Lin Pin-Jun, Yeh Chen-Hao, Jiang Jyh-Chiang
Department of Chemical Engineering, National Taiwan University of Science and Technology No. 43, Keelung Rd., Sec. 4, Da'an Dist. Taipei 10607 Taiwan
Department of Materials Science and Engineering, Feng Chia University No. 100, Wenhwa Rd., Seatwen Taichung 40724 Taiwan
RSC Adv. 2021 Nov 10;11(57):36257-36264. doi: 10.1039/d1ra06943h. eCollection 2021 Nov 4.
Fenton's reagent provides a method to produce active hydroxyl radicals (˙OH) for chemical oxidation by mixing iron oxide and hydrogen peroxide, which divides into homogeneous and heterogeneous Fenton's reagent. Heterogeneous Fenton's reagent is fabricated from HO and various iron oxide solid materials, such as α-FeOOH, α-FeO, and FeO. FeO possesses the Fe/Fe mixed valence oxidational state and has been reported to have good catalytic activity. However, the reaction mechanism of HO decomposition on FeO surfaces is still unclear. In this work, we performed DFT calculations to investigate the HO decomposition mechanisms over the FeO(311) surface. There are two iron environments for HO adsorption and decomposition on the FeO(311) surface, a Fe/Fe environment and a Fe/Fe environment. We found that the HO can adsorb on the Fe/Fe environment by molecular adsorption but by dissociative adsorption on the Fe/Fe environment. Our results show that both adsorption structures can produce two OH groups on the FeO(311) surface thermodynamically. In addition, based on the electronic property analysis, HO on the Fe/Fe environment follows the Haber-Weiss mechanism to form one OH anion and one OH radical. On the other hand, HO on the Fe/Fe environment follows the radical mechanism to form two OH radicals. In particular, the OH radical formed on Fe/Fe has energy levels on both sides of the Fermi energy level. It can be expected that this OH radical has good redox activity.
芬顿试剂提供了一种通过混合氧化铁和过氧化氢来产生活性羟基自由基（˙OH）以进行化学氧化的方法，该方法分为均相芬顿试剂和非均相芬顿试剂。非均相芬顿试剂由过氧化氢和各种氧化铁固体材料（如α-FeOOH、α-Fe₂O₃和Fe₃O₄）制成。Fe₃O₄具有Fe²⁺/Fe³⁺混合价氧化态，据报道具有良好的催化活性。然而，过氧化氢在Fe₃O₄表面的分解反应机理仍不清楚。在这项工作中，我们进行了密度泛函理论（DFT）计算，以研究过氧化氢在Fe₃O₄(311)表面的分解机理。在Fe₃O₄(311)表面，过氧化氢吸附和分解存在两种铁环境，一种是Fe²⁺/Fe³⁺环境，另一种是Fe³⁺/Fe³⁺环境。我们发现，过氧化氢可以通过分子吸附在Fe²⁺/Fe³⁺环境上，但在Fe³⁺/Fe³⁺环境上通过解离吸附。我们的结果表明，两种吸附结构在热力学上都可以在Fe₃O₄(311)表面产生两个羟基。此外，基于电子性质分析，Fe²⁺/Fe³⁺环境上的过氧化氢遵循哈伯-维西机制形成一个羟基阴离子和一个羟基自由基。另一方面，Fe³⁺/Fe³⁺环境上的过氧化氢遵循自由基机制形成两个羟基自由基。特别地，在Fe³⁺/Fe³⁺上形成的羟基自由基在费米能级两侧都有能级。可以预期，这种羟基自由基具有良好的氧化还原活性。
