Ab initio study of Pr1-xSrxCrO3-δ cubic perovskites: Solid oxide fuel cells applications

Abstract

Perovskite-type materials have been proposed to produce solid oxide fuel cells (SOFCs). The cathode is one layer that makes up the SOFCs, and figure as important player in order to catalyze the reduction of O2. As of the Density Functional Theory, this work presents a theorical study of oxygen vacancy (VO) effects on perovskites Pr1-xSrxCrO3-δ (x ​= ​0, 0.25 and 1; δ ​= ​0.042), in oxygen-poor and oxygen-rich growth atmospheres, for several charge states (VOq). Oxygen vacancy has a fundamental role to optimize the catalysis process in SOFCs cathode. From the formation energy (Ef) calculation, VO+1 is the most stable state in metallic SrCrO2.958, which indicates its donor character. For PrCrO2.958, oxygen vacancy is a negative-U center, with transition energy between charge states (VO2+/VO0) at 0.38 ​eV above valence band top. Among the three distinct structures of Pr0.75Sr0.25CrO2.958, namely, C1, C2 and C3, VO1− is energetically most favorable in C3, which gives its acceptor character. Relative to other systems, SrCrO2.958 has the lowest VO formation energy. Through magnetic moment study, oxidation states of chromium are Cr4+ (d2) in SrCrO3-δ, and Cr3+ (d3) in PrCrO3-δ and Pr0.75Sr0.25CrO3-δ. Furthermore, praseodymium Pr3+ (f2) is present in PrCrO3-δ and Pr0.75Sr0.25CrO3-δ.