Khan Ayesha, Goepel Michael, Lisowski Wojciech, Łomot Dariusz, Lisovytskiy Dmytro, Mazurkiewicz-Pawlicka Marta, Gläser Roger, Colmenares Juan Carlos
Institute of Physical Chemistry, Polish Academy of Sciences Warsaw 01-224 Poland
Institute of Chemical Technology, Leipzig University Leipzig 04103 Germany
RSC Adv. 2021 Oct 28;11(55):34996-35010. doi: 10.1039/d1ra06500a. eCollection 2021 Oct 25.
Developing functional materials from biomass is a significant research subject due to its unique structure, abundant availability, biodegradability and low cost. A series of chitosan-lignin (CL) composites were prepared through a hydrothermal method by varying the weight ratio of chitosan and lignin. Subsequently, these CL composites were combined with titania (T) to form a nanocomposite (T/CL) using sol-gel and hydrothermal based methods. T/CL nanocomposites exhibited improved photocatalytic performance in comparison with sol-gel and hydrothermally prepared pristine titania (SGH-TiO), towards the selective oxidation of benzyl alcohol (BnOH) to benzaldehyde (Bnald) under UV (375 nm) and visible light (515 nm). More specifically, the 75T/CL(25 : 75) nanocomposite (a representative photocatalyst from the 75T/CL nanocomposite series) showed very high selectivity (94%) towards Bnald at 55% BnOH conversion under UV light. Whereas, SGH-TiO titania exhibited much lower (68%) selectivity for Bnald at similar BnOH conversion. Moreover, the 75T/CL(25 : 75) nanocomposite also showed excellent Bnald selectivity (100%) at moderate BnOH conversion (19%) under visible light. Whereas, SGH-TiO did not show any activity for BnOH oxidation under visible light. XPS studies suggest that the visible light activity of the 75T/CL(25 : 75) nanocomposite is possibly related to the doping of nitrogen into titania from chitosan. However, according to UV-visible-DRS results, no direct evidence pertaining to the decrease in band-gap energy of titania was found upon coupling with the CL composite and the visible light activity was attributed to N-doping of titania. Overall, it was found that T/CL nanocomposites enhanced the photocatalytic performance of titania improved light harvesting and higher selectivity through mediation of active radical species.
利用生物质开发功能材料是一个重要的研究课题，因为其具有独特的结构、丰富的可获取性、生物可降解性和低成本。通过水热法，改变壳聚糖和木质素的重量比，制备了一系列壳聚糖-木质素（CL）复合材料。随后，采用基于溶胶-凝胶和水热法，将这些CL复合材料与二氧化钛（T）结合，形成纳米复合材料（T/CL）。与溶胶-凝胶法和水热法制备的原始二氧化钛（SGH-TiO）相比，T/CL纳米复合材料在紫外光（375 nm）和可见光（515 nm）下对苯甲醇（BnOH）选择性氧化为苯甲醛（Bnald）表现出更高的光催化性能。更具体地说，75T/CL(25 : 75)纳米复合材料（75T/CL纳米复合材料系列中的一种代表性光催化剂）在紫外光下，当BnOH转化率为55%时，对Bnald表现出非常高的选择性（94%）。而SGH-TiO二氧化钛在类似的BnOH转化率下，对Bnald的选择性要低得多（68%）。此外，75T/CL(25 : 75)纳米复合材料在可见光下，当BnOH转化率适中（19%）时，也表现出优异的Bnald选择性（100%）。而SGH-TiO在可见光下对BnOH氧化没有任何活性。XPS研究表明，75T/CL(25 : 75)纳米复合材料的可见光活性可能与壳聚糖中氮掺杂到二氧化钛中有关。然而，根据紫外-可见-漫反射光谱（UV-visible-DRS）结果，未发现与二氧化钛带隙能量降低相关的直接证据，可见光活性归因于二氧化钛的氮掺杂。总体而言，发现T/CL纳米复合材料通过活性自由基物种的介导，增强了二氧化钛的光催化性能，改善了光捕获并提高了选择性。
