Theoretical insights on the exsolved behavior of ruthenium atom in titanate perovskite

Understanding the formation of active nanoparticles at the surface of perovskite oxide supports is vital to improving the electrochemical properties of catalysts. Surface-modified titanates via exsolution have shown great potential applications in energy conversion and storage devices. However, the details of exsolution are unclear, especially at the atomic level. In this work, we use the framework of density-functional theory (DFT) to investigate the exsolved mechanism of Ru atoms on novel SrTiO₃-based perovskite, Sr_0.975Y_0.125Ti_0.95Ru_0.05O_3-δ (SYTR). It is found that the segregation energy of Ru from bulk to surface turns from positive to negative by partially substituting A-site strontium with yttrium. The formation of oxygen vacancy accelerates the dynamic process of exsolution. Ru nanoparticles nucleate preferentially around the vicinity of yttrium sites based on the analysis of the transition states of Ru adatoms. A lower activation energy migration path of Ru could be obtained due to the introduction of A-site deficiency and surface oxygen vacancies simultaneously. The results demonstrate in this work provide significant insights to understand the mechanism of exsolution behavior in titanate perovskites.