Computational study of native defects and oxygen diffusion in the YTiO3±δ as cathode materials in SOFCs

NR Martins and DD Borges and PD Borges, JOURNAL OF SOLID STATE CHEMISTRY, 325, 124142 (2023).

DOI: 10.1016/j.jssc.2023.124142

Solid oxide fuel cells (SOFCs) are a promising technology to produce efficient and sustainable electrical energy as an alternative to those generated by fossil fuels. The perovskites-based ceramics are a viable option for building the cathode of these devices since they have a relatively low cost and remarkable efficiency regarding transport properties. Indeed, perovskites in the presence of dopants or native defects such as oxygen vacancy (VO) play a fundamental role in optimizing the catalysis process of oxygen reduction reaction and enhancing the oxygen ion product diffusion into the cathode of SOFCs. Another native defect found in the perovskites is the interstitial oxygen (Oi) and despite being very common, there are few studies on the effects of this kind of defect on the cathode activities. Based on the Density Functional Theory (DFT) and classical Molecular Dynamics simulations (MD), this work presents a theoretical study of the effects of VO and Oi in YTiO3 & PLUSMN;8 perovskites. It was observed that the presence of VO and Oi does not significantly change the structural characteristics of the YTiO3 & PLUSMN;8. The linear coefficient of thermal expansion (CTE) and the mechanical properties of pristine and defective structures presented satisfactory results and compatibility as compared with the main electrolytes used in SOFCs. From the calculation of the formation energy, Oi  2 is the most stable state in YTiO3. Finally, our findings show a high oxygen self-diffusion coefficient and low activation energy when VO or Oi defects are considered, making the YTiO3 & PLUSMN;8 a competitive material when compared to other perovskites.

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