Tailoring Ni and Sr2Mg0.25Ni0.75MoO6−δ Cermet Compositions for Designing the Fuel Electrodes of Solid Oxide Electrochemical Cells

Lubov S Skutina,Dmitry K Kuznetsov,Dmitry A Medvedev,Aleksey A Vylkov,Vladimir Ya Shur

doi:10.3390/en12122394

Lubov S Skutina, Dmitry K Kuznetsov + Show 3 more

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https://doi.org/10.3390/en12122394

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Abstract

The design of new electrode materials for solid oxide electrochemical cells, which are stable against redox processes as well as exhibiting carbon/sulphur tolerance and high electronic conductivity, is a matter of considerable current interest as a means of overcoming the disadvantages of traditional Ni-containing cermets. In the present work, composite materials having the general formula (1−x)Sr2Mg0.25Ni0.75MoO6−δ + xNiO (where x = 0, 15, 30, 50, 70 and 85 mol.%) were successfully prepared to be utilised in solid oxide fuel cells. A detailed investigation of the thermal, electrical, and microstructural properties of these composites, along with their phase stability in oxidising and reducing atmospheres, was carried out. While possessing low thermal expansion coefficient (TEC) values, the composites having low Ni content (15 mol.%–70 mol.%) did not satisfy the requirement of high electronic conductivity. Conversely, the 15Sr2Mg0.25Ni0.75MoO6−δ + 85NiO samples demonstrated very high electrical conductivity (489 S sm−1 at 850 °C in wet H2) due to well-developed Ni-based networks, and no deterioration of thermal properties (TEC values of 15.4 × 10−6 K−1 in air and 14.5 × 10−6 K−1 in 50%H2/Ar; linear expansion behaviour in both atmospheres). Therefore, this material has potential for use as a component of a fuel cell electrode system.

Highlights

Solid oxide fuel cells (SOFC) are electrochemical devices capable of converting hydrogen and more readily available carbon-containing fuels into electricity with high efficiency and low emissions [1,2,3,4].Traditional SOFC systems based on yttria-stabilised zirconia (YSZ) electrolytes operate at very high temperatures required for reaching the sufficient performance [5,6]
Such high temperatures impede the commercialisation of SOFCs due to the rapid component degradation associated with chemical and microstructural factors [7,8,9,10]
SOFCs, new challenges emerge in the course of developing the high-performance materials on which they are based

Summary

Introduction

Traditional SOFC systems based on yttria-stabilised zirconia (YSZ) electrolytes operate at very high (more than 800 ◦ C) temperatures required for reaching the sufficient performance [5,6]. Such high temperatures impede the commercialisation of SOFCs due to the rapid component degradation associated with chemical (interdiffusion, chemical reactivity) and microstructural (electrolyte recrystallisation, electrode particle agglomeration, functional material delamination) factors [7,8,9,10]. Sulphur poisoning and carbon coking on the Ni-based

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