Transition metal single-atom catalysts (SACs) have been widely used in oxygen reduction reactions (ORR) and oxygen evolution reaction (OER) due to its greatest atomic utilization and low costs, which catalytic performance can be further enhanced by electron distribution adjustment. Herein, we synthesized a carbon-encapsulated FeS/FeC nanoparticles doped carbon-based Fe single atom catalyst from fluid catalytic cracking (FCC) slurry though a one-pot pyrolysis. The synergistic effect between FeS/FeC nanoparticles and Fe single atom structure (FeN) promotes the ORR/OER processes, which may due to the reduction of the adsorption free energy of intermediates. Meanwhile, the polyaromatic hydrocarbon in FCC slurry enhances the graphitization of catalyst to facilitate charge transfer in electrocatalysis process, and the carbon-encapsulated nanoparticles sites possess higher stability and dispersion. As a result, the optimized catalyst (FeS/FeC@Fe-N-C) presents a high nanoparticles dispersion and graphitization level, which has a higher ORR catalytic ability (E = 0.91 V vs RHE) compared with commercial Pt/C (20 wt%, E = 0.879 V vs RHE) and a similar OER catalytic ability (E = 0.1.506 V vs RHE) compared with RuO (E = 1.518 V vs RHE). A liquid Zn-air battery assembled with FeS/FeC@Fe-N-C show a peak power density of 113 mW cm and an open potential of 1.432 V. This work sheds light on a new method to design transition metal active sites carbon based single-atom catalyst for enhanced ORR and OER processes.

中文翻译：

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分布在 Fe-NC 中的高度分散的碳封装 FeS/Fe3C 纳米粒子，用于增强氧电催化和锌空气电池

过渡金属单原子催化剂（SAC）因其最大的原子利用率和较低的成本而被广泛应用于氧还原反应（ORR）和析氧反应（OER），并且通过电子分布调整可以进一步增强其催化性能。在此，我们通过一锅热解从流化催化裂化（FCC）浆料中合成了碳包封的 FeS/FeC 纳米粒子掺杂的碳基铁单原子催化剂。 FeS/FeC纳米颗粒与Fe单原子结构（FeN）之间的协同效应促进了ORR/OER过程，这可能是由于中间体吸附自由能的降低所致。同时，FCC浆料中的多环芳烃增强了催化剂的石墨化，有利于电催化过程中的电荷转移，并且碳包封的纳米粒子位点具有更高的稳定性和分散性。因此，优化后的催化剂（FeS/FeC@Fe-NC）呈现出较高的纳米粒子分散度和石墨化水平，与商用 Pt/C（20 wt%）相比，其具有更高的 ORR 催化能力（E = 0.91 V vs RHE） ，E = 0.879 V vs RHE）和与 RuO（E = 1.518 V vs RHE）类似的 OER 催化能力（E = 0.1.506 V vs RHE）。用 FeS/FeC@Fe-NC 组装的液态锌空气电池的峰值功率密度为 113 mW cm，开路电位为 1.432 V。这项工作揭示了一种设计过渡金属活性位点碳基单电池的新方法。用于增强 ORR 和 OER 过程的原子催化剂。