Intermetallic PtFe Electrocatalysts for the Oxygen Reduction Reaction: Ordering Degree-Dependent Performance.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Atomically ordered platinum-based intermetallic compounds offer advantages over disordered alloys for oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells.
• The influence of the ordering degree in intermetallic catalysts on ORR performance has been largely overlooked due to challenges in synthesis and control.

Purpose of the Study:

• To synthesize and characterize a series of intermetallic platinum-iron (PtFe) catalysts with controlled, varied ordering degrees.
• To investigate the correlation between the ordering degree of PtFe catalysts and their activity and durability for the oxygen reduction reaction (ORR).

Main Methods:

• Preparation of intermetallic PtFe catalysts with particle sizes of 3-4 nm and ordering degrees ranging from 10% to 70%.
• Fabrication of PtFe/Pt core/shell structures with a platinum skin of approximately 3 atomic layers.
• Electrochemical testing of catalysts in H2-O2 fuel cells to evaluate ORR activity and durability.

Main Results:

• A positive correlation was observed between the ordering degree of intermetallic PtFe catalysts and their ORR activity and durability.
• The highly ordered PtFe/Pt catalyst achieved a mass activity of 0.92 A mgPt−1 at 0.9 V (iR-corrected) with only 24% activity loss after accelerated durability tests.
• Performance enhancement is attributed to the compressive strain effect from the intermetallic PtFe core and the inherent stability of the ordered structure.

Conclusions:

• The ordering degree is a critical parameter for optimizing the performance of intermetallic PtFe catalysts in proton-exchange-membrane fuel cells.
• Highly ordered intermetallic PtFe catalysts offer superior activity and durability for the oxygen reduction reaction.
• Controlled synthesis of ordered intermetallic structures is crucial for advancing fuel cell technology.