Porphyrin Polymer-Derived Single-Atom Fe Assisted by Fe2o3 with Oxygen Vacancy for Efficient Oxygen Reduction Reaction

Abstract

Single-atom catalysts (SACs) have been deemed as one of the most prospective substitutes for high-efficiency oxygen reduction reaction (ORR) catalysts due to its theoretical maximum atomic utilization. However, the convenient preparation and the further improvement in activity of SACs are laborious. Herein, the N-doped porous carbon (NC) material with in site produced Fe-N4 single-atom catalytic sites (FeSA) accompanied by Fe2O3 species with abundant oxygen vacancies (Ov-Fe 2O3) as co-catalytic sites (Ov-Fe2O3@FeSA@NC) is successfully obtained by using a well-designed porphyrin conjugated mesoporous polymer (CMP) consisting of iron porphyrin and metal free porphyrin units as a precursor, and followed by pyrolysis. A series of controllable experiments reveal that FeSA assisted by Ov-rich Fe 2O3 render Ov-Fe2O3@FeSA@NC outstanding ORR activity in the alkaline medium with the onset and half-wave potentials (Eonset and E1/2 ) of 0.987 V and 0.901 V vs RHE, which significantly outperformed the electrochemical activity of FeSA@NC (Eonset =0.962 V, E1/2 =0.850 V) and Ov-Fe2O3@NC (Eonset =0.913 V, E1/2 =0.821 V) with individual FeSA and Ov-Fe2O3 active sites, respectively. This work innovatively demonstrates the importance of oxygen vacancy-assisted single-atom catalysts for oxygen reduction catalysis, and also provides guidance for the design of high-performance SACs.

Keywords: oxygen reduction reaction, Fe2O3, Oxygen vacancy, porphyrin conjugated mesoporous polymer, zinc-air battery