Doping on the crystal structure is a common strategy
to modify
electronic conductivity, ion conductivity, and thermal stability.
In this work, a series of transition metal elements (Fe, Co, Cu, Ru,
Rh, Pd, Os, Ir, and Pt) doped at the Ni site of La2NiO4+δ compounds as cathode materials of solid oxide fuel
cells (SOFCs) are explored based on first-principles calculations,
through which the determinant factors for interstitial oxygen formations
and migrations are discussed at an atomistic level. The interstitial
oxygen formation and migration energies for doped La2NiO4 are largely reduced in contrast to the pristine La2NiO4+δ, which is explained by charge density distributions,
charge density gradients, and Bader charge differences. In addition,
based on a negative correlation between formation energy and migration
barrier, the promising cathode materials for SOFCs were screened out
between the doped systems. The Fe-doped structures of x = 0.25, Ru-doped structures of x = 0.25 and x = 0.375, Rh-doped structures of x = 0.50,
and Pd-doped structures of x = 0.375 and x = 0.50 are screened out with interstitial oxygen formation
energy less than −3 eV and migration barrier less than 1.1
eV. In addition, DOS analysis indicates that doping to La2NiO4+δ also facilitates the electron conductions.
Our work provides a theoretical guideline for the optimization and
design of La2NiO4+δ-based cathode materials
by doping.