Circumventing Scaling Relations in Oxygen Electrochemistry Using Metal-Organic Frameworks

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Unfavorable scaling relationships between key oxygen intermediates (*OOH, *OH, *O) lead to high overpotentials in oxygen electrochemistry.
• Existing strategies to overcome these limitations in traditional catalysts lack experimental validation for heterogeneous systems.
• Developing novel catalysts that circumvent these scaling relations is a critical challenge.

Purpose of the Study:

• To investigate bimetallic porphyrin-based MOFs (PMOFs) as a platform for designing 3-D active site environments for the oxygen reduction reaction (ORR).
• To demonstrate the potential of PMOFs to overcome scaling limitations in oxygen electrochemistry through rational design.

Main Methods:

• Utilized density functional theory (DFT) calculations to model and analyze the electronic and binding properties of bimetallic PMOFs.
• Systematically tuned transition metal active sites, spectator ligands, and MOF topologies to optimize catalytic performance.

Main Results:

• DFT calculations confirm that bimetallic PMOFs can effectively tune *OOH binding energy and theoretical limiting potentials.
• Predicted theoretical limiting potentials reached up to 1.07 V for Fe/Cr-PMOF-Al, surpassing the performance of Pt/C for the 4e-ORR.
• Demonstrated the influence of active site composition, spectator groups, and MOF structure on ORR activity.

Conclusions:

• Bimetallic porphyrin-based MOFs offer a promising materials platform for designing efficient heterogeneous catalysts for the oxygen reduction reaction.
• The rational design of active site environments within PMOFs can overcome traditional scaling limitations.
• This work establishes PMOFs as a viable candidate for future experimental and theoretical investigations in ORR catalysis.