Bionic Preparation of CeO₂-Encapsulated Nitrogen Self-Doped Biochars for Highly Efficient Oxygen Reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient and stable electrocatalysts for oxygen reduction reaction (ORR) is crucial for energy conversion technologies.
• Platinum-based catalysts are effective but suffer from high cost and poor methanol tolerance.
• Nitrogen-doped carbon materials offer promising alternatives due to their unique electronic properties.

Purpose of the Study:

• To synthesize and characterize novel carbonaceous materials, CeO₂-encapsulated nitrogen-doped biochars (BC-Ce-X), for ORR.
• To evaluate the ORR performance of BC-Ce-X materials and compare them with commercial Pt/C catalysts.
• To investigate the synergistic effects between CeO₂ and nitrogen-doped biochar for enhanced ORR activity.

Main Methods:

• Biomimetic preparation of biomass precursor in a Ce-enriched solution.
• Hydrothermal treatment and pyrolysis to synthesize CeO₂-encapsulated nitrogen-doped biochars (BC-Ce-X).
• Electrochemical characterization (ORR, Zn/air batteries) and density functional theoretical (DFT) calculations.

Main Results:

• BC-Ce-X materials exhibited high specific surface areas (up to 566 m²/g) with embedded CeO₂ nanoparticles containing abundant oxygen vacancies.
• BC-Ce-X demonstrated superior ORR performance with onset potentials of ~0.90-0.91 V, surpassing commercial Pt/C and cerium-free biochar (BC).
• BC-Ce-2 showed enhanced methanol tolerance and stability compared to Pt/C, and excellent electrochemical activity for Zn/air batteries.

Conclusions:

• CeO₂-encapsulated nitrogen-doped biochars are highly effective ORR electrocatalysts.
• The synergistic interaction between pyri-N/C sites and CeO₂ with oxygen vacancies significantly boosts ORR performance.
• These novel materials present a promising, cost-effective alternative to platinum catalysts for energy applications.