Breaking a Molecular Scaling Relationship Using an Iron–Iron Fused Porphyrin Electrocatalyst for Oxygen Reduction

• Published in: Journal of the American Chemical Society Vol. 146; no. 17; pp. 11622 - 11633
• Main Authors: Nishiori, Daiki, Menzel, Jan Paul, Armada, Nicholas, Reyes Cruz, Edgar A., Nannenga, Brent L., Batista, Victor S., Moore, Gary F.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01-05-2024
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.3c08586

The design of efficient electrocatalysts is limited by scaling relationships governing trade-offs between thermodynamic and kinetic performance metrics. This ″iron law″ of electrocatalysis arises from synthetic design strategies, where structural alterations to a catalyst must balance nucleophilic versus electrophilic character. Efforts to circumvent this fundamental impasse have focused on bioinspired applications of extended coordination spheres and charged sites proximal to a catalytic center. Herein, we report evidence for breaking a molecular scaling relationship involving electrocatalysis of the oxygen reduction reaction (ORR) by leveraging ligand design. We achieve this using a binuclear catalyst (a diiron porphyrin), featuring a macrocyclic ligand with extended electronic conjugation. This ligand motif delocalizes electrons across the molecular scaffold, improving the catalyst’s nucleophilic and electrophilic character. As a result, our binuclear catalyst exhibits low overpotential and high catalytic turnover frequency, breaking the traditional trade-off between these two metrics.