摘要
基于修饰的高分子网络凝胶法,通过简单的工艺流程制备出高效的ZnO/TiO_(2)纳米复合光催化剂,并调节复合物中成分的比例优化了光催化剂的性能。研究结果发现,微量的TiO_(2)添加和高浓度TiO_(2)复合均改善了颗粒状ZnO纳米光催化剂的催化活性,它们在模拟太阳光照下对甲基橙的降解效率更高,增强的性能分别归因于表面氧空位缺陷增多和多元异质结结构增强的界面电荷转移引起的高光生电子-空穴分离率。此外,ZnO和TiO_(2)对亚甲基蓝和甲基橙的光催化降解存在一定的选择性,这与催化剂表面带电性和污染物分子的离子性有关。抑制剂实验表明催化剂表面形成的活性物种羟基自由基、超氧自由基和光生空穴均参与亚甲基蓝和甲基橙的降解反应,在甲基橙的降解反应中超氧自由基起主导作用。循环实验证实所制备的光催化剂具有较高的稳定性。为探索可能的实际应用,进一步研究了催化剂用量和污染物溶液的pH值对催化剂的光催化性能的影响。结果表明,催化剂用量的增加为污染物分子和入射光提供了更多的活性位点,提高了污染物降解效率;因碱性溶液含高浓度强氧化性的羟基自由基,催化剂在碱性环境中光降解污染物的效率明显提高。
The composite nanostructures composed of different semiconductors endow them with the high separation rate of photogenerated electrons and holes through the charge transfer effect at the heterojunction interface,to achieve high performances of the photocatalysts.Based on such nanostructure,multiple nanoheterostructure photocatalysts has become a research hotspot in the field of photocatalysis.Among them,ZnO/TiO_(2) nanocomposite material exhibits excellent photocatalytic performances,while the existing synthesis process is complex and limits its industrial application in photocatalysis.For this reason,based on the modified polymer network gel method,we prepared a highly efficient ZnO/TiO_(2) nanocomposite photocatalyst by the simply designed process routes,and adjusted the ratio of the components in the composites to optimize the photocatalytic performance.The TiO_(2) content was calculated according to the molar ratio of Ti/(Ti+Zn),which are 0.2 mol/mol,2 mol/mol,10 mol/mol,25 mol/mol and 50 mol/mol respectively.The corresponding samples were labeled as ZT0.002,ZT0.02,ZT0.1,ZT0.25 and ZT0.5.The phase compositions,morphology features,microstructures,surface chemical states,and optical and electrical properties of the catalysts were characterized by X-ray diffraction,scanning electron microscope,transmission electron microscope,inductively coupled plasma mass spectrum,X-ray photoelectron spectroscopy,electron paramagnetic resonance spectrum,ultraviolet and visible spectrophotometry and steady-state surface photovoltage spectra.Also,we studied the photocatalytic degradation characteristics of the catalysts toward methylene blue and methyl orange under simulated sunlight irradiation.Correspondingly,the mechanism about the change in the composition of the composite photocatalyst causing the change in its catalytic activity was proposed.The results of the study indicated that the addition of a small amount of TiO_(2) and compositing with the high-concentration TiO_(2) both improved the catalytic activity of the granular ZnO nanophotocatalyst.Under simulated sunlight irradiation,they possess the higher degradation efficiencies to methyl orange,and the enhanced performances are respectively attributed to the enhanced charge carrier separation efficiencies caused by the increased surface oxygen vacancy defects and the enhanced interfacial charge transfer in the multi-heterojunction structure.To be specific,the phase composition and microstructure analysis indicated that the only hexagonal wurtzite phase ZnO is observed in ZT0.002,while there is a multi-heterojunction structure composed of hexagonal wurtzite phase ZnO,anatase phase TiO_(2) and cubic phase Zn_(2)TiO_(4) for the samples composited with the high-concentration TiO_(2).The morphology feature analysis indicated that ZT0.002 and ZT0.5 exhibit less particle agglomeration,uniform particle size distribution and larger average particle size compared with other samples.Although the large average particle size results in a small specific surface area,less particle agglomeration reduces the recombination of electrons and holes migrating to the interfaces between the crystals.The surface chemical state and defect situation analysis indicated that ZT0.002 has a higher concentration of surface oxygen vacancy defects than that of ZnO,which is caused by the regulation of the nucleation,crystallization and crystal growth process of ZnO by a trace amount of TiO_(2).The increased surface oxygen vacancies promote the separation of photogenerated carriers and increase the active adsorption sites for the reactant molecules.Likewise,the photogenerated carrier separation efficiency is enhanced by the formation of the multi-heterojunction structure among ZnO,TiO_(2) and Zn_(2)TiO_(4).In addition,ZnO and TiO_(2) showed a certain selectivity for the photocatalytic degradation of methylene blue and methyl orange,which is related to the electrification of the catalyst surface and the onicity of pollutant molecules.Radical scavenger experiments showed that the surface active species such as hydroxyl radicals and superoxide radical as well as photogenerated holes participate in the degradation reactions of methylene blue and methyl orange on the catalyst surfaces,and superoxide radical plays a dominant role in the degradation of methyl orange.Cycling experiments evidenced the high stability of the as-prepared photocatalyst.For practical applications,the influences of the catalyst dosage and pH value of the pollutant solution on the photocatalytic performance of the catalyst have also been studied.
作者
潘泽美
张秋平
宋曼
袁欢
刘禹彤
苏元捷
徐明
PAN Zemei;ZHANG Qiuping;SONG Man;YUAN Huan;LIU Yutong;SU Yuanjie;XU Ming(College of Electronic Information&Key Lab of Information Materials of Sichuan Province,Southwest Minzu University,Chengdu 610041,China;State Key Laboratory of Electronic Thin Films and Integrated Devices,School of Optoelectronic Science and Engineering,University of Electronic Science and Technology of China,Chengdu 610054,China;Laboratory of Superconductivity and Material Applications,College of Physics and Energy,Fujian Normal University,Fuzhou 350117,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2022年第4期399-416,共18页
Acta Photonica Sinica
基金
国家自然科学基金(No.62074027)
四川省科技厅应用基础研究重点项目(No.2017JY0349)
中国博士后科学基金面上项目(No.2021M700688)。
