Characterization of the Structural and Electrochemical Properties of Praseodymium Oxide as an Efficient Oxygen Electrode for Intermediate Solid Oxide Cells
Authors: Lemieszek Bartłomiej , Molin Sebastian , Jasiński Piotr 
Published: December 2024

Solid oxide cells are a promising, potentially zero-emission energy source that can play a significant role in the future of the world's energy industry. A classical solid oxide cell (SOC) consists of a cathode, an anode, and an electrolyte. The cathode (oxygen electrode in fuel mode) is responsible for the catalytic reduction of oxygen. Obtaining a functional oxygen electrode with adequate performance is one of the key challenges that is still unresolved. Especially since the general trend in this field indicates obtaining efficient cells at temperatures as low as 600°C and even 500°C. Lowering the operating temperature of the cell is associated with lowering the costs of this technology; this is a crucial factor for the fast commercialization of the technology. One of the main phenomena that needs to be solved is the high polarization resistance of the cathode. This is an important factor because the polarization resistance on this electrode constitutes the vast majority of the entire cell. There is a need for new cathode materials that will have better parameters than currently known materials such as LSC or LSCF, which are already state-of-the-art [1]. One of the promising materials with potential use in SOC is praseodymium oxide [2, 3]. This compound has a very good affinity for oxygen while exhibiting low electrode conductivity. Moreover, it is highly variable and, due to its relatively new status as an oxygen electrode material, is still unknown.

The present work shows the result of the research on a high-performance oxygen electrode composed of praseodymium oxide for intermediate-temperature SOCs. Praseodymium oxide is a complex compound with properties that need to be better understood. There is a limited number of articles in the literature referring to praseodymium oxide as a potential oxygen electrode. The material shows several transformations in different temperature ranges. Simultaneously, it is among the most promising, cobalt-free, new-generation materials employed in SOCs.

The spin-coating method applied the oxygen electrode to CGO (Ce0.8Gd0.2O2-d) as a typical barrier layer. The material was analysed by XRD, HT-XRD, HT-Raman spectroscopy to determine the structural parameters in a range of 400 °C – 1000 °C. The conductivity parameters was determined by Van der Pauw method. The electrochemical properties of this oxygen electrode material were determined using electrochemical impedance spectroscopy. For this purpose, a series of symmetrical samples were prepared. The thickness of the cathode has been optimised. Annealing temperature's impact was investigated, and at 600 °C, a polarisation resistance of 24 mΩ cm-2 was achieved. Detailed studies were conducted on various pO2 values to identify the electrode processes. The experiments, supported by DRT analysis, demonstrated the electrode processes and their efficiency. Stability experiments were conducted to demonstrate the oxygen electrode stability during operation. Additional impedance tests in a wet air atmosphere were performed to determine stability. The last step of experiment was a fuel cells, with proposed oxygen electrode material, characterized in long time period.

Acknowledgements

This research has been supported by National Science Centre (NCN) DAINA 2 project number UMO-2020/38/L/ST8/00513: “Porous metal supported micro-scale solid oxide fuel cells: fundamentals, fabrication and testing”.

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