Composite Bifunctional Electrocatalyst for the Oxygen Reduction and Evolution Reactions

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Bifunctional electrocatalysts are essential for efficient energy conversion devices like fuel cells and electrolyzers.
• These catalysts must exhibit high activity for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR).
• Stability under a wide potential range and alternating redox conditions is a critical challenge.

Purpose of the Study:

• To rigorously test a composite Ni_0.95Fe_0.05O_1±δ/NiCo₂O₄ as a bifunctional catalyst for anion exchange membrane (AEM) fuel cell and electrolyzer applications.
• To evaluate the catalyst's performance and stability under alternating potential conditions.
• To compare catalyst evaluation results from fundamental rotating disk electrode (RDE) methods with those from AEM single-cell testing.

Main Methods:

• Synthesis and characterization of the composite Ni_0.95Fe_0.05O_1±δ/NiCo₂O₄ catalyst.
• Electrochemical testing using rotating disk electrode (RDE) methodology.
• Anion exchange membrane (AEM) single-cell testing under simulated fuel cell and electrolyzer operation.
• Alternating potential stability tests to mimic device cycling.

Main Results:

• The bifunctional catalyst maintained good oxygen evolution reaction (OER) activity even after harsh stability testing.
• Significant deterioration in oxygen reduction reaction (ORR) activity was observed under the same conditions.
• Discrepancies between RDE and single-cell test results highlight the importance of evaluating catalysts under realistic operating conditions.

Conclusions:

• The composite Ni_0.95Fe_0.05O_1±δ/NiCo₂O₄ exhibits promising OER stability but requires improvement in ORR durability for practical bifunctional applications.
• Evaluating electrocatalysts using both fundamental and applied techniques provides a more comprehensive understanding of their performance and limitations.
• This study offers valuable insights for designing next-generation bifunctional electrocatalysts for electrochemical energy systems.