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<p>Single-atom catalysts (SACs) have shown great potential in catalysis and energy-related applications. Among these, iron SACs stand out for their exceptional performance and environmental friendliness. In this study, we investigated the transformation of iron oxide nanoparticles into iron single atoms, exemplifying a top-down synthesis strategy. Using <i>in-situ</i> transmission electron microscopy (TEM), we directly observed the dynamic behaviors during the pyrolysis-induced atomization of Fe<sub>3</sub>O<sub>4</sub> nanoparticles along the [110], [111], and [112] zone axes at atomic-scale resolution. Reducing gases were supposed to release during the thermal pyrolysis of an organic reducing agent and facilitate the generation of Fe single atoms. The rate-limiting step was the reaction of these gases with atoms at surface steps and vertices of Fe<sub>3</sub>O<sub>4</sub> nanoparticles. Electron energy loss spectroscopy revealed a reduction in the Fe valence state and a transition in the Fe-O coordination environment after <i>in-situ</i> thermal treatment. The high-density dispersion of Fe single atoms was facilitated by the weak repulsive interactions between Fe atoms. This study enriches the understanding of the gas-assisted atomization mechanism and offers valuable insights for optimizing the production of high-density SACs. The methodology and findings can be extended to other material systems, broadening the scope of single-atom engineering and catalysis applications.</p>

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Atomic-scale Observation of the Generation and Dispersion of Iron Single Atoms

  • 期刊论文

  • 发表日期：

    2025年3月13日

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  • Ting Lin,
  • Yang Shen,
  • Mengshu Ge,
  • Yangfan Li,
  • Zhe Jiang,
  • Zhen-Hua Lyu,
  • Jian Liu,
  • Lin Gu,
  • Xiaozhi Liu

摘要

Single-atom catalysts (SACs) have shown great potential in catalysis and energy-related applications. Among these, iron SACs stand out for their exceptional performance and environmental friendliness. In this study, we investigated the transformation of iron oxide nanoparticles into iron single atoms, exemplifying a top-down synthesis strategy. Using in-situ transmission electron microscopy (TEM), we directly observed the dynamic behaviors during the pyrolysis-induced atomization of Fe3O4 nanoparticles along the [110], [111], and [112] zone axes at atomic-scale resolution. Reducing gases were supposed to release during the thermal pyrolysis of an organic reducing agent and facilitate the generation of Fe single atoms. The rate-limiting step was the reaction of these gases with atoms at surface steps and vertices of Fe3O4 nanoparticles. Electron energy loss spectroscopy revealed a reduction in the Fe valence state and a transition in the Fe-O coordination environment after in-situ thermal treatment. The high-density dispersion of Fe single atoms was facilitated by the weak repulsive interactions between Fe atoms. This study enriches the understanding of the gas-assisted atomization mechanism and offers valuable insights for optimizing the production of high-density SACs. The methodology and findings can be extended to other material systems, broadening the scope of single-atom engineering and catalysis applications.