High-Entropy Co-Based Oxygen Electrodes with Enhanced Thermomechanical Compatibility for Reversible Protonic Ceramic...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Conversion and Storage

Background:

• Reversible protonic ceramic cells (R-PCCs) are crucial for energy conversion and storage.
• Effective oxygen electrodes are vital for R-PCC performance, requiring high catalytic activity for oxygen reduction/evolution reactions (ORR/OER) and compatible thermal expansion coefficients (TEC).

Purpose of the Study:

• To explore novel high-entropy perovskites Pr_0.2Ba_0.2Sr_0.2La_0.2Nd_0.2MeO_3-δ (Me = Co, Fe, Mn) as potential oxygen electrodes for R-PCCs.
• To evaluate the electrochemical performance, thermomechanical compatibility, and stability of these new materials.

Main Methods:

• Synthesis and characterization of high-entropy perovskites.
• Evaluation of TEC and electrochemical performance in fuel cell (FC) and electrolysis (EC) modes.
• Testing of R-PCCs with novel electrodes under various operating conditions (H₂O electrolysis, CO₂-H₂O co-electrolysis, reversible operation).

Main Results:

• Pr_0.2Ba_0.2Sr_0.2La_0.2Nd_0.2CoO_3-δ (PBSLNC) exhibited a TEC of 12.02 × 10^-6 K^-1, compatible with BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3-δ (BCZYYb) electrolyte.
• The R-PCC with PBSLNC achieved a peak power density of 0.87 W cm^-2 (FC mode) and high current densities in H₂O electrolysis (-1.39 A cm^-2 at 650 °C) and CO₂-H₂O co-electrolysis (-1.45 A cm^-2 at 700 °C).
• Exceptional stability was demonstrated: 150 h (FC/EC modes), 96 h (CO₂-H₂O co-electrolysis), and 100 h (reversible mode).

Conclusions:

• Novel high-entropy perovskites, particularly PBSLNC, are effective oxygen electrodes for R-PCCs.
• PBSLNC offers a promising strategy for designing efficient Co-based oxide catalysts with low TEC for advanced R-PCCs.
• This research advances the development of high-performance and stable R-PCCs for energy applications.