An iron porphyrin-based conjugated network wrapped around carbon nanotubes as a noble-metal-free electrocatalyst for efficient oxygen reduction reaction

Abstract

Developing an efficient, robust, and noble-metal-free catalyst for the oxygen reduction reaction (ORR) is crucial for the large-scale commercialization of fuel cells and metal–air batteries. Herein, we report a structurally well-defined iron porphyrin-based conjugated network on carbon nanotubes ((FeP)_n-CNTs) as a novel electrocatalyst for the ORR. Its superior electrocatalytic activity toward the ORR is demonstrated by the high-performance catalytic activity of (FeP)_n-CNTs with a positive ORR onset potential and half-wave potential (E_1/2 ∼ 0.76 V vs. RHE) values as well as outstanding durability and methanol tolerance in alkaline media. In addition, the low H₂O₂ yield illustrates that the ORR occurs mainly via the direct four-electron (4e⁻) pathway, and testing shows that the small amount of produced H₂O₂ can be rapidly consumed through both electrochemical reduction and oxidation. Our results demonstrate that the as-prepared (FeP)_n-CNT catalyst is a promising noble-metal-free catalyst for potential applications in fuel cells and metal–air batteries.