Super-Dispersed Fe-N Sites Embedded into Porous Graphitic Carbon for ORR: Size, Composition and Activity Control

Searching for high-efficient, good long-term stability, and low-cost electrocatalysts toward oxygen reduction reaction (ORR) is highly desirable for the development of sustainable energy conversion devices. Iron-nitrogen doped carbon (Fe-N/C) catalysts have been recognized as the most promising candidates for traditional Pt-based catalysts that benefit from their high activity, excellent anti-poisoning ability, and inexpensiveness. Here, a super-dispersed and high-performance Fe-N/C catalyst was derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. It produced a series of catalysts, whose sizes could be tuned in the range from 62 to over 473 nm in diameter. After rationally regulating the component and heating treatment, the best ORR activity was measured for the catalyst with a size of 105 nm, which was obtained when the Fe³⁺/Zn²⁺ molar ratio was 0.05 and carbonization temperature was 900 °C. It exhibited a high onset potential (E_onset = 0.99 V) and half-wave potential (E_1/2 = 0.885 V) compared with a commercial 20% Pt/C catalyst (E_onset = 0.10 V, E_1/2 = 0.861 V) as well as much better durability and methanol resistance in an alkaline electrolyte.