An Ultrasmall Ordered High-Entropy Intermetallic with Multiple Active Sites for the Oxygen Reduction Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Controlling atomic-level multimetallic ensembles, especially in high-entropy alloys (HEAs) with over five elements, presents significant challenges.
• Developing efficient electrocatalysts is crucial for advancing clean energy technologies like fuel cells.

Purpose of the Study:

• To synthesize and characterize an ultrasmall, well-ordered high-entropy intermetallic (HEI) nanoparticle catalyst.
• To evaluate the electrocatalytic performance of the novel catalyst for the oxygen reduction reaction (ORR).
• To explore the potential of HEIs in proton exchange membrane fuel cells (PEMFCs).

Main Methods:

• Utilized a space-confined strategy for synthesizing ultrasmall (∼2 nm) PtFeCoNiCuZn high-entropy intermetallic (PFCNCZ-HEI) nanoparticles.
• Assessed the ORR activity of PFCNCZ-HEI via electrochemical measurements.
• Assembled a PEMFC using PFCNCZ-HEI as the cathode catalyst and evaluated its performance.
• Performed theoretical calculations to understand the electronic structure and active sites.

Main Results:

• Achieved an ultrahigh mass activity of 2.403 A mg_Pt^-1 at 0.90 V vs RHE for the ORR, 19-fold higher than commercial Pt/C.
• Demonstrated a PEMFC with a power density of 1.4 W cm^-2 and a mass-normalized rated power of 45 W mg_Pt^-1.
• Theoretical calculations indicated modulated outer electrons on non-noble metal atoms, creating multiple active centers.

Conclusions:

• The developed PFCNCZ-HEI nanoparticles exhibit exceptional electrocatalytic activity for the ORR.
• The space-confined synthesis strategy is effective for creating highly ordered HEI nanoparticles.
• This work provides a promising catalyst design for highly ordered HEI nanoparticles in electrocatalysis.