New materials prepared in absence of Co and Sr for solid oxide fuel cells and electrolizers

MAGALHAES E SILVA, GABRIEL; ABUIN, GRACIELA; LARRALDE, ANA LAURA

Buenos Aires

Simposio; 8th Symposium on Hydrogen, Fuel Cells and Advanced Batteries; 2022

CNEA

 In the past decades, many researchers studied about new forms of energy to replace the use of fossil fuels which are responsible for serious environmental issues due to their emissions of greenhouse gases. In this context, hydrogen has been considered the ?fuel of the future? given its high energetic value and zero-emission combustion. One of the most promising options in terms of the efficiency of conversion devices based on hydrogen is associated with the Solid Oxide Fuel Cells (SOFCs) and their reversible mode: the Solid Oxide Electrolysis Cells (SOECs). These cells can work simultaneously in the so-called Reversible Solid Oxide Cells (ReSOCs): depending on the cell polarization, devices might work as SOFC to oxidize fuels (as H2) generating electricity; or as a SOEC reducing reactive species (such as H2O) consuming electric energy and producing H2. The main characteristic of these cells is that their main components, both electrodes and the electrolyte, are solid oxides.        The crystalline structure of perovskite oxides, of general formula ABO3, is incredible flexible and can accommodate oxygen vacancies generated by cation substitution in the A and/or B sites. The hopping of these oxygen vacancies give rise to the ionic conduction within the material. Oxygen deficient ABO3-𝛿 perovskites belong to the so-called group of mixed ionic-electronic conductors (MIECs) which are materials presenting both ionic and electronic conduction, and have shown high electrocatalytic activity. Perovskite oxides have played a vital role in the field of energy conversion and storage. Intermediate temperature SOFCs (IT-SOFCs) can operate in the temperature range of 500-800°C unlike conventional SOFCs which operate at high temperatures (800-1000°C). The most studied MIECs are the cobalt oxides but they have a drawback regarding high thermal expansion coefficient, low stability and high toxicity and cost of the Co [1]. The strontium has also been widely used in prototypes. Nevertheless, the latest publications indicate that this element tends to diffuse towards the surface of the materials, promoting their degradation. The mentioned findings allow new research regarding the design of efficient and atoxic materials for their use in SOCs. In this work, we synthetize and characterize ( X-ray diffraction, XRD) a series of CaFeO3 - based perovskites containing Ba and Ni in the A-site and B-site, respectively. The materials investigated are: the parent compound, CaFeO3 (CFO);  Ca0.50(Ba0.50)FeO3- 𝛿 (CBFO) and Ca0.50(Ba0.50)Fe0.50(Ni0.50)O3- 𝛿 (CBFNO).