Surface-engineered cobalt nitride composite as efficient bifunctional oxygen electrocatalyst.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Rechargeable metal-air batteries require efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).
• Developing low-cost, high-performance electrocatalysts is crucial for practical applications.

Purpose of the Study:

• To synthesize and characterize a novel cobalt nitride hybrid bifunctional electrocatalyst.
• To investigate its catalytic activity and stability for ORR and OER.
• To elucidate the origin of its catalytic performance through theoretical calculations.

Main Methods:

• Synthesis of sulfur-doped and mildly oxidized Co5.47N nanoparticles on nitrogen-doped reduced graphene oxide (O-S-Co5.47N@N-RGO).
• Electrochemical characterization of ORR and OER performance in 0.1 M KOH.
• Density functional theory (DFT) calculations to understand active sites.

Main Results:

• The O-S-Co5.47N@N-RGO composite demonstrated excellent bifunctional catalytic activity.
• Achieved an ORR half-wave potential of 0.82 V and an OER over-potential of 380 mV at 10 mA cm⁻².
• DFT calculations suggest Co-N4 sites for ORR and surface Co sites for OER.

Conclusions:

• The developed O-S-Co5.47N@N-RGO is a highly efficient and stable bifunctional electrocatalyst.
• The study provides insights into the active sites, advancing the design of oxygen electrocatalysts.
• This work contributes to the development of advanced rechargeable metal-air batteries.