Switching Electric Double Layer Potential by Phase Structure Control for Advanced Oxygen Reduction Reaction of...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Designing efficient electrocatalysts for the oxygen reduction reaction (ORR) is crucial for energy conversion technologies.
• A key challenge lies in optimizing the adsorption and desorption of oxygen intermediates on the catalyst surface.
• Cobalt/N-doped carbon (Cobalt@NC) core-shell structures are promising ORR electrocatalysts.

Purpose of the Study:

• To systematically evaluate and compare the ORR activity of hexagonal close-packed (HCP) and face-centered cubic (FCC) cobalt core-shell Cobalt@NC catalysts.
• To elucidate the underlying electronic structure effects influencing ORR performance using theoretical and experimental methods.

Main Methods:

• Density Functional Theory (DFT) calculations to investigate electronic structure and interfacial polarization.
• Experimental synthesis and characterization of HCP and FCC Cobalt@NC catalysts.
• Electrochemical evaluation of ORR activity and performance in Aluminium-air batteries.

Main Results:

• DFT calculations indicated that HCP Cobalt@NC facilitates easier desorption of oxygen intermediates compared to FCC Cobalt@NC.
• Plasma-engineered HCP Cobalt@NC exhibited significantly enhanced ORR kinetics, with a kinetic current density of 6.24 mA cm⁻² at 0.85 V vs RHE.
• HCP Cobalt@NC outperformed both FCC Cobalt@NC and commercial 20 wt.% Pt/C in ORR activity and Aluminium-air battery performance.

Conclusions:

• The study demonstrates that the crystallographic structure of the cobalt core (HCP vs. FCC) critically impacts the ORR performance of Cobalt@NC catalysts.
• HCP Cobalt@NC shows superior catalytic activity and durability for ORR, attributed to optimized oxygen intermediate desorption.
• These findings highlight HCP Cobalt@NC as a highly promising, cost-effective alternative to platinum-based catalysts for ORR applications.