Acidic oxygen reduction by single-atom Fe catalysts on curved supports

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing cost-effective electrocatalysts for proton-exchange membrane fuel cells (PEMFCs) is crucial.
• Platinum group metal catalysts are effective but expensive.
• Existing iron-nitrogen-carbon (Fe/N-C) catalysts face challenges in activity and durability due to intermediate adsorption and Fenton reactions.

Purpose of the Study:

• To design and develop a novel Fe/N-C electrocatalyst with enhanced activity and durability for PEMFCs.
• To address the limitations of current Fe/N-C catalysts, specifically strong intermediate binding and Fe demetallization.
• To achieve high performance in platinum-group-metal-free PEMFCs.

Main Methods:

• Synthesis of a new Fe/N-C catalyst featuring nanoprotrusions on 2D carbon layers.
• Embedding single Fe-atom sites within the inner curved surface of nanoprotrusions.
• Utilizing a graphitized outer carbon layer on nanoprotrusions to modify intermediate binding and radical production.

Main Results:

• The novel Fe/N-C catalyst exhibits a unique nanostructure with dispersed nanoprotrusions.
• Single Fe-atom sites are primarily anchored within the nanoprotrusions' inner curved surfaces.
• The graphitized outer carbon layer effectively weakens oxygenated intermediate binding and reduces hydroxyl radical generation.
• Achieved a record power density of 0.75 W cm⁻² in a H₂-air PEMFC.
• Demonstrated 86% activity retention after over 300 hours of operation.

Conclusions:

• The designed Fe/N-C catalyst represents a significant advancement in platinum-group-metal-free electrocatalysts.
• The nanostructure and Fe-atom site integration effectively enhance catalytic performance and durability.
• This development paves the way for more cost-effective and high-performing fuel cells.