Classification Criteria for Solid Oxide Fuel Cell Electrode Materials

Abstract

In an attempt to establish comparison criteria for the electrocatalytical properties of electrode materials, systematic measurements were carried out on microelectrodes of simple shapes. The overpotential resistances were normalized with respect to the electrode triple‐phase boundary length and the electrode capacitances to the electrode interface area. Results obtained on metals such as Ag, Pt, Au, and Ni, and on some oxides, under either cathodic or anodic atmospheres, show marked differences which allow us to classify them. The positions of several materials in the cathode and anode material lists can be significantly different, indicating different electrocatalytical requirements under solid oxide fuel cell cathode and anode atmospheres. The clearest example is silver, which exhibits excellent electrocatalytical properties for the oxygen electrode reaction and very poor properties for hydrogen oxidation.

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

“…Silver exhibits excellent electrocatalytic properties in oxygen reduction reaction (ORR) and the lowest cathodic overpotential resistance (among Ag, Au, Pt, LSC, LSM, LSCF, and La 0.6 Sr 0.4 Fe 0.8 Mn 0.2 O 3 ) [15]. Pure silver is not used as a cathode in SOFC due to its disadvantages.…”

“…These measurements have been performed using point electrodes [5,6,15,18,[52][53][54], porous electrodes in a symmetrical cell [55][56][57][58][59], or three-electrode setup [60][61][62].…”

Silver migration at the Ag|Sm0.2Ce0.8O1.9 interface

“…One of the methods used to improve the performance of oxide cathodes is the addition of noble metals. Silver shows the best catalytic activity in the oxygen reduction reaction (ORR) [1], while its price is the lowest among the noble metals. Several composite materials containing silver and oxide cathode material, such as La 0.6 Sr 0.…”

“…A quasi-point electrode is a powerful tool to study ORR [1,22,23] and the migration of noble metals [5,[17][18][19][20] due to its simplified geometry. Jacobsen et al [24,25] examined a platinum quasi-point electrode contacting an yttria-stabilized zirconia (YSZ) electrolyte.…”

Aspects of Metal-YSZ Electrode Kinetics Studied using Model Electrodes

“…Therefore, this work makes a comparative characterization of the electrode kinetics of several metals (such as Ni, Cu, Pt, etc) as the negative electrode of a solid oxide cell, using model wire electrodes contacting a yttria-stabilized zirconia (YSZ) pellet electrolyte. In comparison to studies with model negative-electrodes using some of the same metals [1,2], we use additional H 2 O-or CO 2 -rich gas atmospheres relevant to electrolysis of H 2 O and CO 2 , and we study the dynamics of the materials in these conditions at open circuit voltage (OCV) and under polarization.…”