哈工大马军院士团队赵雨萌课题组、中国石油大学孔德桢文章ACB：重新审视直接电子转移氧化系统设计：热力-流体性质协控机制
图文摘要
成果简介
近日，哈尔滨工业大学赵雨萌与中国石油大学（华东）孔德桢等在Applied Catalysis B: Environment and Energy上发表了题为“Revisiting the design of direct-electron-transfer oxidation systems: Synergistic roles of thermodynamic and hydrodynamic properties”的研究论文(DOI: 10.1016/j.apcatb.2025.125448)。本文通过构建钴纳米颗粒功能化碳纳米管（Co-CNT）/过氧乙酸（PAA）催化过滤体系，系统探究了热力学（活性位点设计、氧化还原电位调控）与流体动力学（扩散边界层减薄、对流增强传质）性质对直接电子转移（DET）介导的过氧化物高级氧化技术的协同增效机制，打破传统催化剂改性单维度优化局限。
全文速览
DET介导的过氧化物高级氧化技术，已成为处理难降解新兴微污染物的前沿手段。当前研究多聚焦于催化剂改性以提升水处理效能，但热力学与流体动力学协同优化这一系统性策略仍鲜有探索。本研究通过构建Co-CNT膜，揭示了热力学与流体动力学因素对PAA活化的关键作用。相较于CNT/PAA过滤体系，该过滤系统对4-氯苯酚的去除率提升超50%，反应动力学速率较间歇式反应器快145倍，且在4.3秒内实现完全降解。钴纳米颗粒通过高电荷累积效应强化了PAA的吸附与活化，从热力学层面提升了DET系统的整体氧化电位，促进电子从微污染物向催化剂表面的转移。进一步的流体动力学模拟发现，过滤过程中的对流与空间限域效应使扩散边界层厚度较间歇式反应器缩小两个数量级，扩散时间尺度显著低于对流时间尺度。这一流体动力学特性增强了反应物向催化剂表面的对流增强传质，并大幅提升了反应物与催化剂表面的碰撞频率。本研究为DET介导的过氧化物高级氧化体系设计提供了新思路，强调热力学与流体动力学协同优化对提升水处理催化效率的必要性，为高效降解微污染物提供了理论支撑。
引言
以DET介导的过氧化物高级氧化技术凭借其高可持续性与选择性，成为处理新兴微污染物的潜力方案。然而，传统间歇式反应器因反应物传质受限导致降解效率难以突破瓶颈。本研究提出，热力学与流体动力学协同调控是突破以DET介导的过氧化物高级氧化技术性能极限的关键，并通过连续流Co-CNT/PAA过滤系统首次实现了对DET介导PAA体系的热力学与流体力学特性同步优化。
图文导读
Co-CNT/PAA催化过滤体系构建
Fig. 1. Fabrication and characterization of the Co-CNT/CM.
真空过滤与电沉积结合制备了Co-CNT/CM复合材料。综合表征手段证明Co-CNT/CM兼具交织微观结构、适度亲水性、高导电性、均匀Co掺杂及渗透性，为后续催化应用奠定基础。当污染物4-氯苯酚流经膜时，Co-CNT/PAA过滤系统的渗透液中4-氯苯酚去除率高达100%（停留时间仅4.3秒）；而未经膜过滤时，出水4-氯苯酚去除率仅为22%。这一显著差异表明，Co-CNT/CM系统通过催化降解与对流强化传质的协同作用显著提升了污染物去除效率。
催化机理证明
Fig. 2. Reaction mechanism analysis of the Co-CNT/PAA system involving radical and non-radical pathways. (a) ESR spectra of TEMPO in the pure PAA and Co-CNT/PAA system. (b) Comparison of 4-CP removal in the Co-CNT/PAA system using a solution of H2O and D2O, respectively. (c)ESR spectra of DMPOX in the pure PAA, CNT, and Co-CNT/PAA system. (d) The influence of different quenchers on 4-CP degradation in the Co-CNT/PAA system. (e) Fluorescence spectra of TAOH in pure PAA, Co-CNT, and Co-CNT/PAA systems. (f) NB and CBZ removal in the Co-CNT/PAA system. (g) The concentration variation of PMSO and PMSO2 in the Co-CNT/PAA system. (h) Premixing experiments in the Co-CNT/PAA system. (i) Open-circuit potential curves of the GCE electrode and different CNT electrodes upon PAA and 4-CP addition. (j) Current-time curves with or without 4-CP under different potentials.(k) In situ Raman spectra of H2O2, CH3COOH, Co-CNT, PAA, Co-CNT/PAA, and Co-CNT/PAA/BPA in the liquid solution.
EPR实验、探针实验、猝灭实验、预混合实验、电化学测试和原位拉曼表征等共同证实了Co-CNT/PAA催化体系主要的反应机制为直接电子转移。
Co掺杂增强DET介导体系热力学的机理证明
Fig. 3. Mechanism for thermodynamic enhancement of the DET-mediated system via Co doping. (a) Comparison of O-O bond length of pristine PAA, PAA adsorbed on CNT (PAA-1), and PAA adsorbed on Co-CNT (PAA-2). (b) Comparison of C-O bond length of pristine PAA, PAA-1, and PAA-2. (c) Comparison of adsorption energy of PAA adsorbed on CNT and Co-CNT. (d) Comparison of electron transfer quantity when PAA adsorbed on CNT and Co-CNT. (e, f) Top view of optimized adsorption configuration and differential charge density of PAA adsorbed on CNT (configuration I) and PAA adsorbed on Co-CNT (configuration II). (g) Molecular orbital energies of PAA and 4-CP. HOMO and LUMO indicate the highest occupied molecular orbital and the lowest unoccupied molecular orbital, respectively. Reaction pathway of PAA activation on (h) CNT and (i) Co-CNT. IS, TS, and FS denote the initial structure, transition structure, and final structure, respectively.
理论计算证实Co掺杂通过调控CNT上的电子分布、增强PAA吸附及电荷转移能力，同时降低活化能，热力学上促进了高效电子转移与污染物降解。
连续流过滤实现DET介导体系流体动力学性能强化的作用机制
Fig. 4.Mechanism for hydrodynamic enhancement of the DET-mediated system via flow-through filtration.COMSOL simulation of the velocity vector field in the (a) flow-by and (b) flow-through mode (The grey lines represent the CNT layers in the Co-CNT membrane). COMSOL simulation of the velocity field in the (c) flow-by and (d) flow-through mode. Schematic illustration of the diffusive transport in the (e) flow-by and (f) flow-through mode (The royal-blue arrow designates the direction of convective transport, and orange arrows indicate the direction of diffusive transport). (g) Outlet concentration of flow-by and flow-through modes under an initial bisphenol concentration of 0.005 mol m-3. (h) Current comparison between the flow-by and flow-through mode in the Co-CNT/PAA system. (i) Mechanism illustration of advection-enhanced mass transport in the Co-CNT/PAA catalytic filtration system (the left inset depicts the structural characteristics and flow-through operation modes of Co-CNT CM, and the right inset describes the mechanism for micropollutant removal due to the enhanced PAA adsorption and advection-enhanced mass transport).
COMSOL模拟证明过滤模式边界层厚度<150 nm，然而间歇模式边界层厚度>1.5 μm，存在传质瓶颈。此外，过滤模式可以提升催化活性位点利用率，过滤模式中双酚A出口浓度显著低于间歇模式。恒电流测试显示，过滤模式稳态电流（0.53 mA）较间歇模式（0.036 mA）高一个量级，进一步印证了强制过滤压缩扩散边界层、加速传质。最后，通过扩散时间尺度与对流时间尺度对比，证实Co-CNT/PAA催化过滤体系需极高流速（5.4×10³ m·s⁻¹）才触发扩散限制。实际运行流速（1.08×10⁻³ m·s⁻¹）远低于阈值，表明过滤模式有效规避间歇反应的扩散限制，实现传质-反应高效协同。
实际应用
Fig. 5. Practicality evaluation of the Co-CNT/PAA catalytic filtration system. (a) Co leakage in the Co-CNT/PAA catalytic filtration system. (b) Removal efficiency of 4-CP in the Co-CNT/PAA catalytic filtration system under different pH conditions. (c) Removal efficiency of 4-CP in the Co-CNT/PAA catalytic filtration system under different anions. (d) Removal efficiency of 4-CP in the Co-CNT/PAA catalytic filtration system under real water matrices. (e) Structures of recalcitrant micropollutants. (f) Micropollutant removal performance in the permeate of the Co-CNT/PAA filtration system after filtering 85 ml feed solution.
Co-CNT/PAA体系在宽pH范围、复杂水质中均表现出高效污染物去除能力，兼具低金属浸出风险与多污染物广谱降解特性，为实际水处理应用提供可靠解决方案。
小结
DET介导的基于过氧化物的高级氧化工艺处理新污染物前景良好，但间歇式工艺受扩散传质限制。研究发现，Co-CNT/PAA 过滤系统能同时调控 DET 介导的 PAA 系统的热力学和流体力学特性，大幅提升水净化动力学。其高新污染物去除效率得益于氧化电位提升和平流增强传质，这分别由 Co NPs 促进 PAA 积累及增强导电性、强制过滤压缩扩散边界层及加速传质实现。热力学与流体力学的协同增强使过氧化物活化突破传统限制，研究强调二者协同调控对提升水净化性能的重要性，倡导同时优化这两个性质以推进基于过氧化物技术的应用。
