【作者】 陈颖；

【导师】 任召辉；

【作者基本信息】 浙江大学 ， 材料科学， 2019， 硕士

【摘要】 TiO2作为最重要的氧化物半导体材料之一,被广泛应用于环境、能源等领域。其中,锐钛矿型Ti02由于其优异的光电催化性能而受到广泛关注。设计并暴露锐钬矿Ti02晶体的高能面,如(001)面,来提高其催化活性是当前光催化材料研究的热点。如今,面临着两个重要的问题:1.锐钬矿Ti02的(001)面生长机理以及其与光催化性能的关联尚不清晰;2.Ti02基光催化材料仍受制于利用紫外光。针对上述两个关键问题,我们以(001)暴露面的锐钛矿TiO2为出发点,分别对生长机理和催化机制做出了解释,并在此基础上制备出同质结,拓宽了 TiO2材料的可见光响应范围。本论文以锐钬矿TiO2纳米片及其同质结的生长、微结构以及性能表征为核心。首先,通过水热法制备得到纯相锐钛矿TiO2纳米片,对其微结构,光解水产氢性能及生长模型进行了探究;其次,以TiO2纳米片为衬底,通过简单的热处理方法制备得到了 TiO2同质结结构,并系统地研究了热处理温度、保温时间及纳米片厚度对同质结生长的影响。本论文的主要结论如下:1.在氢氟酸环境下的水热反应中,通过调控辅助修饰剂的种类,制备出了片状和颗粒状的TiO2纳米晶。在该实验基础上,控制辅助修饰剂乙醇的添加量(2-25 mL)制备得到了厚度为2.9-13.5 nm的锐钛矿TiO2纳米片。其中,最薄的纳米片(2.9nm)可达到最高的光催化产氢性能(41.04mmol·h-1·g-1),对应的量子效率(41.6%)也最高。2.揭示了锐钛矿TiO2纳米片(001)面的生长机制:氟离子与表面的Ti空位缺陷键合,导致系统整体能量的降低,从而使得纳米片减薄。这种机制能够增大光生电子-空穴的分离效率,带来光催化性能的提高。但该键合易被碱洗液(如NaOH,KOH和LiOH等)打破,阳离子(Na+,K+和Li+等)会取代氟离子与Ti空位结合的位置,导致光生电子-空穴分离效率降低,从而使得光催化性能下降。3.用以上的锐钛矿Ti02纳米片为衬底,通过简单的热处理方法获得了锐钛矿Ti02同质结复合材料。系统地研究了热处理温度、保温时间以及纳米片厚度对同质结生长的影响。验证了温度为450 ℃,保温时间约2h,纳米片厚度薄(～4 nm)时最有助于生成有助于光催化产氢的同质结结构。其光催化产氢效率为94.37mmol.h-1·g-1;全解水效率为:产氢效率3891.49μmol.h-1·g-1,产氧效率516.43μmol·h.1·g-1,氢氧产量比为8:1。更多还原

【Abstract】 As one of the most important oxide semiconductor materials,TiO2 is widely used in the fields of environment and energy.Among them,anatase TiO2 has been widely concerned due to its excellent photocatalytic performance.To design and expose the high-energy surface of anatase TiO2 crystal is the current research hotspot of photocatalytic materials to improve its catalytic activity.There are two important problems at present:1.The growth mechanism of(001)surface of anatase TiO2 and its correlation with photocatalytic performance are still not clear;2.TiO2-based photocatalytic materials are still subject to the use of ultraviolet light.In view of the above two key problems,we took the(001)-exposed anatase TiO2 as the basis to explain the growth mechanism and catalytic mechanism respectively,and prepared TiO2 homojunction which can broaden the visible response range of TiO2 materials.In this paper,the growth,microstructure and photocatalytic performance characterization of anatase TiO2 nanosheets and its homojunction are taken as the core.Firstly,pure phase anatase TiO2 nanosheets were prepared by hydrothermal method,and its microstructure,photocataltic hydrogenation performance and growth model are studied.Secondly,the TiO2 homojunction was prepared by simple annealing method with the substrate of above nanosheets.Then the influence of annealing temperature,holding time and the thickness of nanosheets on the growth of the homogenous structure were discovered systematically.The main conclusions of this paper are as follows:1.The type of auxiliary modifier was controlled in the hydrothermal reaction to prepare nanosheets and nanoparticle TiO2.On the basis of above experiment,the anatase TiO2 nanosheets with the thickness rank from 2.9 nm to 13.5 nm were prepared by controlling the amount of ethanol from 2 ml to 25 mL.The thinest nanosheets(2.9 nm)could achieve the highest photocatalytic hydrogen production performance(41.04 mmol· h-1 g-1),and the corresponding quantum efficiency(41.6%)was also the highest.2.The growth mechanism of(001)surface in anatase TiO2 nanosheets was revealed for the first time:Fluorine ions are bonded with Ti vacancies on the(001)surface,resulting in the reduction of the total energy of the system,thus making the nanosheets thinner.This mechanism can increase the efficiency of photoelectron-hole separation and improve the photocatalytic performance.However,this bond will be broken by alkaline lotion(such as NaOH,KOH and LiOH,etc.)washing method,and cations like Na+,K+ and Li+,etc.will replace the position of Ti vacancy,leading to the reduction of photogenerated electron-hole separation efficiency,and thereby reducing the photocatalytic performance.3.The above anatase TiO2 nanosheets were used as the substrate,and its homogeneous structure was obtained by simple annealing treatment.The effects of annealing temperature,holding time and the thickness of nanosheets on the growth of homojunction were studied systematically.We verified that when the annealing temperature is 450 ℃,holding time is 2 h,and the nanosheets are the thinest were the most helpful condition to generate homogeneous structure.The photocatalytic hydrogen production efficiency is 94.37 mmol ·h-1·g-1.The fully decomposed water efficiency is:H2 production efficiency is 3891.49 μgmol·h-1·g-1,O2 production efficiency is 516.43μmol·h-1·g-1,the ratio of H2 production and O2 production is 8:1.更多还原