Stable Cobalt Nanoparticles and Their Monolayer Array as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient and stable electrocatalysts is crucial for water splitting technologies.
• Noble metal catalysts like iridium are effective but expensive and scarce.
• Cobalt nanoparticles (NPs) are explored as a cost-effective alternative.

Purpose of the Study:

• To synthesize and stabilize monodisperse cobalt nanoparticles (NPs).
• To evaluate the electrocatalytic activity and stability of Co NPs for the oxygen evolution reaction (OER).
• To investigate the intrinsic OER activity of Co NPs using a monolayer array.

Main Methods:

• Synthesis of monodisperse cobalt nanoparticles.
• Stabilization via reductive annealing at 600 °C.
• Electrocatalytic testing in 0.1 M KOH, including monolayer array assembly.

Main Results:

• Stable Co NPs exhibit high OER activity (10 mA/cm² at 0.39 V overpotential) and superior stability compared to commercial Ir catalysts.
• Co NPs in a monolayer array demonstrate significantly enhanced turnover frequency (2.13 s⁻¹) and mass activity (1949 A/g) at 0.4 V overpotential.
• Monolayer array of Co NPs shows 15 times higher activity than NPs on carbon black.

Conclusions:

• Stabilized cobalt nanoparticles are highly active and stable noble-metal-free OER electrocatalysts.
• Monolayer assembly provides a platform for studying intrinsic catalytic properties and achieving superior performance.
• These Co NPs represent a promising alternative for efficient and sustainable water splitting.