneously dispersed NiO-Ce0.75Zr0.25O2-delta (CZO) composite powder is synthesized via a single-step combustion process based on the glycine-nitrate-method. The electrolyte-supported cell composed of a Ni - CZO anode, yttria-stabilized zirconia (YSZ) electrolyte and La-0 6Sr0 4Co0.2Fe0 O-8(3) (LSCF) - gadolinia-doped ceria (GDC) cathode is fabricated, and its electrochemical performance is compared with that of a reference cell employing the conventional Ni-YSZ anode. The Ni-CZO anode exhibits substantially higher performance than the Ni-YSZ anode, indicating that CZO actively participates in the anode's catalytic process, in contrast to YSZ. Impedance spectra of full-cells and half-cells are correlated to understand the electrode reaction mechanisms, and heavily overlapping impedance arcs are successfully deconvoluted using a differential relaxation time (DRT) technique. It is found that CZO promotes fuel oxidation through an oxygen spillover mechanism and enhances gas-solid interaction via H-2 adsorption on the ceramic component of the cermet anode, resulting in a reduction of the electrode polarization resistance. The potential of the Ni-CZO anode for practical applications and a strategy for further development are discussed in detail. (C) 2014 The Electrochemical Society. All rights reserved.