Controlling surface cation segregation in a nanostructured double perovskite GdBaCo₂O_5+δ electrode for solid oxide fuel cells

Abstract

Mechanistic studies, utilizing molecular dynamics (MD) and density functional theory (DFT) calculations, were undertaken to provide a molecular level explanation of Ba cation segregation in double perovskite GdBaCo2O5+δ (GBCO) electrodes.

Synergistic Interaction of Double/Simple Perovskite Heterostructure for Efficient Hydrogen Evolution Reaction at High Current Density

“…Although the overlap between Co 2p and Ba 3d main peaks makes it difficult to accurately identify the surface Co valence, as the chemical shift between Co 2p/Ba 3d is only around 0.3–0.4 eV, two strong lines locating at ≈779.5 and ≈795 eV indicate that the main oxidation state of Co ions in the perovskite samples is 3+. [ 27a,28 ] The apparent shoulder peaks at 777.4 and 792.6 eV in PBC and PB 0.94 C are ascribed to the Ba–O interrelation, evidence for the structural stress from oxygen nonstoichiometry and A‐site deficiency. [ 9,29 ] The intensity of interrelation peaks becomes weaker for PB 0.94 C‐DSPH after the separation of simple perovskite because double/simple perovskite phases revert to more stable structures.…”

Surface restructuring of a perovskite-type air electrode for reversible protonic ceramic electrochemical cells

“…The smaller the segregation energy, the easier the segregation of the B cation from the bulk to the surface. The bulk diffusion properties 80 , 81 were examined using the climbing-image nudged elastic band (CI-NEB) method 82 . The higher oxygen vacancy energy of A-cation deficient Ba 0.9 (Co 0.63 Fe 0.25 Nb 0.13 )O 3.0 than Ba(Co 0.63 Fe 0.25 Nb 0.13 )O 3.0 (2.95 eV versus 1.87 eV, Supplementary Table 6 ) leads to a slightly higher diffusion migration barrier (0.60 eV versus 0.58 eV, Supplementary Fig.…”

Recent advances, practical challenges, and perspectives of intermediate temperature solid oxide fuel cell cathodes

“…A concern with A′-site alkaline earth cations, particularly Sr and Ba, is their preferential segregation towards the cathode surface 198–202 and their chemical instability in CO 2 as they have a high tendency to form carbonates on reaction with atmospheric CO 2 . 41–43 The challenge this phenomenon presents is that surface enriched strontium and barium oxides are susceptible to reaction with other gaseous contaminants such as Cr and CO 2 to form secondary phases on the electrode surface which are electronically insulating and impede surface oxygen exchange, consequently hampering the conductivity and electrochemical performance of the cathodes.…”

“…After ∼50 h of operation, the PBCC cathode showed stable power output with a degradation rate ∼1/24 of that of state-of-the-art LSCF cathode under the same operating conditions, indicating good tolerance to CO 2 . Anjum et al 199 observed a substantial reduction in Ba surface segregation in nanostructured GdBaCo 2 O 5+ δ (GBCO) (∼10 nm radius) as well as reduced impedance in comparison with the chemically synthesised bulk sized GBCO electrode. Thus, they proposed applying nano-structuring strategies to control surface cation segregation.…”