【作者】 黄宏妙；

【导师】 林翠梧；

【作者基本信息】 广西大学 ， 应用化学， 2022， 博士

【摘要】 水资源是不可再生资源,随着工业和农业的发展,水资源的污染已经成为一个严重的全球性问题。半导体光催化技术是一种环境友好的绿色水处理技术,特别适于水环境中微污染物的有效治理。由于TiO₂具有良好的化学稳定性和较高的光催化性能,已被广泛用于水污染处理。但是TiO₂在使用过程中仍然存在可见光响应差、光生电荷分离效率低和分离回收困难等不足。针对以上不足,本文采用表面修饰和缺陷调控的策略构建新型TiO₂基复合材料;通过降解罗丹明B（Rh B）、盐酸四环素（TC）、17α-乙炔基雌二醇（EE2）和亚硝酸盐（NO₂^-）等多种污染物评估所制备材料的可见光催化性能;结合SEM、TEM、XPS、EPR、UV-vis DRS、PL、EIS和UPLC-MS等多种表征手段,分别研究了复合材料的形貌、表面缺陷、能带结构和电子转移与光催化活性之间的构效关系,探讨光催化活性增强机制、反应活性物质及污染物降解机理和路径,为设计和开发多功能、高效、易于回收的TiO₂基复合材料提供理论和实验依据。主要的研究内容和结果如下:（1）针对TiO₂可见光响应差、光生电荷分离效率低的问题,采用表面修饰策略,以油酸为溶剂和碳源、钛酸丁酯为钛源,溶剂热法成功制备C修饰TiO₂复合材料（TiO₂/C）。系列表征分析结果表明,C物种通过与钛离子双齿配位修饰在TiO₂表面,有效抑制了TiO₂晶粒的过度生长和团聚,增大了比表面积;拓宽了可见光吸收范围,使TiO₂/C的可见光吸收边缘值比自制纯TiO₂增大了10nm,带隙能降低了0.09eV;此外,还显著提高了光生载流子的分离和转移效率。以光催化降解Rh B为探针反应,在可见光照射120min后,TiO₂/C对Rh B的降解率能到达81%,降解速率常数（k）为0.0110min^-1,分别是自制纯TiO₂和商品级TiO₂（P25）的3.24和5.00倍。修饰在TiO₂表面的碳质层,增强了复合材料的稳定性,使复合材料经过5次循环实验均能保持稳定的光催化活性。（2）为了进一步提高TiO₂/C光催化活性,采用缺陷调控策略,在上一章C修饰的基础上,以HCl为调控剂和掺杂剂,一锅溶剂热法可控合成具有三维分级结构的C修饰和Cl掺杂的TiO₂复合材料（Cl-TiO₂/C）。系列表征分析结果表明,HCl的加入量可以调控Cl-TiO₂/C的形貌,当HCl与TBOT的体积比为0.4时为海胆状微球结构,该形貌演变遵循成核、核生长、溶解和重结晶的生长机制;同时Cl进入TiO₂晶格掺杂取代了O原子,引入了氧空位（OVs）缺陷,OVs浓度可由Cl掺杂量调控。以光催化降解Rh B为探针反应,在可见光照射120min后,0.4Cl-TiO₂/C对Rh B的降解率能达到95%,相应的k值为0.0221 min^-1,分别是单一Cl掺杂（Cl-TiO₂）和单一C修饰（TiO₂/C）复合材料的3.75和2.01倍,说明由Cl掺杂引入的OVs和C修饰存在协同作用,共同提高复合材料的光催化能力;0.4Cl-TiO₂/C经过5次光催化循环实验后,结构形貌和催化活性均未发生明显变化,这归因于C修饰层可作为Cl掺杂和OVs的有效保护层,增强了复合材料的稳定性。（3）为了进一步提高Cl-TiO₂/C复合材料的稳定性和便于回收,本章采用载体负载策略,在上一章的基础上,采用具有一定活性基团的多孔炭泡沫（CF）作为硬模板剂和载体,一锅溶剂热法原位生成CF负载C修饰、Cl掺杂的TiO₂复合材料（Cl-TiO₂/C@CF）。系列表征分析结果表明,Cl-TiO₂/C海胆状微球以Ti-O-C和Ti-OCO化学键的形式成功锚定在CF表面和孔道内,并呈单层均匀分布,在CF和Cl-TiO₂/C的协同作用下,带隙能从2.75eV下降到了2.13eV,光量子产率有效增强;导带电位从-0.30下降到-0.86,有效提高了Cl-TiO₂/C@CF的光催化还原能力;光生电子从TiO₂导带迁移到CF表面的速率进一步加快,促进光生电子-空穴对的快速分离;可见光激发下Cl-TiO₂/C@CF比Cl-TiO₂/C具有更强的光生电子和·O₂^–的产生能力,说明其光催化氧化和还原能均得到了增强。（4）基于上一章制备的Cl-TiO₂/C@CF复合材料同时具有强光催化氧化和还原能力,采用EE2和NO₂^-为目标模拟物,系统地考察其同时光催化氧化EE2和光催化还原NO₂^-的可行性。研究结果表明,可见光照射120min后,最佳pH条件下,Cl-TiO₂/C@CF对在单一体系中的NO₂^-和EE2的去除率分别能达到94.3%和88.2%,相应的光催化速率常数k分别是Cl-TiO₂/C的6.63和2.19倍。说明CF的引入,有效增强了复合材料的光催化氧化和还原能力。在NO₂^-和EE2共存体系中（pH=6）,可见光照射120min后,Cl-TiO₂/C@CF对NO₂^-和EE2的去除率分别能达到100%和94.5%,相应的k值分别是单一体系中的1.90和1.44倍;而且Cl-TiO₂/C@CF光催化还原NO₂^-为N₂的选择率为82.4%,显著高于单一体系中的64.5%,说明在共存体系中Cl-TiO₂/C@CF对NO₂^-和EE2的光催化反应存在协同促进作用,EE2的存在不仅能有效提高NO₂^-的去除率还能提高N₂的选择性;共存体系中,Cl-TiO₂/C@CF重复使用5次后,其结构组成和催化活性均未发生明显变化,说明Cl-TiO₂/C@CF是一种光催化氧化和还原能力俱强、结构稳定、回收方便的可再生光催化剂。该研究为废水处理提供了一个光降解与光还原相结合的新途径。（5）为了提高Cl-TiO₂/C复合材料对难降解有机污染物的光催化降解效果,本章在第三章的基础上采用金属和非金属双掺杂策略,制备了Zr、Cl共掺杂和C修饰的TiO₂基复合材料（Zr/Cl-TiO₂/C）。系列表征分析结果表明,Zr⁴⁺掺杂取代了TiO₂晶格中的Ti⁴⁺,不仅引入了杂质能级,构建TiO₂的杂原子取代缺陷,同时还提高了氧空位缺陷的浓度。两种缺陷态的协同作用显著缩小了复合材料的禁带宽度,进一步促进了光生载流子的分离。此外,Zr⁴⁺掺杂有效促进了催化剂表面羟基化,有利于强氧化性的·OH自由基的产生,提高了复合材料的光催化氧化能力。以TC为目标模拟物,可见光照射120min后,Zr/Cl-TiO₂/C对TC的降解率能到达91%,降解速率常数k值为0.0183 min^-1,是Cl-TiO₂/C速率常数的2.85倍。光催化循环5次以后,仍能保持稳定的结构组成和催化活性,具有良好的重复使用性。更多还原

【Abstract】 Water is non-renewable resources.The pollution of water resources has become a serious global problem with the developments of industry and agriculture.Heterogeneous photocatalysis based on semiconductors is a green and environmentally friendly advanced oxidation technique,which is especially suitable for the effective treatment of micro-pollutants in water.Owing to high chemical stability and excellent photocatalytic activity,TiO₂ has been widely used for water pollution treatment.However,TiO₂ still suffers from poor visible light response,low separation efficiency of photogenerated carriers and difficulties in separation and recovery in its actual application.To address these shortcomings,this research proposes a strategy for constructing new TiO₂-based composites by surface modification and defect modulation.The visible photocatalytic activities of as-prepared materials were evaluated by degrading various pollutants such as rhodamine B（Rh B）,tetracycline hydrochloride（TC）,and 17α-ethynylestradiol（EE2）and nitrite（NO₂^-）.Meanwhile,The relationship between photocatalytic activity and composites’characteristc including morphology,surface defects,energy band structure and electron transfer were systematically investigated by various characterization methods such as SEM,TEM,XPS,EPR,UV-vis DRS,PL,EIS and UPLC-MS,respectively.And the enhancement photocatalytic activity mechanism,reactive substances,pollutant degradation mechanisms and pathways were also explored.This research can provide theoretical and experimental basis for the design and development of TiO₂-based composites with multifunction,high photocatalytic activity and convenient recycling.The main research contents and results are as follows:（1）To address the problems of poor visible light response and low photogenerated charge separation efficiency of TiO₂,the TiO₂-based composite with C modification（TiO₂/C）was successfully prepared by solvent-thermal method using oleic acid as solvent and carbon source,butyl titanate as titanium source.The series characterization results showed that C species were modified on the TiO₂ surface by double-dentate coordination with titanium ions.The C species modified on the TiO₂ surface could effectively inhibite the overgrowth and agglomeration of TiO₂ grains,increase the specific surface area,and broaden the visible light absorption range.Compared to the pure TiO₂,the visible light absorption edge value of TiO₂/C was increased by 10 nm,the band gap energy was reduced by 0.09 eV,and the separation and transfer efficiency of photogenerated carriers were also significantly improved.To test the photocatalytic activity of TiO₂/C,rhodamine B（Rh B）was selected as a simulated organic contaminant,and the degradation rate of Rh B could reach81%after 120 min of visible light irradiation,degradation rate constant（k）was 0.0110 min^-1,which was 3.24 and 5.00 times higher than that of pure TiO₂and commercial TiO₂（P25）,respectively.The carbonaceous layer modified on the surface of TiO₂ can enhance the stability of the composites,leading to stable photocatalytic activity after five cycles of photocatalytic experiments.（2）In order to further improve the photocatalytic activity of TiO₂/C,on the basis of the C modification in the previous chapter,a defect modulation strategy was employed for the controlled synthesis of C-modified and Cl-doped TiO₂composites（Cl-TiO₂/C）with a three-dimensional hierarchical structure by a one^-pot solvent-thermal method using HCl as the modulator and dopant.The results of series characterization analysis showed that the addition of HCl could controlled the morphologies of Cl-TiO₂/C composites.When the volume ratio of HCl to TBOT was 0.4,a sea urchin-like microsphere structure could be formed,and the growth of this morphology was governed by a mechanism of nucleation and nuclei growth–dissolution–recrystallization growth.The Cl doped and substituted of O atoms in the TiO₂ lattice,introducing oxygen vacancies（OVs）defects into the composites,and the concentration of OVs could be controlled by the amount of Cl-doping.To test the photocatalytic activity of Cl-TiO₂/C,Rh B was selected as a simulated organic contaminant.The degradation rate of Rh B by 0.4Cl-TiO₂/C could reach 95%after visible light irradiation for 120 min,and the degradation rate constant（k）was 0.0221 min^-1,which was 3.75 and 2.01times higher than that of single Cl-doped（Cl-TiO₂）and single C-modified（TiO₂/C）composites,respectively,indicating there was synergistic effect between the OVs defects and C modification,by which improved the photocatalytic activity of the composites.Furthermore,the structure and photocatalytic activity of 0.4Cl-TiO₂/C did not change significantly after five photocatalytic cycles.This was attributed to the C-modified layer which could be used as an effective protective layer for Cl doping and OVs,enhancing the stability of the composites.（3）In order to further improve the stability and facilitate the recovery of Cl-TiO₂/C composites,a carrier loading strategy was employed in this chapter based on the above chapter.Using the porous carbon foam（CF）with certain reactive groups as hard templating agent and carrier,An in-situ one-pot solvent-thermal synthesis was explored to prepare a C-modified and Cl-doped sea urchin-like TiO₂ loading on CF（Cl-TiO₂/C@CF）.The results of series characterization analysis showed that the sea urchin-like Cl-TiO₂/C microspheres were successfully anchored on the CF surface and in the pore channels with the chemical bonds of Ti-O-C and Ti-OCO,and were uniformly distributed in a monolayer.With the synergistic effect of CF and Cl-TiO₂/C in the composites,the band gap energy decreased from 2.75 eV to 2.13 eV and the conduction band potential decreased from-0.30 to-0.86 compared to Cl-TiO₂/C,effectively improving the optical quantum yield and photocatalytic reduction activity.The migration rate of photogenerated electrons from the TiO₂conduction band to CF surface was further accelerated,which promoted the rapid separation of photogenerated electron-hole pairs.Moreover,Cl-TiO₂/C@CF had stronger generation abilities of photogenerated electron and·O₂^–under visible light excitation,indicating that both the photocatalytic oxidation and reduction activities of Cl-TiO₂/C@CF were enhanced.（4）Based on the strong photocatalytic oxidation and reduction activities of the Cl-TiO₂/C@CF composite prepared in the previous chapter,the feasibility of simultaneous photocatalytic oxidation and photocatalytic reduction was systematically investigated using EE2 and NO₂^-as target simulants.The results of research showed that the removal rates of Cl-TiO₂/C@CF for NO₂^-and EE2in the single system could reach 94.3%and 88.1%,respectively,after 120 min of visible light irradiation in the optimal pH conditions,and the corresponding k values were 6.63 and 2.19 times higher than those of Cl-TiO₂/C,respectively.It indicated that the introduction of CF to Cl-TiO₂/C@CF composites effectively enhanced the photocatalytic oxidation and reduction activities of the composites.In the NO₂^-and EE2 coexistence system（pH=6）,the removal rates of NO₂^-and EE2 by Cl-TiO₂/C@CF could reach 100%and 94.5%,respectively,after 120min of visible light irradiation for,and the corresponding k values were 1.90 and1.44 times higher than those in the single system.Moreover,the selectivity of photocatalytic reduction of NO₂^-to N₂ by Cl-TiO₂/C@CF was 82.4%,which was much higher than that of 64.5%in the single system,indicating that there was a synergistic effect on the photocatalytic reaction of NO₂^-and EE2 in the coexisting system,and the presence of EE2 could not only effectively improve the conversion rate of NO₂^-but also enhance the selectivity of N₂.In the coexistence system,the structure and photocatalytic activity of Cl-TiO₂/C@CF did not change significantly after five photocatalytic cycles,indicating that Cl-TiO₂/C@CF was a renewable photocatalyst with strong photocatalytic oxidation and reduction ability,stable structure and convenient recycling.This study provides a new way to combine photodegradation and photoreduction for wastewater treatment.（5）In order to improve the photocatalytic degradation activity of Cl-TiO₂/C composites for refractory organic pollutants,the Zr,Cl co-doped and C-modified TiO₂^-based composites（Zr/Cl-TiO₂/C）were prepared in this chapter based on the double doping strategy of metals and non-metals.The results of series characterization analysis showed that Zr⁴⁺doped and substituted of Ti⁴⁺in the TiO₂ lattice,which not only introduced impurity energy levels,constructing the heteroatom substitution defects in TiO₂,but also increased the concentration of oxygen vacancy defects.With the synergistic effect of the two defect states,the forbidden band width was significantly narrowed and the separation rate of photogenerated carriers was further promoted.In addition,the Zr⁴⁺-doping effectively improved the catalyst surface hydroxylation,facilitating the generation of strongly oxidizing radicals of·OH and improving the photocatalytic oxidation activity of the composites.Using TC as the target simulant,the degradation rate of TC by Zr/Cl-TiO₂/C could reach 91%after 120min of visible light irradiation,and the corresponding k value was 0.0183 min^-1,which was 2.85 times higher than that of Cl-TiO₂/C.After five photocatalytic cycles,the structure and catalytic activity could still be maintained stably,indicating Zr/Cl-TiO₂/C had an excellent reusability.更多还原