Development of double-perovskite compounds as cathode materials for low-temperature solid oxide fuel cells

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Double-perovskite oxides are promising for oxygen reduction reactions due to fast oxygen ion diffusion and catalytic activity.
• NdBaCo2O(5+δ) (NBCO) exhibits good performance but requires enhanced stability, particularly in CO2-containing atmospheres.

Purpose of the Study:

• To investigate the effect of calcium (Ca) doping on the stability and electrochemical performance of NdBaCo2O(5+δ) (NBCO).
• To explore the underlying mechanisms for enhanced stability in Ca-doped NBCO (NBCaCO).

Main Methods:

• Synthesis and characterization of NdBa(1-x)Ca(x)Co2O(5+δ) (NBCaCO) compounds.
• Electrochemical performance testing under various atmospheric conditions.
• Density functional theory (DFT) calculations to determine electron affinity.
• Coulometric titration to assess redox stability.

Main Results:

• Ca doping into the A-site of NBCO significantly enhances stability in both air and CO2-rich environments.
• NBCaCO demonstrates excellent electrochemical performance, indicating improved oxygen reduction reaction kinetics.
• DFT calculations revealed increased electron affinity for mobile oxygen species due to Ca doping.
• Coulometric titration confirmed enhanced redox stability in the Ca-doped compounds.

Conclusions:

• Partial substitution of Ba with Ca in NdBaCo2O(5+δ) leads to a class of highly stable and electrochemically active double-perovskite materials.
• The enhanced stability is attributed to improved electronic structure and redox properties conferred by Ca doping.
• NBCaCO represents a significant advancement for durable and efficient oxygen electrode materials in electrochemical devices.