Due to the efficient and stable pollutant degradation properties, Fe^IV species from Fe-based single-atom catalysts (Fe-SACs) have garnered significant interest in advanced oxidation processes (AOPs). However, the microstructure and function of Fe^IV species in these processes remain contentious. In this study, we developed Au@SiO₂@Fe-SACs and utilized a combination of in situ surface-enhanced Raman spectroscopy, theoretical calculations, and synchrotron radiation techniques to elucidate the structure and functional mechanisms of Fe^IV species during AOPs. Our findings demonstrated that Fe-SACs with an Fe^IIN₄ structure were loaded on Au@SiO₂ to obtain Au@SiO₂@Fe-SACs. During PMS oxidation, a Raman peak associated with the Fe–O bonds appeared at 837 cm⁻¹ along with blue-shifts of Fe–N bonds from 183 cm⁻¹ and 322 cm⁻¹ to 191 cm⁻¹ and 335 cm⁻¹, proving the generation of Fe^IV species. Specifically, the elongation of the Fe–O bond displaced the Fe atom from the NC plane, resulting in an extension of the Fe–N bond length from 1.88 Å to 1.93 Å. Furthermore, the Fe^IV species directly oxidized typical pollutant phenol through a direct oxidation transformation pathway (DOTP) within a wide pH range of 3 to 9. They exhibited a significant increase in removal efficiency of phenol compared to the hydroxyl radicals (·OH) from activated H₂O₂ and effective reduction of total organic carbon (TOC). This study offers critical insights into the structural and functional attributes of Fe^IV species, providing valuable guidance for the design of more efficient Fe-SACs in AOPs.

中文翻译：

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原位拉曼研究高级氧化过程中 FeIV 物质的微观结构和功能


由于高效稳定的污染物降解特性，Fe 基单原子催化剂 （Fe-SAC） 中的 Fe^IV 物种在高级氧化过程 （AOP） 中引起了极大的兴趣。然而，Fe^IV 物质在这些过程中的微观结构和功能仍然存在争议。在这项研究中，我们开发了 Au@SiO₂@Fe-SACs，并结合了原位表面增强拉曼光谱、理论计算和同步辐射技术来阐明 AOPs 期间 Fe^IV 物种的结构和功能机制。我们的研究结果表明，具有 Fe^IIN₄ 结构的 Fe-SACs 在Au@SiO₂ 上加载以获得Au@SiO₂@Fe-SACs。在 PMS 氧化过程中，与 Fe-O 键相关的拉曼峰出现在 837 ^cm-1 处，同时 Fe-N 键从 183 ^cm-1 和 322 ^cm-1 蓝移到 191 ^cm-1 和 335 ^cm-1，证明了 Fe^IV 物质的产生。具体来说，Fe-O 键的伸长使 Fe 原子从 NC 平面上移开，导致 Fe-N 键长度从 1.88 Å 延长到 1.93 Å。此外，Fe^IV 物质在 3 至 9 的宽 pH 值范围内通过直接氧化转化途径 （DOTP） 直接氧化典型的污染酚。与羟基自由基 （·OH） 和有效还原总有机碳 （TOC）。 本研究为了解 Fe^IV 物种的结构和功能属性提供了重要见解，为在 AOPs 中设计更高效的 Fe-SACs 提供了有价值的指导。