Fe-N_x Sites Enriched Carbon Micropolyhedrons Derived from Fe-Doped Zeolitic Imidazolate Frameworks with Reinforced Fe-N Coordination for Efficient Oxygen Reduction Reaction

Abstract

Rational design and facile synthesis of highly active and stable electrocatalysts for oxygen reduction reaction (ORR) are crucial in the field of metal-air batteries. Here, we present a facile two-stage thermal synthesis of Fe-N codoped porous carbon (Fe-N/C) with abundant Fe-N x active sites and mesopores from Fe-doped ZIF-8 precursors. The first-stage preheating treatment of the Fe-doped ZIF-8 precursors before the second-stage carbonization is the key to boost the coordination between the doped Fe and N-containing ligands, which contributes to a higher N content and more Fe-N x sites in the final carbonized product. Besides, the preheating and Fedoping both affect the morphology, porous structure, and catalytic performance of the fabricated Fe-N/C. The optimized Fe-N/C catalyst exhibits an outstanding ORR catalytic performance with a half-wave potential of 0.88 V and limiting current density of 6.0 mA cm −2 in 0.1 M KOH. A Mg-air battery assembled with a neutral electrolyte using the optimized Fe-N/C catalyst as the cathode exhibits an excellent power density of 72 mW cm −2 at 0.72 V. This developed two-stage synthesis strategy is facile, and the preheating stage could be integrated into any carbonization process as an intermediate step for the fabrication of various metal, N codoped carbon materials with enhanced electrocatalytic performance.

Efficient Oxygen Reduction Catalysts of Porous Carbon Nanostructures Decorated with Transition Metal Species

“…Biomass always contains carbon‐based protein and other inorganic salts with low cost and abundant resources, which can be pyrolyzed into porous carbon nanostructures decorated with TM species. For example, animal bones (e.g., cattle bone,36 fish scale,37 peanuts,38 etc.) are one kind of the biomass wastes, which have been widely employed as low‐cost and environment‐friendly precursors to synthesize the hierarchically porous carbon‐based nanostructures.…”

Iron and nitrogen codoped carbon catalyst with excellent stability and methanol tolerance for oxygen reduction reaction

“…We think the formation of Fe 3 N active sites embedded in the carbon matrix of the Fe x NC catalysts was responsible for the high activity and stability. The configuration of Fe‐N could significantly decrease the Mullilken charges of the Fe center, which favored the adsorption of O 2 molecule on the Fe 3 N active sites and thus facilitated the subsequent dissociation of the double bond of O 2 …”

“…The configuration of Fe-N could significantly decrease the Mullilken charges of the Fe center, which favored the adsorption of O 2 molecule on the Fe 3 N active sites and thus facilitated the subsequent dissociation of the double bond of O 2 . 74,75 For DMFCs, the penetration of methanol from anode to cathode would increase the overpotential of ORR at the cathode. Therefore, it is crucial for the ORR catalyst to have a high methanol tolerance ability.…”

Homogenous Meets Heterogenous and Electro‐Catalysis: Iron‐Nitrogen Molecular Complexes within Carbon Materials for Catalytic Applications

“…who found that a pre‐heating step of the Fe‐ZIF‐8 precursor (200 °C) before carbonisation (800 °C) was key in boosting the coordination between the doped Fe and N‐containing ligands (Figure ). Their optimised catalysts reached ORR catalytic performance with a half‐wave potential of 0.88 V and limiting current density of 6.0 mA cm −2 in 0.1 M KOH …”

“… Two‐steps synthesis of FeN x @C, electrochemical performance. Reproduced with permission from . Copyright 2018 American Chemical Society.…”