Metallocorroles as Nonprecious-Metal Catalysts for Oxygen Reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Affordable fuel cells require efficient, earth-abundant catalysts for the oxygen reduction reaction (ORR).
• Platinum-based catalysts are effective but expensive, hindering widespread adoption.
• Developing non-platinum catalysts is crucial for advancing fuel cell technology.

Purpose of the Study:

• To investigate the catalytic activity of earth-abundant trivalent metal complexes of β-pyrrole-brominated corrole for the ORR.
• To evaluate the performance of these complexes adsorbed on a high-surface-area carbon support.
• To understand the structure-activity relationships of different metal centers in corrole-based ORR catalysts.

Main Methods:

• Synthesis and characterization of trivalent Mn, Fe, Co, Ni, and Cu complexes of β-pyrrole-brominated corrole.
• Preparation of composite materials by adsorbing metal corrole complexes onto BP2000 carbon powder.
• Electrochemical measurements in acidic aqueous solutions to assess ORR catalytic activity.
• Spectroscopic and computational methods to analyze the electronic properties of the metallocorroles.

Main Results:

• Catalytic activity varied significantly with the central metal ion, following the order Co>Fe>Ni>Mn>Cu.
• The Co(III) corrole complex exhibited the best performance, with an onset potential of 0.81 V versus the reversible hydrogen electrode (RHE).
• Composite materials demonstrated effective ORR catalysis in acidic media.

Conclusions:

• Earth-abundant metal corrole complexes, particularly cobalt, are promising alternatives to platinum for ORR catalysis.
• The electronic structure and metal center play a critical role in determining the catalytic efficiency.
• This study provides a foundation for designing next-generation, cost-effective fuel cell catalysts.