Understanding the Structural Evolution of IrFeCoNiCu High-Entropy Alloy Nanoparticles under the Acidic Oxygen...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• High-entropy alloy (HEA) nanoparticles are emerging as potent catalysts for the oxygen evolution reaction (OER).
• Acidic OER catalysts are crucial for energy conversion technologies but often face stability challenges.

Purpose of the Study:

• To synthesize and evaluate the performance of IrFeCoNiCu-HEA nanoparticles as electrocatalysts for the acidic OER.
• To investigate the structural evolution and active site formation of HEA nanoparticles under OER conditions.

Main Methods:

• Microwave-assisted shock synthesis was employed to prepare IrFeCoNiCu-HEA nanoparticles on a carbon paper substrate.
• Electrochemical characterization, including OER activity and stability testing in 0.1 M HClO₄, was performed.
• In-situ/operando analysis was used to study the surface structure evolution during electrochemical activation.

Main Results:

• The IrFeCoNiCu-HEA nanoparticles exhibited excellent OER activity, with an overpotential of ~302 mV at 10 mA cm^-2.
• The HEA catalyst demonstrated improved stability over 12 hours of operation compared to monometallic Ir.
• An active, Ir-rich shell layer with nanodomain features formed on the HEA surface due to 3d metal dissolution, while the core maintained its single-phase HEA structure.

Conclusions:

• IrFeCoNiCu-HEA nanoparticles are highly effective electrocatalysts for the acidic OER, offering superior activity and stability.
• The formation of a dynamic, Ir-rich surface layer is key to the enhanced catalytic performance.
• This study highlights the tunable near-surface structural dynamics of HEA nanoparticles under acidic operating conditions.