第一作者：Wenqian Li
通讯作者：何旭 副教授
通讯单位：哈尔滨工业大学环境学院
DOI:10.1016/j.apcatb.2024.124920
催化活性的增强往往伴随着选择性或稳定性的降低。在此，我们开发了以掺杂 N 的碳为载体、含有 FeMnN6 离子的铁锰二原子催化剂（Fe-Mn DACs），这种催化剂既保留了单原子催化剂（SACs）的高选择性，又由于相邻铁原子和锰原子之间的协同作用而提高了活性和稳定性。铁-锰 DAC 可在 5 分钟内实现 100% 的 2-氯苯酚（2-CP）降解，对高价金属氧（HVMO）生成的选择性接近 100%，过一硫酸盐（PMS）利用效率达到 100%，优于对应的 SAC 和之前报道的铁/锰基催化剂。多项实验证明，在锰 SAC 中引入铁元素可提高 Mn（IV）=O 的生成，从而增强 Mn 位点的催化活性。理论计算与实验相结合揭示了铁锰相互作用引发的带隙缩小和电子结构优化加强了铁锰 DAC 与 PMS 之间的轨道重叠和电子转移，从而促进了 PMS 的吸附、活化和 HVMO 的生成。稳定的异核 Fe(V)-O-O-Mn(IV) 物种的快速和可持续生成，同时实现了高活性、高选择性和高稳定性的污染物降解，有利于水净化应用。这项研究从原子层面揭示了 Fenton 类反应中 Fe-Mn 二原子位点的协同作用，对绿色环境修复具有重要意义。
Fig. 1. (a) Illustration of Fe-Mn DACs synthesis. (b) and (c) AC-HAADF-STEM images of Fe-Mn DACs. (d) Element mapping of Fe-Mn DACs with Fe (green), Mn(red), N(yellow), and C(blue) distribution.
Fig. 2. (a, b) XANES spectra and (c, d) FT-EXAFS spectra at the Fe and Mn K-edge of Fe SACs, Mn SACs, Fe-Mn DACs, and reference samples. (e, f) WT plots of EXAFS spectra at Fe K-edge of Fe SACs and Fe-Mn DACs, and (g, h) at Mn K-edge of Mn SACs and Fe-Mn DACs. (i-l) EXAFS fitting curves of Fe SACs, Mn SACs, and Fe-Mn DACs at Fe K-edge and Mn-edge in the R space.
Fig. 3. (a) 2-CP degradation and (b) PMS decomposition in PMS alone and different catalysts activated PMS systems at neutral pH. (c) In situ Raman spectra of PMS alone and different catalysts activated PMS systems at neutral pH. (d) Effects of different radical scavengers and acidic pH on 2-CP degradation kinetics in all catalytic oxidation systems. (e) PMSO consumption and PMSO2 generation in all catalytic oxidation systems. (f) ESR spectra of PMS, catalysts, and catalysts/PMS systems. (g) ESR spectra for 1O2 detection with 2,2,6,6-tetra-methyl-4-piperidinol (TEMP) as the trapping agent. (h) Effect of pre-mixing time and (i) pre-adsorption time on the 2-CP oxidation in the Fe-Mn DACs/PMS system.
Fig. 4. (a) Reaction pathway of PMS activation on Fe-Mn DACs for the generation of HVMO species. (b) Potential energy profiles of the reaction pathway for the generation of HVMO species. (c) Electron density difference for PMS adsorption on Fe SACs, Mn SACs, Fe-Mn DACs (Fe and Mn sites) and the corresponding charge transfer. (d) Projected DOSs of PMS absorbed on Fe sites in FeN4 and FeMnN6. (e) Projected DOSs of PMS absorbed on Mn sites in MnN4 and FeMnN6. (f) Projected DOSs of Fe 3d orbital in Fe SACs and Fe-Mn DACs. (g) Projected DOSs of Mn 3d orbital in MnN4 and FeMnN6.
Fig. 5. (a) Photograph of the continuous flow Fenton-like filter experiment device (MB as an indicator pollutant). (b) 2-CP removal performance of the treatment equipment with catalyst, and metal ion concentration in the effluent with filtration time. (c) Optimized structure, HOMO, LUMO, and ESP mapping of 2-CP. (d) Ecotoxicity effect of 2-CP and its degradation intermediates on the E. Coli growth.
在此，我们通过简便的两步热解方法开发出了一种具有高活性、高选择性和高稳定性的铁锰 DAC，并揭示了 PMS-AOPs 中铁锰二原子位点的协同催化氧化机制。在 100% 利用 PMS 几乎 100% 选择性生成 HVMO 和 100% 去除污染物方面，Fe-Mn DACs 的性能优于单原子 DACs。实验和理论分析表明，相邻铁-锰位点引发的带隙变窄和电子结构优化加强了铁-锰 DAC 与 PMS 之间的轨道重叠和电子转移，从而促进了 PMS 的吸附、活化和 HVMO 的生成。铁锰 DAC 上增强的传质有利于 HVMO 的利用。此外，由于催化剂构型的形成能较低，FeV=O 和 MnIV=O 转化为更稳定的 FeV-O-O-MnIV 物种，已建立的非辐射 Fe-Mn 双原子活化 PMS 系统具有环境稳健性和出色的长期稳定性。这项工作通过从机理上理解增强 Fenton 类反应中的催化活性和稳定性，推动了 DAC 的发展。
Wenqian Li, Lingyu Kong, Zhenyi Wang, Ziwen Han, Bin Zhang, Miao Shi, Kun Qian, Jiaxuan Yang, Xu He, Jun Ma, Electronic structure reconstruction of Fe-Mn diatomic pair for disentangling activity-stability tradeoff in Fenton-like reactions, Applied Catalysis B: Environment and Energy, 2025, https://doi.org/10.1016/j.apcatb.2024.124920
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