Gadisa Bekelcha Tesfaye, Kassahun Shimelis K, Appiah-Ntiamoah Richard, Kim Hern
Department of Energy Science and Technology, Myongji University, Yongin, Gyeonggi-do 17058, Republic of Korea.
School of Chemical and Bio Engineering, Addis Ababa Institute of Technology, Addis Ababa, Ethiopia.
J Colloid Interface Sci. 2020 Jun 15;570:251-263. doi: 10.1016/j.jcis.2020.03.002. Epub 2020 Mar 3.
Maximizing anion (carbon) doping is thought to increase the charge carrier density in ZnO and other semiconductor metal oxide photocatalysts. It also enhances the photocatalytic activity of ZnO nanostructures by imparting visible light responsiveness. However, the effect of the carbon source on the doping efficiency, and in turn on the photocatalytic activity of ZnO nanostructures has been overlooked thus far. In this study one dimensional (1D) ZnO-Carbon composite nanofibers were prepared from different polymer (polyacrylonitrile, polystyrene, polyvinylpyrrolidone) precursor solutions and the C-doping efficiency and its effect on the photocatalytic activity were studied. The prepared nanofiber photocatalysts were characterized by XRD, XPS, FE-SEM, BET, TGA, FT-IR, photoelectrochemical and optical analyses techniques. Based on the thermal degradation profile of the polymer sources, the C-doping efficiencies varied among the samples prepared and so does their photocatalytic activity. Caffeine molecule was selected as a model emerging contaminant and its photodegradation was analyzed in the presence of the as-prepared photocatalysts. Upon the C-doping, new energy level was introduced within the bandgap of ZnO that lowers its bandgap energy by 0.35 eV. Additionally, the charge carrier density of ZnO increased and the flat band potential showed positive shift. These, together with the 1D nature of the photocatalysts, enhanced the photocatalytic activity of pristine ZnO by ~58% and 2.8 folds faster kinetics. Mechanistic study showed that hydroxyl radicals were the most active reactive species responsible for the caffeine molecule degradation. This study underscores that the photocatalytic activity of ZnO for the degradation of environmental pollutants can be maximized by C-doping through careful selection of the carbon source.
人们认为，使阴离子（碳）掺杂最大化可提高氧化锌（ZnO）及其他半导体金属氧化物光催化剂中的载流子密度。它还通过赋予可见光响应性来增强ZnO纳米结构的光催化活性。然而，迄今为止，碳源对掺杂效率进而对ZnO纳米结构光催化活性的影响一直被忽视。在本研究中，由不同的聚合物（聚丙烯腈、聚苯乙烯、聚乙烯吡咯烷酮）前驱体溶液制备了一维（1D）ZnO-碳复合纳米纤维，并研究了碳掺杂效率及其对光催化活性的影响。通过X射线衍射（XRD）、X射线光电子能谱（XPS）、场发射扫描电子显微镜（FE-SEM）、比表面积分析仪（BET）、热重分析仪（TGA）、傅里叶变换红外光谱仪（FT-IR）、光电化学和光学分析技术对制备的纳米纤维光催化剂进行了表征。基于聚合物源的热降解曲线，所制备样品的碳掺杂效率各不相同，其光催化活性也是如此。选择咖啡因分子作为典型的新兴污染物，并在制备的光催化剂存在下分析其光降解情况。碳掺杂后，在ZnO的带隙内引入了新的能级，使其带隙能量降低了0.35电子伏特。此外，ZnO的载流子密度增加，平带电位出现正移。这些因素与光催化剂的一维特性一起，使原始ZnO的光催化活性提高了约58%，动力学速度加快了2.8倍。机理研究表明，羟基自由基是导致咖啡因分子降解的最活跃的活性物种。本研究强调，通过仔细选择碳源进行碳掺杂，可以使ZnO对环境污染物降解的光催化活性最大化。
