Department of Chemistry, M S Ramaiah Institute of Technology (An Autonomous Institute Affiliated to Visvesvaraya Technological University, Belgaum), Bengaluru 560054, India; Department of Chemistry/Biochemistry, M S Ramaiah College of Arts, Science and Commerce (Affiliated to Bangalore Central University), Bangalore 560054, India.
Department of Chemistry, M S Ramaiah Institute of Technology (An Autonomous Institute Affiliated to Visvesvaraya Technological University, Belgaum), Bengaluru 560054, India.
J Colloid Interface Sci. 2022 Dec;627:956-968. doi: 10.1016/j.jcis.2022.07.100. Epub 2022 Jul 19.
Carbon dots (C-dots) developed from beetroot is used for the rational design of cadmium sulphide based heterojunction photocatalysts (C-dots@CdS) using hydrothermal technique. The crystal structure, phase, morphology and optical characteristics of the synthesised materials are determined using X-ray diffraction (XRD), High resolution transmission electron microscopy (HR-TEM), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-Visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL spectroscopy), BET adsorption, X-ray photoelectron spectroscopy (XPS) and electrochemical studies. Using C-dots@CdS catalytic system, a superior photocatalytic activity relative to the undecorated CdS is observed. Among the C-dots@CdS samples, the CdS loaded with 6 wt% of C-dots exhibited enhanced hydrogen evolution rate compared with other samples considered for the study. CdS nanospheres modified with C-dots (6 wt%) resulted in the photocatalytic hydrogen evolution rate of 1582 µmolg against 849 µmolg evolution rate obtained for CdS nanospheres within 3 h. In spite of being 0D/0D type nano-heteroarchitecture, C-dots@CdS system obtained an apparent quantum yield of 6.37 % for the catalytic dosage of 20 mg under the irradiation of visible light. CdS in the C-dots@CdS system serves as the light harvester while C-dots with discernible edges can maintain the continuous supply of photo-excited charge carriers and hence can reduce the charge-carrier recombination. Further, the photodegradation of crystal violet dye using the optimised dosage of C-dots@CdS-6 exhibited an efficiency of 97.3 % in 120 min of visible light irradiation under neutral conditions. The detailed kinetic study reveals that the mechanism of photodegradation of crystal violet dye using C-dots@CdS system can be described using pseudo-second-order kinetics. The presence of oxygen rich hydrophilic surface functionalities of C-dots, the formation of near-surface heterojunction and the suitable band structure of C-dots@CdS system leading to the optimum charge carrier separation kinetics can be attributed to the enhanced photocatalytic performance. This work offers a promising strategy to develop bio-derived C-dots based heterojunction photocatalyst to address the burgeoning energy and environmental demands.
采用水热技术，从甜菜根中开发的碳点（C-dots）用于合理设计硫化镉基异质结光催化剂（C-dots@CdS）。使用 X 射线衍射（XRD）、高分辨率透射电子显微镜（HR-TEM）、场发射扫描电子显微镜（FESEM）、能谱（EDAX）、傅里叶变换红外光谱（FTIR）、拉曼光谱、紫外-可见漫反射光谱（UV-DRS）、光致发光光谱（PL 光谱）、BET 吸附、X 射线光电子能谱（XPS）和电化学研究来确定合成材料的晶体结构、相、形态和光学特性。在 C-dots@CdS 催化体系中，观察到相对于未修饰的 CdS 的优异光催化活性。在所研究的样品中，负载 6wt%的 C-dots 的 CdS 表现出比其他样品更高的析氢速率。CdS 纳米球修饰的 C-dots（6wt%）在 3h 内产生 1582 µmolg 的光催化析氢速率，而 CdS 纳米球的析氢速率为 849 µmolg。尽管 C-dots@CdS 体系为 0D/0D 型纳米异质结构，但在可见光照射下，在 20mg 的催化剂量下，其表观量子产率为 6.37%。C-dots@CdS 体系中的 CdS 作为光收集器，而具有明显边缘的 C-dots 可以保持光生载流子的连续供应，从而减少载流子复合。此外，在中性条件下，优化剂量的 C-dots@CdS-6 对结晶紫染料的光降解效率在 120min 的可见光照射下达到 97.3%。详细的动力学研究表明，使用 C-dots@CdS 体系光降解结晶紫染料的机制可以用拟二级动力学来描述。C-dots 富氧亲水性表面官能团的存在、近表面异质结的形成以及 C-dots@CdS 体系适宜的能带结构导致最佳载流子分离动力学，可以归因于增强的光催化性能。这项工作提供了一种有前途的策略，用于开发基于生物衍生的 C-dots 的异质结光催化剂，以满足新兴的能源和环境需求。
