Nitrogen-carbon materials base on pyrolytic graphene hydrogel for oxygen reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Oxygen reduction reaction (ORR) is crucial for energy conversion technologies.
• Nitrogen-doped carbon materials are promising ORR catalysts.
• Understanding the role of different nitrogen configurations is significant.

Purpose of the Study:

• To synthesize graphene hydrogel-based nitrogen-carbon materials (GH N-C) with tunable nitrogen configurations.
• To investigate the electrocatalytic performance of these materials for ORR.
• To correlate nitrogen content and configuration with catalytic activity.

Main Methods:

• Fabrication of graphene hydrogel (GH) precursor via hydrothermal treatment of graphene oxide (GO).
• Calcination of GH in an ammonia atmosphere at varying temperatures to create N-doped graphitic materials.
• Electrochemical characterization of synthesized GH N-C materials for ORR performance.

Main Results:

• GH N-C materials with controllable nitrogen configurations were successfully synthesized.
• GH N-C-900, pyrolyzed at 900°C, demonstrated superior ORR electrocatalytic performance (onset potential: 0.947 V, half-wave potential: 0.830 V).
• High electron transfer number (3.61-3.99), methanol tolerance, and long-term stability were observed.
• A positive correlation was found between pyrrolic-N and quaternary-N content and ORR catalytic activity.

Conclusions:

• The 3D graphene hydrogel structure, defects, and optimized nitrogen doping contribute to excellent ORR performance.
• Pyrrolic-N and quaternary-N are key active sites for ORR catalysis in these materials.
• This study provides insights into designing efficient nitrogen-doped carbon catalysts for energy applications.