构建2D-2D TiO_2纳米片/层状WS_2异质结用以增强可见光响应光催化活性（英文）
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摘要
自Fujishima等首次报道以来, TiO_2作为一种重要的光催化剂引起了人们的广泛关注.迄今为止,研究人员已经开发出了各种形貌的具有不同晶型结构的TiO_2,并用于光催化降解有机污染物.然而, TiO_2的宽禁带(3.2 eV)使其难以被可见光激活,导致对太阳光的利用效率低下.而且,在光催化反应中,低的量子效率无法满足实际应用.因此,开发具有可见光响应的高催化活性的TiO_2基催化剂具有重要意义.集成复合材料、纳米材料和界面的优势构建纳米复合材料已成为提高TiO_2光催化活性的重要策略. WS_2具有典型的类石墨烯层状结构和窄的带隙(1.35 eV),且其导带高于TiO_2的导带,适合作为助催化剂修饰TiO_2,使其具备可见光响应光催化活性.本文采用一步水热法,以二维(2D)TiO_2纳米片作基质材料,直接在其表面原位生长WS_2层,制得了2D-2D TiO_2纳米片/层状WS_2(TNS/WS_2)异质结. XRD及Raman结果表明,层状WS_2与TiO_2纳米片紧密结合在一起,且两者之间形成了W=O键.TEM结果显示,层状WS_2以面-面堆叠方式均匀地包覆在TiO_2纳米片表面,包覆层数约为4层.光催化性能测试结果表明,可见光照射下, TNS/WS_2异质结对RhB的光催化降解能力高于原始TiO_2纳米片和层状WS_2,光催化活性得到明显增强.紫外可见光谱试验结果显示,层状WS_2的引入极大地增强了异质结的光吸收性能. PL光谱测试表明, TNS/WS_2异质结具有更高效的载流子分离效率.为了进一步证实是光吸收性能的提升还是载流子分离效率的增强对光催化性能提起其主要作用,本文还研究了3D-2D TiO_2空心微球/层状WS_2(THS/WS_2)复合材料.结果表明, TNS/WS_2异质结比THS/WS_2复合材料具有更高效的光生电子和空穴的分离能力.从而证明了TiO_2纳米片与层状WS_2之间完美的2D-2D纳米界面和紧密的界面结合,显著增加了载流子分离效率,因此光催化活性得到明显提高.为了研究TNS/WS_2异质结光催化剂的光催化机理,采用重铬酸钾、草酸铵、叔丁醇和对苯醌作自由基猝灭剂进行了自由基捕捉剂实验.结果表明,空穴在RhB降解过程中起主要作用,超氧自由基起次要作用.基于自由基猝灭实验结果和带隙结构分析,提出了TNS/WS_2异质结对RhB的光催化机理为双转移光催化机理.可见,界面异质结工程化可能是制备高效和环境稳定的光催化剂的新思路
Constructing nanocomposites that combine the advantages of composite materials, nanomaterials,and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO_2. In this study, 2 D-2 D TiO_2 nanosheet/layered WS-2(TNS/WS_2) heterojunctions were prepared via a hydrothermal method. The structure and morphology of the photocatalysts were systematically characterized. Layered WS_2(～4 layers) was wrapped on the surface of TiO_2 nanosheets with a plate-to-plate stacked structure and connected with each other by W=O bonds. The as-prepared TNS/WS_2 heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible-light irradiation, than pristine TiO_2 nanosheets and layered WS_2. The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency, which originated from the perfect 2 D-2 D nanointerfaces and intimate interfacial contacts between TiO_2 nanosheets and layered WS_2. Based on experimental results, a double-transfer photocatalytic mechanism for the TNS/WS_2 heterojunctions was proposed and discussed. This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.
Constructing nanocomposites that combine the advantages of composite materials, nanomaterials,and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO_2. In this study, 2 D-2 D TiO_2 nanosheet/layered WS-2(TNS/WS_2) heterojunctions were prepared via a hydrothermal method. The structure and morphology of the photocatalysts were systematically characterized. Layered WS_2(～4 layers) was wrapped on the surface of TiO_2 nanosheets with a plate-to-plate stacked structure and connected with each other by W=O bonds. The as-prepared TNS/WS_2 heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible-light irradiation, than pristine TiO_2 nanosheets and layered WS_2. The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency, which originated from the perfect 2 D-2 D nanointerfaces and intimate interfacial contacts between TiO_2 nanosheets and layered WS_2. Based on experimental results, a double-transfer photocatalytic mechanism for the TNS/WS_2 heterojunctions was proposed and discussed. This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.
引文
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