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Kinetic Study of Photoelectrochemical Oxidation of Lignin Model Compounds on TiO2 Nanotubes

Abstract

本文用电化学方法制备了二氧化钛纳米管,并用扫描电子显微镜和X 衍射对其形貌及组成进行了表征. 进一步研究了木质素的两个模型化合物, 1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy) -1,3-propanediol (DMP) and 3-hydroxy-1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanone (HDM),在二氧化钛纳米管上的光电氧化. 在DMP的光电氧化过程中, 一个新的紫外吸收峰出现在波长304 nm处. 虽然中间体的形成速率随着浓度的增加而增加, 却随着温度的增加而减少. 尽管HDM 和DMP在结构上有很小的差别, 在氧化过程中DMP却呈现出很小的吸光度变化, 表明HDM 不易被光电氧化. 量子化学计算结果也表明,DMP更容易被氧化, 这个结果与光电氧化的结果相吻合.In this study, TiO2 nanotubes were prepared via the electrochemical oxidation of titanium substrates in a non-aqueous electrolyte and their morphology and microstructures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoelectrochemical oxidation of two lignin model compounds, 1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanediol (DMP) and 3-hydroxy-1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanone (HDM), was investigated. A new band appeared at ~304 nm during the photoelectrochemical oxidation of DMP. The rate of DMP intermediate formation was amplified with the increase of initial concentrations, while it was diminished with increased temperature. Despite the similarity in structure between HDM and DMP, there are only small increases in absorbance during the oxidation of HDM, suggesting that HDM is less reactive. Quantum chemical calculations based on the density functional theory (DFT) were performed in order to link photoelectrochemical reactivity with specific molecular properties. Relatively higher ELUMO-EHOMO of HDM makes it more stable and thus more refractory to oxidation, which is consistent with our photoelectrochemical results.This work was supported by a Strategic Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC). A. Chen acknowledges NSERC and the Canada Foundation of Innovation (CFI) for the Canada Research Chair Award in Materials and Environmental ChemistryThis work was supported by a Strategic Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC). A. Chen acknowledges NSERC and the Canada Foundation of Innovation (CFI) for the Canada Research Chair Award in Materials and Environmental Chemistry作者联系地址:湖首大学化学系, 加拿大, 安大略 P7B 5E1Author's Address: Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada通讯作者E-mail:[email protected]

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