Abstract
Exsolved perovskites can be obtained from lanthanum ferrites, such as La0.6Sr0.4Fe0.8Co0.2O3, as result of Ni doping and thermal treatments. Ni can be simply added to the perovskite by an incipient wetness method. Thermal treatments that favor the exsolution process include calcination in air (e.g., 500 °C) and subsequent reduction in diluted H2 at 800 °C. These processes allow producing a two-phase material consisting of a Ruddlesden–Popper-type structure and a solid oxide solution e.g., α-Fe100-y-zCoyNizOx oxide. The formed electrocatalyst shows sufficient electronic conductivity under reducing environment at the Solid Oxide Fuel Cell (SOFC) anode. Outstanding catalytic properties are observed for the direct oxidation of dry fuels in SOFCs, including H2, methane, syngas, methanol, glycerol, and propane. This anode electrocatalyst can be combined with a full density electrolyte based on Gadolinia-doped ceria or with La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) or BaCe0.9Y0.1O3-δ (BYCO) to form a complete perovskite structure-based cell. Moreover, the exsolved perovskite can be used as a coating layer or catalytic pre-layer of a conventional Ni-YSZ anode. Beside the excellent catalytic activity, this material also shows proper durability and tolerance to sulfur poisoning. Research challenges and future directions are discussed. A new approach combining an exsolved perovskite and an NiCu alloy to further enhance the fuel flexibility of the composite catalyst is also considered. In this review, the preparation methods, physicochemical characteristics, and surface properties of exsoluted fine nanoparticles encapsulated on the metal-depleted perovskite, electrochemical properties for the direct oxidation of dry fuels, and related electrooxidation mechanisms are examined and discussed.
Highlights
Achieving fuel flexibility in fuel cells has been a focus of high-temperature fuel cells since their discovery [1,2]
In this mini-review, we have summarized the properties of these novel anode materials, their performance in Solid Oxide Fuel Cell (SOFC), and the specific reaction mechanisms investigated through a combination of electrochemical experiments and the chromatographic analyses of effluents
As this catalyst was suggested for the electrochemical conversion of organic fuels in SOFCs, preliminary catalytic tests have been carried out to collect information concerning its reliability toward preliminary catalytic tests have been carried out to collect information concerning its reliability the most common reactions occurring in the anode compartment of an SOFC during its operation
Summary
Achieving fuel flexibility in fuel cells has been a focus of high-temperature fuel cells since their discovery [1,2]. A further step forward in tailoring these perovskite materials for the use as an anode in SOFCs is relying on the addition of ceria to increase the oxygen storage capacity and the electronic/ionic percolation The authors of this mini-review have intensively worked on modified and exsolved perovskite for application as an anode in SOFCs for several years demonstrating an effective oxidation of various organic fuels directly fed to the cell [56,57,58,59,60,61,62,63]. The process has been enhanced by tailoring the thermal treatments to consolidate the modified perovskite structure In this mini-review, we have summarized the properties of these novel anode materials, their performance in SOFCs, and the specific reaction mechanisms investigated through a combination of electrochemical experiments and the chromatographic analyses of effluents
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