State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China.
Department of Energy Engineering, Korea Institute of Energy Technology (KENTECH), Naju 58330, Korea.
Water Res. 2024 May 1;254:121417. doi: 10.1016/j.watres.2024.121417. Epub 2024 Mar 4.
Single-atom catalysts (SACs) have emerged as competitive candidates for Fenton-like oxidation of micro-pollutants in water. However, the impact of metal insertion on the intrinsic catalytic activity of carrier materials has been commonly overlooked, and the environmental risk due to metal leaching still requires attention. In contrast to previous reports, where metal sites were conventionally considered as catalytic centers, our study investigates, for the first time, the crucial catalytic role of the carbon carrier modulated through hetero-single-atom dispersion and the regulation of Fenton-like oxidation pathways. The inherent differences in electronic properties between Fe and Co can effectively trigger long-range electron rearrangement in the sp-carbon-conjugated structure, creating more electron-rich regions for peroxymonosulfate (PMS) complexation and initiating the electron transfer process (ETP) for pollutant degradation, which imparts the synthesized catalyst (FeCo-NCB) with exceptional catalytic efficiency despite its relatively low metal content. Moreover, the FeCo-NCB/PMS system exhibits enduring decontamination efficiency in complex water matrices, satisfactory catalytic stability, and low metal leaching, signifying promising practical applications. More impressively, the spatial relationship between metal sites and electron density clouds is revealed to determine whether high-valent metal-oxo species (HVMO) are involved during the decomposition of surface complexes. Unlike single-type single-atom dispersion, where metal sites are situated within electron-rich regions, hetero-single-atom dispersion can cause the deviation of electron density clouds from the metal sites, thus hindering the in-situ oxidation of metal within the complexes and minimizing the contribution of HVMO. These findings provide new insights into the development of carbon-based SACs and advance the understanding of nonradical mechanisms underpinning Fenton-like treatments.
单原子催化剂（SACs）已成为水相中类芬顿氧化去除微污染物的有竞争力的候选者。然而，金属插入对载体材料固有催化活性的影响通常被忽视，而且由于金属浸出而带来的环境风险仍需要关注。与以往的报告不同，其中金属位点通常被认为是催化中心，我们的研究首次调查了通过杂原子单分散和调节类芬顿氧化途径来调制的碳载体的关键催化作用。Fe 和 Co 之间固有电子性质的差异可以有效地在 sp 碳共轭结构中引发长程电子重排，为过一硫酸盐（PMS）络合创造更多富电子区域，并引发污染物降解的电子转移过程（ETP），这使得合成的催化剂（FeCo-NCB）尽管金属含量相对较低，但具有出色的催化效率。此外，FeCo-NCB/PMS 体系在复杂水基质中表现出持久的去污效率、令人满意的催化稳定性和低金属浸出，表明具有有前景的实际应用。更令人印象深刻的是，揭示了金属位点和电子密度云之间的空间关系，以确定在表面络合物分解过程中是否涉及高价金属-氧物种（HVMO）。与金属位点位于富电子区域的单型单原子分散不同，杂原子单分散会导致电子密度云从金属位点偏离，从而阻碍了复合物内金属的原位氧化，并最大限度地减少了 HVMO 的贡献。这些发现为开发基于碳的 SAC 提供了新的见解，并推进了对类芬顿处理所基于的非自由基机制的理解。
