Spin-State Tuning in PrFeO_3-δ Perovskite for High-Temperature Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Perovskite oxides are crucial for electrocatalytic applications.
• Understanding the link between electronic structure and oxygen evolution reaction (OER) in solid oxide electrolysis cells (SOECs) is vital but underexplored.
• The role of e_g electron occupancy in high-temperature OER performance needs further investigation.

Purpose of the Study:

• To investigate the effect of A-site doping on the OER performance of perovskite oxides.
• To explore the relationship between B-site Fe electronic structure and high-temperature OER in SOECs.
• To guide the rational design of Fe-based perovskites for SOEC anode applications.

Main Methods:

• Synthesis of A-site doped Pr_0.5Ae_0.5FeO_3-δ (Ae = Ca, Sr, Ba) perovskite oxides.
• Electrocatalytic testing for high-temperature oxygen evolution reaction (OER) in SOECs.
• Characterization using X-ray absorption spectroscopy, ⁵⁷Fe Mössbauer spectroscopy, and magnetic susceptibility measurements.

Main Results:

• Pr_0.5Ae_0.5FeO_3-δ perovskites exhibit exceptional high-temperature OER performance.
• Pr_0.5Ba_0.5FeO_3-δ achieved a current density of 3.33 A cm^-2 at 2.0 V and 800 °C.
• Doping induced a spin-state transition of Fe from high-spin Fe³⁺ to low-spin Fe⁴⁺, reducing e_g occupancy.

Conclusions:

• Reduced e_g electron occupancy in B-site Fe is critical for high-temperature OER performance in SOECs.
• The spin-state transition of Fe accelerates charge transfer and oxygen transport.
• Fe-based perovskites with tailored electronic structures are promising SOEC anode materials.