一步溶剂热法合成Bi_(2)S_(3)/BiOBr多级异质结及其增强可见光光催化去除RhB的研究

One-step Solvothermal Synthesis of Bi_(2)S_(3)/BiOBr Hierarchical Heterojunction for Enhanced Visible-light Photocatalytic RhB Removal

近年来,随着工业的高速发展,环境污染问题日益加剧。光催化作为一种节能环保、应用前景广阔的技术,已成为环境污染治理领域的研究热点。早期光催化剂以TiO_(2)为主,但TiO_(2)的活性只有在紫外光照下才能被激发,因此国内外逐渐发展了众多可见光可激发的光催化剂。其中,溴氧化铋(BiOBr)作为一种新型的层状结构光催化剂,因具有独特的光学性质和特殊的电子结构,近年来受到越来越多的关注。然而,纯BiOBr在可见光范围内的吸收能力并不理想,这极大地限制了它的实际应用。目前,与其他具有优异可见光吸收能力的半导体耦合是提升BiOBr光催化活性的一种有效方法。本研究首次采用硫化钠作为硫源,通过简单的一步溶剂热法合成了二元三维Bi_(2)S_(3)/BiOBr多级异质结球状光催化剂。使用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)等手段表征了样品的结构与形貌。结构测试分析表明纳米花状的Bi_(2)S_(3)/BiOBr三维球体被成功制备,且二组分间形成了紧密的界面连接。对罗丹明B(RhB)的可见光光催化降解试验结果表明Bi_(2)S_(3)/BiOBr复合材料的催化性能高度依赖于Bi_(2)S_(3)的含量。12.5%-Bi_(2)S_(3)/BiOBr样品表现出对RhB最大去除能力。对降解效率进行了准一级动力学研究,拟合结果显示12.5%-Bi_(2)S_(3)/BiOBr的降解效率分别是纯BiOBr和纯Bi_(2)S_(3)的4.2倍和39.6倍。采用光致发光测试、光电流测试、电化学阻抗测试以及紫外可见光漫反射测试对降解机理进行了研究,Bi_(2)S_(3)/BiOBr复合材料光催化性能增强的主要原因是组分间形成了有效异质结结构,使得载流子分离效率提高,可见光吸收范围扩大。活性物种的淬灭实验表明RhB的降解主要来自空穴的氧化作用,其次是超氧基自由基的作用。通过能带计算及实验分析发现超氧自由基的形成与染料敏化有关。重复使用试验研究表明经多次循环降解后12.5%-Bi_(2)S_(3)/BiOBr样品仍表现出良好的稳定性和可重复使用性。因此,Bi_(2)S_(3)/BiOBr光催化剂还有望用于降解其他类型的有机污染物,在废水净化和环境修复领域有着潜在应用。

In recent years,with the rapid development of industry,the problem of environmental pollution has become increasingly aggravated.Photocatalysis,as an energy-saving and environment-friendly technology with broad application prospects,has become a research hotspot in the field of environmental pollution treatment.In the beginning,the photocatalysts were mainly studied on TiO_(2),but the activity of TiO_(2) can only be excited under UV illumination,so numerous visible light excitable photocatalysts were gradually developed at home and abroad.Among them,bismuth bromide oxide(BiOBr)has been regarded as an innovative photocatalyst due to its unique optical properties and special electronic structure.However,the short wavelength range of visible light absorption of pure BiOBr is the bottleneck of its practical application.Nowadays,coupling with other semiconductors possessing excellent visible light absorption capacity has been considered an effective method to improve the photocatalytic performance of BiOBr phototalysts.In this study,an efficient binary three-dimensional spherical Bi_(2)S_(3)/BiOBr hierarchical heterostructure photocatalyst composed of lamellar BiOBr and rod-like Bi_(2)S_(3) was constructed via a one-step solvothermal route.The obtained samples with different Bi_(2)S_(3) contents were characterized by X-ray powder diffraction,scanning electron microscopy,high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy.The structural analysis showed that the nano-flower-like Bi_(2)S_(3)/BiOBr three-dimensional spheres were successfully prepared and a tight interfacial connection was formed between the two components.The photocatalytic tests revealed that the catalytic properties of the composites were highly dependent on the Bi_(2)S_(3) content.Moreover,the 12.5%-Bi_(2)S_(3)/BiOBr composite exhibited the maximum activity for RhB degradation under visible light illumination,which was 4.2 times and 39.6 times higher than that of the BiOBr and Bi_(2)S_(3) components,respectively.The mechanism of enhanced photocatalytic activity was proposed based on photoluminescence analysis,photocurrent measurements,electrochemical impedance and UV diffuse reflectance spectroscopy.The enhanced photocatalytic performance of the Bi_(2)S_(3)/BiOBr composites was mainly attributed to the formation of an effective heterojunction structure between the components,which led to an increase in carrier separation efficiency and an expansion of the visible light absorption range.The trapping experiments of active species showed that the degradation of RhB was mainly from the oxidation of cavities,followed by the action of superoxide radicals.The formation of superoxide radicals was found to be related to dye sensitization by energy band calculations and experimental analysis.The reusability test study showed that the 12.5%-Bi_(2)S_(3)/BiOBr samples still showed good stability and reusability after multiple cycles of degradation.Therefore,RhB removal by Bi_(2)S_(3)/BiOBr indicates the potential of the as-prepared composite to degrade other types of organic compounds for wastewater purification and environmental remediation applications.