Carbon Defect-Induced Reversible Carbon-Oxygen Interfaces for Efficient Oxygen Reduction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing metal-free electrocatalysts for the oxygen reduction reaction (ORR) is crucial for fuel cell applications, especially in acidic media.
• Existing catalysts often struggle with performance and stability in acidic environments.

Purpose of the Study:

• To fabricate a novel metal-free carbon material (C-900) for efficient oxygen reduction reaction (ORR) catalysis.
• To evaluate the performance of C-900 as a cathode catalyst in air-breathing fuel cells.

Main Methods:

• Fabrication of C-900 using a self-sacrificed template and solid-state reaction strategy.
• Performance evaluation in alkaline and acidic media, compared to 20% Pt/C.
• Oxygen temperature-programmed desorption (O2-TPD) to study O2 chemisorption.
• Synchrotron radiation-based X-ray absorption spectroscopy (XAS) to confirm defect sites.

Main Results:

• C-900 exhibits superior performance to 20% Pt/C in alkaline media and comparable performance in acidic conditions.
• C-900 demonstrates high performance (1160 W L-1) and excellent stability as a cathode catalyst in air-breathing fuel cells.
• Oxygen temperature-programmed desorption revealed strong selective chemisorption of O2 on C-900.
• Abundant carbon defect sites in C-900 were confirmed by XAS, correlating with enhanced O2 chemisorption.

Conclusions:

• The metal-free C-900 material shows promising potential as an ORR electrocatalyst for fuel cells.
• Abundant defect sites and strong O2 chemisorption contribute to the excellent ORR activity of C-900.
• The reversible carbon-oxygen interface induced by defect sites is key to the catalyst's high performance.