State Key Laboratory of Hydraulics and Mountain River Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China; Sino-German Centre for Water and Health Research, Sichuan University, Chengdu 610041, China.
State Key Laboratory of Hydraulics and Mountain River Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China.
Water Res. 2022 Feb 15;210:117984. doi: 10.1016/j.watres.2021.117984. Epub 2021 Dec 19.
The sluggish kinetics of Fe(II) recovery strongly impedes the scientific progress of Fenton reaction (Fe(II)/HO) towards practical application. Here, we propose a novel mechanism that metal-free nitrogen-doped carbon nanotubes (NCNT) can enhance Fenton chemistry with HO as electron donors by elevating the oxidation potential of Fe(III). NCNT remarkably promotes the circulation of Fe(III)/Fe(II) to produce hydroxyl radical (OH) with excellent stability for multiple usages (more than 10 cycles) in the NCNT/Fe(III)/HO system. Although carbonyl on NCNT can act as the electron supplier for Fe(III) reduction, the behavior of NCNT is distinct from common reductants such as hydroxylamine and boron. Electrochemical analysis and density functional theory calculation unveil that nitrogen sites of NCNT can weakly bind with Fe(III) to elevate the oxidation potential of Fe(III) (named near-free Fe(III), primarily FeOH) at pH ranging from 2.0 to 4.0. Without inputs of external stimulations or electron sacrificers, near-free Fe(III) can promote HO induced reduction of Fe(III) to initiate Fenton chain reactions for long-lasting generation of OH. To our delight, it is a common property of N-doped carbon materials (e.g., graphene, carbon nanofibers, and acetylene black), our research thus provides a novel, sustainable, and green strategy for promoting Fenton chemistry.
铁(II)回收的缓慢动力学强烈阻碍了芬顿反应（Fe(II)/HO）在实际应用中的科学进展。在这里，我们提出了一种新的机制，即无金属氮掺杂碳纳米管（NCNT）可以通过提高 Fe(III)的氧化电位来增强芬顿化学，HO 作为电子供体。NCNT 显著促进了 Fe(III)/Fe(II)的循环，在 NCNT/Fe(III)/HO 体系中具有优异的稳定性，可多次（超过 10 次循环）产生羟基自由基（OH）。尽管 NCNT 上的羰基可以作为 Fe(III)还原的电子供体，但 NCNT 的行为与常见的还原剂如羟胺和硼不同。电化学分析和密度泛函理论计算揭示了 NCNT 的氮位可以与 Fe(III)弱结合，从而在 pH 值为 2.0 至 4.0 范围内提高 Fe(III)的氧化电位（称为近自由 Fe(III)，主要是 FeOH）。在没有外部刺激或电子牺牲剂输入的情况下，近自由 Fe(III)可以促进 HO 诱导的 Fe(III)还原，引发芬顿链反应，从而长时间持续产生 OH。令我们高兴的是，这是 N 掺杂碳材料（如石墨烯、碳纳米纤维和乙炔黑）的共同特性，因此我们的研究为促进芬顿化学提供了一种新的、可持续的和绿色的策略。
