Changing your tune on catalytic efficiency: Tuning Cr concentration in La0.3Sr0.7Fe1-xCrxO3-δ perovskite as a cathode in solid oxide electrolysis cell

• Published in: Computational materials science Vol. 210; p. 111462
• Main Authors: Fidelsky Kozokaro, Vicky, Biswas, Santu, Caspary Toroker, Maytal
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2022
• Subjects: Catalysis; Computational materials science; Density functional theory; Fuel cells; Density functional theory; Catalysis; Fuel cells; Computational materials science
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2022.111462

[Display omitted] Solid Oxide Electrolysis Cell (SOEC) are in the focus of interest for many years, due to their ability to convert CO2 emissions to CO fuel, and thus, regenerate fuels and diminish environmental pollution. A perovskite structure (ABO3) electrode La0.3Sr0.7Fe1-xCrxO3-δ (LSFCr, A = La, Sr, B = Fe, Cr) with x = 0, 0.1, 0.2 and 0.3, was found to be a proper candidate for SOEC performance, and was tested experimentally for various properties under various environments. It has been showed that the optimal trade-off is present when x = 0.3 (La0.3Sr0.7Fe0.7Cr0.3O3-δ) and the SrCrO4 phase was found when x > 0.33. It was also reported that Cr dopants can improve the structural stability of La0.3Sr0.7FeO3-δ in reducing atmospheres. The current work investigates by the density functional theory (DFT) method the effect of Cr stoichiometry on La0.3Sr0.7Fe1-xCrxO3-δ perovskite on the electronic properties, mechanical properties, and surface catalytic activity of CO2 reduction. This work is based on our previous experimental and DFT+U study that revealed that surface models with two surface oxygen vacancies are necessary for describing CO2 reduction. Here the calculations showed that Cr atoms have an impact on the electronic behavior of LSFCr, since the bandgap depends on Cr concentration. According to the bulk modulus values, La0.3Sr0.7Fe1-xCrxO3-δ perovskite may be mechanically stable under applied stress. Moreover, the mechanical bulk modulus lowering, when SrCrO4 is present, may be an indication of possible lower stability and degradation. The calculations showed that more Cr atoms near the active site “changes your tune” on CO2 reduction by improving the reaction thermodynamically through dictating the reducing and oxidizing roles to the participating atoms in the catalysis. The low +3 oxidation state of Cr has an impact on reaction progress by creating more reductive environment.