Modulated selectivity in oxygen reduction for FeMn-based melamine framework via differential pyrolysis

Area of Science:

• Electrochemistry and Materials Science
• Catalysis for Energy Conversion

Background:

• Controlling the oxygen reduction reaction (ORR) selectivity is vital for energy technologies like fuel cells and batteries.
• The four-electron (4e-) ORR pathway is essential for fuel cells, while the two-electron (2e-) pathway produces hydrogen peroxide (H2O2).
• Achieving precise control over ORR pathways in catalysts remains a significant challenge.

Purpose of the Study:

• To develop a method for tailoring the ORR selectivity of FeMn-based catalysts.
• To investigate the impact of differential pyrolysis on catalyst active sites and ORR pathways.
• To achieve site-dependent ORR selectivity for targeted energy applications.

Main Methods:

• Differential pyrolysis of FeMn-based catalysts at varying rapid heating temperatures (10 °C/min).
• Synthesis of iron (Fe)-doped Mn2O3 nanoparticles on boron (B) and nitrogen (N) co-doped carbon nanosheets (FMO-BNC) (310-400 °C).
• Synthesis of dual-atom FeMn on B and N co-doped carbon (SAFM-BNC) (400-900 °C).
• Electrochemical characterization and computational simulations.

Main Results:

• FMO-BNC catalysts, prepared at lower temperatures (310-400 °C), selectively followed the 2e- ORR pathway, yielding 84.4% H2O2.
• SAFM-BNC catalysts, synthesized at higher temperatures (400-900 °C), facilitated the 4e- ORR pathway with a half-wave potential (E1/2 = 0.87 V) comparable to commercial Pt/C.
• Differential pyrolysis was shown to modulate catalyst active sites and optimize intermediate energetics for selective ORR.

Conclusions:

• Differential pyrolysis offers a feasible strategy to precisely control ORR selectivity in FeMn-based catalysts.
• Tailoring pyrolysis conditions enables the targeted production of either H2O2 (2e- pathway) or efficient ORR for fuel cells (4e- pathway).
• The findings provide insights into designing advanced catalysts for selective electrochemical reactions.