Hydrocarbon Compatible SOFC Anode Catalysts and Their Syntheses: A Review

With the fast depleting rate of fossil fuels, the whole world is looking for promising energy sources for the future, and fuel cells are perceived as futuristic energy sources. Out of the different varieties of fuel cells, solid oxide fuel cells (SOFCs) are promising due to their unique multi-fuel operating capability without the need for an external reformer. Nonetheless, the state-of-the-art anode material Ni–YSZ undergoes carburization in presence of hydrocarbons (HCs), resulting in performance degradation. Several strategies have been explored by researchers to overcome the issue of carburization of the anode. The important strategies include reducing SOFC operating temperature, adjustment of steam: carbon ratio, and use of alternate anode catalysts. Among these, the use of alternate anodes is a promising strategy. Apart from the carburization issue, the anode can also undergo sulfur poisoning. The present review discusses carburization and sulfur poisoning issues and the different strategies that can be adopted for tackling them. The quintessence of this review is to provide greater insight into the various developments in hydrocarbon compatible anode catalysts and into the synthesis routes employed for the synthesis of hydrocarbon compatible anodes.

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Undoped Sr2MMoO6 Double Perovskite Molybdates (M = Ni, Mg, Fe) as Promising Anode Materials for Solid Oxide Fuel Cells

Materials ◽

10.3390/ma14071715 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1715

Author(s):

Lubov Skutina ◽

Elena Filonova ◽

Dmitry Medvedev ◽

Antoine Maignan

Keyword(s):

Fuel Cells ◽

Solid Oxide Fuel Cells ◽

Anode Materials ◽

Functional Materials ◽

Double Perovskite ◽

Solid Oxide ◽

Sulfur Poisoning ◽

Oxide Fuel ◽

Fundamental Properties ◽

Main Emphasis

The chemical design of new functional materials for solid oxide fuel cells (SOFCs) is of great interest as a means for overcoming the disadvantages of traditional materials. Redox stability, carbon deposition and sulfur poisoning of the anodes are positioned as the main processes that result in the degradation of SOFC performance. In this regard, double perovskite molybdates are possible alternatives to conventional Ni-based cermets. The present review provides the fundamental properties of four members: Sr2NiMoO6-δ, Sr2MgMoO6-δ, Sr2FeMoO6-δ and Sr2Fe1.5Mo0.5O6-δ. These properties vary greatly depending on the type and concentration of the 3d-element occupying the B-position of A2BB’O6. The main emphasis is devoted to: (i) the synthesis features of undoped double molybdates, (ii) their electrical conductivity and thermal behaviors in both oxidizing and reducing atmospheres, as well as (iii) their chemical compatibility with respect to other functional SOFC materials and components of gas atmospheres. The information provided can serve as the basis for the design of efficient fuel electrodes prepared from complex oxides with layered structures.

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Direct-Hydrocarbon Proton-Conducting Solid Oxide Fuel Cells

Sustainability ◽

10.3390/su13094736 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4736

Author(s):

Fan Liu ◽

Chuancheng Duan

Keyword(s):

Fuel Cells ◽

Solid Oxide Fuel Cells ◽

Solid Oxide ◽

Sulfur Poisoning ◽

Oxide Fuel ◽

Power Sources ◽

Proton Conducting ◽

Conducting Oxides ◽

Operating Temperatures ◽

Ion Conducting

Solid oxide fuel cells (SOFCs) are promising and rugged solid-state power sources that can directly and electrochemically convert the chemical energy into electric power. Direct-hydrocarbon SOFCs eliminate the external reformers; thus, the system is significantly simplified and the capital cost is reduced. SOFCs comprise the cathode, electrolyte, and anode, of which the anode is of paramount importance as its catalytic activity and chemical stability are key to direct-hydrocarbon SOFCs. The conventional SOFC anode is composed of a Ni-based metallic phase that conducts electrons, and an oxygen-ion conducting oxide, such as yttria-stabilized zirconia (YSZ), which exhibits an ionic conductivity of 10−3–10−2 S cm−1 at 700 °C. Although YSZ-based SOFCs are being commercialized, YSZ-Ni anodes are still suffering from carbon deposition (coking) and sulfur poisoning, ensuing performance degradation. Furthermore, the high operating temperatures (>700 °C) also pose challenges to the system compatibility, leading to poor long-term durability. To reduce operating temperatures of SOFCs, intermediate-temperature proton-conducting SOFCs (P-SOFCs) are being developed as alternatives, which give rise to superior power densities, coking and sulfur tolerance, and durability. Due to these advances, there are growing efforts to implement proton-conducting oxides to improve durability of direct-hydrocarbon SOFCs. However, so far, there is no review article that focuses on direct-hydrocarbon P-SOFCs. This concise review aims to first introduce the fundamentals of direct-hydrocarbon P-SOFCs and unique surface properties of proton-conducting oxides, then summarize the most up-to-date achievements as well as current challenges of P-SOFCs. Finally, strategies to overcome those challenges are suggested to advance the development of direct-hydrocarbon SOFCs.

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