宽光谱响应碳量子点复合材料的制备及其光催化性能研究

PREPARATION AND PHOTOCATALYTIC

ACTIVITY OF COMPOSITES WITH WIDE

SPECTRAL RESPONSE

ABSTRACT

Semiconductor photocatalytic technology is one of the important ways for human to deal with energy shortage and environmental pollution.However, most of the traditional semiconductor photocatalytic materials only absorb the UV light and a part of the visible light of the solar spectrum,which utilization of sunlight is very limited.Therefore,it is significant to study new semiconductor photocatalysts with wide spectral response.Carbon quantum dots(CQDs)is a new type of zero-dimensional carbon nanomaterials with a quasi-spherical structure and good optical stability.Significantly,the excellent upconversion luminescence properties of CQDs,which can convert the longer wavelength light into shorter wavelength light.The up-converted PL of CQDs infer the possibility to construct CQDs based complex photocatalytic systems to harness the full spectrum of sunlight.Therefore,we constructed composites with CQDs and photocatalysts which have wide spectral response.The main research contents are as follows:

(1)The CQDs/TiO2composites photocatalysts were prepared by an ultrasonic method.The compositions,structures and optical properties of CQDs/TiO2composites were detected through XRD,FT-IR,HRTEM and DRS. The results indicated CQDs can successfully attach to the surface of TiO2and result in a red shift of the absorption edge of catalyst.The photocatalytic activity of the obtained materials with different concentration of CQDs were evaluated by degradation of rhodamine B(RhB)under simulated sunlight and monochromatic light irradiation.The results showed the CQDs/TiO2composites exhibit excellent ability of photocatalytic activity under simulated sunlight and the activity get to the best when the concentration of CQDs was1.5mg/mL. Moreover,it was found the available range of spectrum of CQDs/TiO2 composites are significantly broadened,and the CQDs/TiO2even showed effective photocatalytic performance under850nm light irradiation.The resulted of PL and transient photocurrent responses indicated the wide spectral response of CQDs/TiO2composites can be ascribed to the unique up-converted photoluminescence behavior of CQDs.

(2)The I-BiOBr/CQDs composites were successfully fabricated by a facile one-step alcohol soluble hydrolysis method with Bi(NO3)3·5H2O as the bismuth source and ethylene glycol source.The compositions,structures and morphology properties of I-BiOBr/CQDs composites were detected through XRD,FT-IR, XPS,SEM and HRTEM.The results indicated the iodide modification is surface decoration and CQDs can successfully attach to the surface of I-BiOBr.

I-BiOBr/CQDs samples mainly exhibited similar flower-like microspherical structure composed of nanosheets.The photocatalytic activity of the obtained materials were evaluated by degradation of methyl orange(MO).The I-BiOBr/CQDs composites showed excellent visible light photocatalytic activity and the available range of spectrum is significantly broadened,the I-BiOBr/CQDs even showed effecive photocatalytic performance under850nm light irradiation.The unique photoluminescence(PL)upconversion property of CQDs were detected through PL,CQDs could be excited by long-wavelength light(500~1000nm)and the upconverted emission is located in the range of 350~550nm.DRS and Mott-Schottky demonstrated that the I?ion decoration can higher the VB level of BiOBr to modulate the band structure,which could better utilize the upconversion property of CQDs.After studied the photocatalytic mechanism of I-BiOBr/CQDs composites,founding that the excellent photocatalytic activity of as-prepared samples could be ascribed to the couple effects of I?ion decoration and the unique up-converted photoluminescence behavior of CQDs.

KEY WORDS:CQDs,TiO2,BiOBr,photocatalytic,wide spectral response

摘要.........................................................................................................................................I ABSTRACT..............................................................................................................................III 第一章绪论. (1)

1.1引言 (1)

1.2光催化技术 (1)

1.2.1光催化原理 (1)

1.2.2半导体光催化材料 (2)

1.2.3现阶段光催化技术所面临的问题 (3)

1.2.4光催化剂的改性 (4)

1.3上转换材料 (6)

1.4碳量子点 (6)

1.4.1碳量子点简介 (6)

1.4.2碳量子点的性质 (7)

1.4.3具有上转换荧光碳量子点的合成方法 (9)

1.5碳量子点复合材料在光催化领域的研究现状 (10)

1.6选题意义及研究内容 (14)

1.6.1选题意义 (14)

1.6.2研究内容 (15)

第二章实验部分 (17)

2.1试剂与仪器 (17)

2.2复合光催化材料的制备 (18)

2.2.1CQDs/TiO2复合光催化材料的制备 (18)

2.2.2CQDs/I-BiOBr复合光催化材料的制备 (19)

2.3催化剂的表征方法 (19)

2.4光催化活性评价 (20)

第三章宽光谱响应CQDs/TiO2复合材料的制备及其光催化活性 (21)

3.1引言 (21)

太原理工大学硕士研究生学位论文

3.2实验部分 (21)

3.2.1CQDs/TiO2复合光催化剂的制备 (21)

3.2.2CQDs/TiO2复合光催化剂的表征 (22)

3.2.3光催化活性评价 (22)

3.3结果与讨论 (23)

3.3.1XRD分析 (23)

3.3.2FT-IR分析 (24)

3.3.3形貌分析 (24)

3.3.4催化剂活性与稳定性分析 (26)

3.3.5PL分析 (29)

3.3.6UV-vis DRS分析 (29)

3.3.7光电化学性质 (30)

3.3.8捕获剂实验 (31)

3.3.9光催化反应机理 (32)

3.4本章小结 (33)

第四章宽光谱响应CQDs/I-BiOBr复合材料的制备及其光催化性能研究 (35)

4.1引言 (35)

4.2实验部分 (35)

4.2.1CQDs/I-BiOBr复合光催化材料的制备 (35)

4.2.2CQDs/I-BiOBr复合光催化剂的表征 (36)

4.2.3光催化活性评价 (37)

4.3结果与讨论 (37)

4.3.1XRD分析 (37)

4.3.2FT-IR分析 (38)

4.3.3XPS分析 (39)

4.3.4形貌分析 (41)

4.3.5催化剂活性与稳定性分析 (44)

4.3.6PL分析 (47)

4.3.7能带结构分析 (48)

VIII

太原理工大学硕士研究生学位论文

4.3.8光电化学性质 (50)

4.3.9捕获剂实验及ESR分析 (51)

4.3.10光催化反应机理 (52)

4.4本章小结 (53)

第五章结论与展望 (55)

5.1结论 (55)

5.2展望 (56)

参考文献 (57)

致谢 (67)

攻读硕士学位期间发表的论文 (69)

太原理工大学硕士研究生学位论文