Concave Grain Boundaries Stabilized by Boron Segregation for Efficient and Durable Oxygen Reduction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The oxygen reduction reaction (ORR) is crucial for fuel cells and metal-air batteries but is kinetically limited, even with platinum (Pt) catalysts.
• Reducing platinum usage requires enhancing both the specific activity and electrochemically active surface area (ECSA) of Pt catalysts.

Purpose of the Study:

• To develop efficient ORR catalysts by creating ultrafine, grain boundary (GB)-rich Pt nanoparticle assemblies.
• To improve the specific activity and ECSA of Pt catalysts for enhanced ORR performance.

Main Methods:

• Synthesized ultrafine Pt nanoparticle assemblies with a high density of grain boundaries.
• Utilized boron segregation to stabilize the grain boundaries and active sites.
• Characterized the ORR performance using electrochemical techniques, measuring specific and mass activities.

Main Results:

• The grain boundary-rich Pt nanoassemblies exhibited a significantly large ECSA and high density of active sites.
• Boron-stabilized Pt nanoassemblies achieved ORR specific activity of 9.18 mA cm^-2 and mass activity of 6.40 A mg^-1 _Pt at 0.9 V vs. RHE.
• The developed catalysts demonstrated over 35-fold improvement compared to commercial Pt/C catalysts with minimal degradation after 60,000 cycles.

Conclusions:

• Ultrafine, GB-rich Pt nanoparticle assemblies are highly effective ORR catalysts.
• Boron stabilization enhances catalytic activity and durability by preserving active sites.
• This approach provides a versatile platform for optimizing nanoparticle catalysts for various applications.