Highly stable and active catalyst in fuel cells through surface atomic ordering.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Shape-controlled alloy nanoparticle catalysts show promise for oxygen reduction reaction (ORR) in liquid half-cells.
• Challenges exist in translating this success to membrane electrode assembly (MEA) catalyst layers due to demanding fuel cell conditions, requiring a balance between durability and activity.

Purpose of the Study:

• To develop a strategy for enhancing the stability and activity of shape-controlled platinum-iron alloy catalysts in fuel cell MEAs.
• To enable selective surface transformation into ordered intermetallic structures via atomic ordering at low temperatures.

Main Methods:

• A novel strategy was employed to limit atomic diffusion within surface layers, promoting phase transition and shape retention during thermal treatment.
• Low-temperature thermal treatment facilitated the selective transformation of platinum-iron nanowire surfaces into intermetallic structures through atomic ordering.
• Density functional calculations were used to investigate the mechanisms of surface stabilization and ORR activity enhancement.

Main Results:

• The developed catalysts demonstrated enhanced stability in MEAs with a 50% reduction in iron loss.
• High catalytic activity comparable to that observed in liquid half-cells was maintained.
• Density functional calculations indicated that the ordered intermetallic surface enhances morphological stability against corrosion and boosts ORR activity.

Conclusions:

• Surface engineering via atomic ordering is an effective strategy for stabilizing shape-controlled platinum-based alloy catalysts in fuel cells.
• This approach offers potential for practical applications, improving durability and maintaining activity in demanding fuel cell environments.