An efficient and stable narrow bandgap carbon dot-brookite composite over other CD-TiO2 polymorphs in rhodamine B degradation under LED light
An efficient and stable narrow bandgap carbon dot-brookite composite over other CD-TiO2 polymorphs in rhodamine B degradation under LED light
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DOI：
10.1016/j.ceramint.2019.04.121
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发表时间：
2019-08-01
影响因子：
5.2
通讯作者：
Ofomaja, Augustine E.
中科院分区：
文献类型：
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作者：
Oseghe, Ekemena O.;Msagati, Titus A. M.;Ofomaja, Augustine E.
将松树皮中的碳点（CD）负载到三种多晶型TiO 2（金红石型、金红石型和板钛矿型，分别简称为Ana、Rut和Brk）上，研究了它们在可见光LED下对罗丹明B（RhB）的光催化降解性能。采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线粉末衍射（XRD）、N2吸附等温线、傅里叶变换红外光谱（FT-IR）、紫外漫反射光谱（UV-DRS）和X射线光电子能谱（XPS）等手段对材料进行了表征。X-射线衍射结果表明，成功地制备了不同的纯原始多晶型物及其复合物，其中Rut和CD-Rut复合物的最大晶粒尺寸分别为23.06和21.64 nm。材料的N2吸附等温线显示Ana、Brk及其复合材料的吸附等温线均为IV型吸附等温线，且具有H系滞后回线，表明它们是介孔材料。Rut和CD-Rut所表现出的等温线表明它们是无孔的。然而，它们的孔径分布（PSD）表明，材料具有中孔，这可能是由于颗粒聚集而导致的颗粒间空隙。光催化降解实验的结果表明，材料表现为以下顺序：CD-Brk > Brk > CD-Ana > CD-Rut > Rut > Ana，相应的RhB去除百分比分别为99.91%、76.78%、36.28%、27.50%、22.65%和12%。CD-Brk和Brk的优异性能归因于其2.00 eV的窄带隙能量，使其在可见光LED光下更活跃。CD-Brk的性能优于Brk，因为它具有更多的表面活性位点，这是由于其相对较高的表面积。从降解机制来看，CD-Brk经过4个周期的降解后仍保持稳定，表明超氧阴离子自由基（O-2（中心点-））在降解过程中起主要作用。
Carbon dot (CD) obtained from pine bark was loaded on three TiO2 polymorphs (anatase, rutile, and brookite abbreviated in this study as Ana, Rut, and Brk respectively) to evaluate their photocatalytic performance in rhodamine B (RhB) degradation under visible-LED light. The materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray powder diffraction (XRD), N-2 sorption isotherm, and Fourier transform infrared (FT-IR), UV-diffused reflectance spectroscopy (UV-DRS), and x-ray photoelectron spectroscopy (XPS). The x-ray result shows that the different pure pristine polymorphs and their composites were successfully prepared with Rut and CD-Rut composite having the highest crystallite size of 23.06 and 21.64 nm respectively. The N-2 sorption isotherm of the materials shows Ana, Brk and their composite exhibited type IV isotherm with H series hysteresis loop, which implies that they are mesoporous materials. The isotherm exhibited by Rut and CD-Rut suggests that they are non-porous. However, their pore size distribution (PSD) shows that the materials possess mesopores that may have resulted from interparticle voids due to particle aggregation. Results from the photocatalytic degradation experiments showed that the materials performed in the following order CD-Brk > Brk > CD-Ana > CD-Rut > Rut > Ana with a corresponding percentage RhB removal of 99.91, 76.78, 36.28, 27.50, 22.65, and 12% respectively. The excellent performance of CD-Brk and Brk over the others is attributed to their narrow bandgap energy of 2.00 eV making them more active under the visible-LED light. CD-Brk performed better than Brk because it possesses more surface-active sites resulting from its relatively higher surface area. In terms of degradation mechanism, CD-Brk which was stable after 4 cycles of degradation, showed that superoxide anion radical (O-2(center dot-)) played major role in the degradation process.