Concave and Convex Molecular Curvature Modulates Spatial Electronic Environments for Controlled Electrocatalysis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Molecular catalysts offer tunable active sites for precise chemical reactions.
• Local curvature environment's role in modulating catalyst activity is not well understood.
• Iron phthalocyanines (FePc) are known catalysts, but their pathway selectivity is debated.

Purpose of the Study:

• To investigate how local concave and convex architectures influence the catalytic properties of FePc.
• To understand the mechanism behind curvature-dependent selectivity in oxygen reduction reactions.
• To establish a general design principle for engineering molecular catalysts via curvature.

Main Methods:

• Synthesized FePc on concave (mesoporous carbon) and convex (inverse architecture) supports.
• Performed electrochemical testing to evaluate oxygen reduction reaction (ORR) pathways.
• Utilized in situ electrochemical infrared spectroscopy and theoretical calculations to probe reaction mechanisms.

Main Results:

• Convex-FePc preferentially catalyzes the four-electron ORR pathway (O2 to H2O).
• Concave-FePc favors the two-electron ORR pathway, producing H2O2 with >80% selectivity.
• Curvature modulates Fe site electronic properties and intermediate interactions, influencing selectivity.

Conclusions:

• Local geometric curvature is a critical factor in controlling molecular catalyst activity and selectivity.
• The findings provide a general framework for designing catalysts by manipulating curvature.
• This approach is applicable to other molecular catalysts (CoPc, MnPc) and reactions (CO2 reduction).