磁控溅射制备Cu2O和Cu2O/TiO2复合膜及其光催化活性

引用本文

刘灿, 魏子栋, 张骞, 胡宝山, 齐学强, 陈四国, 丁炜. 磁控溅射制备Cu₂O和Cu₂O/TiO₂复合膜及其光催化活性 . 无机材料学报, 2012, 27(4): 395-399[LIU Can, WEI Zi-Dong, ZHANG Qian, HU Bao-Shan, QI Xue-Qiang, CHEN Si-Guo, DING Wei. Photocatalytic Activity of Cu₂O and Bilayer Cu₂O/TiO₂ Films Prepared by Magnetron Sputtering . Journal of Inorganic Materials, 2012, 27(4): 395-399] 复制到剪切板

Permissions

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

磁控溅射制备Cu₂O和Cu₂O/TiO₂复合膜及其光催化活性

刘灿, 魏子栋, 张骞, 胡宝山, 齐学强, 陈四国, 丁炜

重庆大学输配电装备及系统安全与新技术国家重点实验室, 化学化工学院, 重庆 400044

魏子栋, 教授. E-mail:zdwei@cqu.edu.cn

刘灿(1988-), 男, 硕士研究生. E-mail:liucan111@yahoo.com.cn

基金:国家自然科学基金(20806096); 国家重点实验室项目(2007DA10512711211); 中央高校基本科研业务费专项基金(CDJXS10221141和11132229);

中图分类号:O643 文献标志码:A 文章编号:1000-324X(2012)04-0395-05

Photocatalytic Activity of Cu₂O and Bilayer Cu₂O/TiO₂ Films Prepared by Magnetron Sputtering

LIU Can, WEI Zi-Dong, ZHANG Qian, HU Bao-Shan, QI Xue-Qiang, CHEN Si-Guo, DING Wei

State Key Laboratory of Power Transmission Equipment & System Security and New Technology, School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China

Fund:National Natural Science Foundation of China (20806096); The Program of State Key Laboratory (2007DA10512711211); Fundamental Research Funds for the Central Universities (NosCDJXS10221141 and 11132229);

Abstract

Cu₂O, TiO₂ and composite Cu₂O/TiO₂ films were deposited on slide glass by direct current (DC) reactive magnetron sputtering. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive spectrometry (EDS) were applied to characterize crystal structure, morphology and composition of the films, respectively. Photocatalytic activity was evaluated by the degradation of methylene blue (MB) with Xenon lamp. XRD results show that besides the initial (111) crystal plane at sputtering time of 5 min, (110) and (220) crystal planes gradually develop on the Cu₂O film with the increase of sputtering time. Our calculation result indicates that (111) crystal plane is more beneficial to absorption of O₂than other crystal planes. The photocatalytic activity of the Cu₂O/TiO₂ composite films first increases with increasing Cu₂O-deposited content, and then reaches the highest value when the deposited content of Cu₂O is 2.6mol%, and successively undergoes a drop. The enhancement of the photocatalytic activity is mainly attributed to alleviate the recombination of electron-hole pairs. Excessive Cu₂O will prolong the time for transferring of electrons to Cu₂O/TiO₂interface and holes to surface, which increases the recombination probability of electrons and holes, and thus reduces the quantum efficiency.

Keyword: magnetron sputtering; cuprous oxide; composite films; photocatalytic

Show Figures

半导体光催化技术可以将水中难于生物降解的有机物质彻底矿化, 具有除净度高、分解速率快和易操作等优点^{[ 1, 2, 3, 4]}. TiO₂以其催化活性高、氧化能力强、无毒、稳定性好而最为常用^{[ 5, 6, 7]}. 但是, 其禁带宽度较大, 太阳光的利用率较低, 光催化效率低^{[ 8, 9, 10]}. 减少光生空穴电子复合的一个有效方法是将TiO₂与某些窄带半导体进行复合^{[ 11, 12, 13]}. Cu₂O是一种能被可见光激发的p型半导体, 禁带宽度大约为 2.2 eV^{[ 14, 15, 16]}, 并且可与表面吸附的活性氧生成高活性的物质^{[ 17]}, 已有研究证明Cu₂O是良好的可见光催化剂^{[ 18]}. 但是, 单一的Cu₂O比较活泼, 且光生电子和空穴容易复合. 若将Cu₂O与TiO₂复合, 利用二者导带及价带位置的差别, 光生电子由Cu₂O的导带注入到TiO₂的导带上, 同时TiO₂的光生空穴也会向Cu₂O的价带迁移, 促进电子和空穴的分离, 提高光催化效率^{[ 11, 19, 20, 21]}. 为了克服悬浮催化剂难以回收的缺点, 本实验采用直流反应磁控溅射的方法, 制备了Cu₂O及不同Cu₂O含量的Cu₂O/TiO₂叠层复合薄膜, 通过对模拟污染物亚甲基蓝(MB)进行光催化降解, 研究了各种薄膜的光催化性能.

1 实验部分

1.1 Cu₂O、TiO₂和Cu₂O/TiO₂叠层复合薄膜的制备

实验采用JGP450型涡轮泵高分辨率离子溅射仪(中科院沈阳科仪研制中心有限公司).

溅射Cu₂O薄膜的制备条件为: 纯度为99.97%铜靶, 尺寸为60 mm×3 mm. 溅射气体和反应气体分别为高纯氩气(99.99%)和高纯氧气(99.99%). 实验衬底为普通玻璃(2.5 mm×3.8 mm), 使用前衬底依次在丙酮、乙醇和去离子水中超声清洗, 然后吹干备用. 溅射本底真空为1.0×10^-3Pa, 沉积过程中保持反应压强在1.0 Pa, 通入的氩、氧质量流量比为27:3, 溅射功率为100 W, 衬底温度为300℃, 薄膜沉积时间为5、15和30 min. 每次溅射前, 须在Ar气氛中预溅射2 min以除去靶表面的氧化物.

溅射TiO₂薄膜的制备条件为: 纯度为99.995%钛靶, 通入的氩氧质量流量比为10:2, Ti靶溅射功率为100 W, 衬底不加温, 将得到的薄膜放入管式炉中经过500℃煅烧退火3 h.

Cu₂O/TiO₂叠层复合薄膜制备条件为: 以退火后的TiO₂薄膜为衬底, 再按照之前溅射Cu₂O的条件沉积不同时间的Cu₂O, 得到不同Cu₂O厚度的Cu₂O/TiO₂叠层复合薄膜. 需要指出的是, 由于生成Cu₂O和TiO₂的氧气浓度不同, 很难通过溅射的方法获得Cu₂O/TiO₂混合结构的复合薄膜.

1.2 薄膜表征及模型计算分析

用X射线衍射仪(XRD, XRD-6000, Shimadzu)对沉积氧化物的晶体结构进行表征, X射线能谱仪(EDS, OXFORD Link-ISIS-300)对薄膜的元素组成进行分析. 场发射扫描电镜(FEI Nova 400, Peabody, MA, Netherlands)对薄膜的表面形貌进行了分析. 通过EDS表征不同厚度Cu₂O的复合薄膜中铜和钛元素含量的比值, 进而得到各种氧化物的组成含量.

采用Materials Studio软件中DMoL³程序来模拟Cu₂O(111)和Cu₂O(110)的几何构型和电子构型, 三层(2×2)的Cu₂O(111)和Cu₂O(110)表面的超晶胞的平板模型上. 全部计算工作使用DMol³程序包进行. 计算采用effective core potentials对原子内层电子冻结; 价电子采用双数值基组加极化函数展开(DNP); 交换相关势采用广义梯度近似和Perdew- Wang-91泛函(GGA-PW91)相结合的方法. 对各模型优化时, 将超晶胞平板模型的最底层固定, 采用1×1×1的Monkhorst-Pack K点计算氧分子在Cu₂O不同晶面的吸附能.定义O₂的吸附能为 E_abs(单位为kJ/mol), 其计算式为:

(1)

由于(220)晶面表面结构与(110)晶面相同, 因此只计算了(111)和(110)两个晶面作为对比.

1.3 光催化测试

光催化效果分析是利用模拟太阳光的氙灯(100 W, 北京畅拓)垂直照射薄膜分解溶液中的MB完成的. 通过紫外-可见分光光度仪(TU-1901, 北京普析通用仪器有限责任公司)测定640 nm的吸光度的变化, 计算得到光催化降解率( c₀- c)/ c₀.

2 结果与讨论

2.1 溅射Cu₂O薄膜的表征

图1是不同溅射时间获得的Cu₂O薄膜的XRD图谱, 从图中可以看出, 氧化物衍射峰出峰位置在29.55°、36.40°和61.34°, 分别对应Cu₂O的(110)、(111)和(220)晶面, 未出现CuO或者Cu相的衍射峰, 因此可以确定薄膜的成份为单一的Cu₂O. 从XRD图谱中还可以发现, 溅射时间为5 min时, 衍射谱中仅有Cu₂O(111)晶面衍射峰. 随着溅射时间的延长, Cu₂O (111)晶面衍射峰相对强度逐渐减弱, 而Cu₂O(110)和(220)衍射峰的强度迅速增强; 溅射30 min时, (110)和(220)晶面的衍射强度超过了(111)晶面. 可见溅射时间的增加促进了Cu₂O(110)和(220)晶面的生长.

	Figure Option View Download New Window
	图1 不同溅射时间获得的Cu₂O的XRD图谱Fig. 1 XRD patterns of Cu₂O after sputtened for different time

2.2 不同溅射时间Cu₂O光催化活性比较

图2是不同溅射时间获得的Cu₂O的光催化活性的比较, 从图中可以看出, 在实验的光强度照射下, 60 min内无催化剂时MB分子的光化学自敏化降解率为8.9%. 溅射时间为5、15和30 min得到的薄膜, 其MB降解率分别为29.4%、22.5%和12.4%.

	Figure Option View Download New Window
	图2 不同溅射时间获得的Cu₂O薄膜的光催化活性Fig. 2 Photocatalytic activity of Cu₂O film after deposited for different time

图3是Cu₂O不同晶面表面结构的模型图, 从图中可以看出, (111)晶面表面的Cu原子有更多的悬挂键. 根据孙宝珍等^{[ 22]}提出的氧分子在Cu₂O(111)晶面的吸附模型, 本工作计算了O₂在(110)和(111)晶面的吸附情况. O₂吸附后的结构模型和计算结果, 分别如图4和表1所示. 从计算结果可以看出, O₂在Cu₂O(110)晶面的吸附能为-44.78 kJ/mol, 属于物理吸附的范畴; 而在Cu₂O(111)晶面的吸附能为-157.45 kJ/mol, 属于化学吸附的范畴, 意味着O₂在Cu₂O(111)晶面的吸附强于在Cu₂O(110)晶面的吸附, 根据光催化机理, 这种强吸附作用有利于更多的氧分子捕获表面的光生电子, 提高电子-空穴的分离效率, 从而导致各薄膜活性不同的情况.

	Figure Option View Download New Window
	图3 Cu₂O(110)晶面(a)和(111)晶面(b)表面结构模型图Fig. 3 Structural models for Cu₂O (110) (a) and (111) (b) surfaceLight circles indicate Cu atoms, dark circles indicate O atoms

	Figure Option View Download New Window
	图4 Cu₂O(110)晶面(a)和(111)晶面(b)吸附O₂后的结构模型Fig. 4 Structural model for Cu₂O (110) (a) and (111) (b) surface after O₂ adsorptionLight circles indicate Cu atoms, dark circles indicate O atoms

表1 O₂在Cu₂O不同晶面的吸附参数 Table 1 Adsorption parameter of O₂ on different crystal planes of Cu₂O

2.3 TiO₂及Cu₂O/TiO₂复合薄膜的表征

图5为TiO₂薄膜和Cu₂O/TiO₂复合薄膜的XRD图谱, 从图中可以看出, 经过500℃退火后的TiO₂谱图中出现三个明显XRD衍射峰, 分别位于25.28°、37.85°和54.11°, 对比标准衍射峰卡片(PDF: 21-1272), 可以确定它们分别为TiO₂锐钛矿(101)、(004)和(105)晶面的衍射峰. 根据Scherrer公式计算薄膜晶粒的平均大小为21.8 nm. 表面的Cu₂O以(111)晶面存在, 根据Scherrer公式计算其晶粒的平均大小为12.5 nm. 从上面的计算可以得出, Cu₂O (111)晶面的存在有利于复合薄膜对氧分子的吸附. 图6为TiO₂和Cu₂O/TiO₂复合薄膜的SEM照片, 从图中可以看出, 复合薄膜Cu₂O/TiO₂表面的颗粒粒径小于TiO₂薄膜, 这种结构特征有利于比表面积的增大和对亚甲基蓝分子和氧分子的吸附.

	Figure Option View Download New Window
	图5 TiO₂和Cu₂O/TiO₂复合薄膜的XRD图谱Fig. 5 XRD patterns of TiO₂ and Cu₂O/TiO₂ composite film Sputtering Cu₂O for 6 s

	Figure Option View Download New Window
	图6 TiO₂(a)和Cu₂O/TiO₂(b)复合薄膜的SEM照片Fig. 6 SEM images of TiO₂ (a) and Cu₂O/TiO₂ composite films (b)Sputtering Cu₂O for 6 s

2.4 TiO₂及Cu₂O/TiO₂复合薄膜的光催化活性

图7为Cu₂O/TiO₂复合薄膜中Cu₂O含量对MB降解率的影响(降解时间为60 min), 从图中可以看出, 纯TiO₂薄膜对MB的降解率为57.8%, 复合薄膜对MB的光催化降解率随着Cu₂O含量的增加先升高后降低. 在Cu₂O含量为2.6 mol% (Cu₂O的溅射时间为6 s)时催化活性最好, MB降解率达到了73.6%. 这是由于Cu₂O导带更负, 而氧化钛导带更正^{[ 11, 20]}, 光生电子从Cu₂O的导带转移到TiO₂的导带, 造成电子在TiO₂晶体导带中积累; 而TiO₂的价带空穴则会向表面Cu₂O的价带迁移, 从而使电子-空穴对有效分离, 增强了复合薄膜的光催化效率^{[ 21]}. Cu₂O薄膜过厚时, 表面的Cu₂O层内产生的光生电子离Cu₂O/TiO₂界面较远, 光生电子到达界面需要更长的时间, 光生电子不能发生有效的迁移. 此外, 薄膜表面光生电子迁移到界面所需要的时间越长, 电子和空穴复合的几率越大, 因此复合薄膜的光催化效率降低. 从图7中还可以看出, 当表面Cu₂O含量大于6.5mol%(溅射时间大于15 s)时, 表面Cu₂O薄膜太厚, 复合薄膜的催化效果和单一Cu₂O薄膜的催化效果相近.

	Figure Option View Download New Window
	图7 Cu₂O/TiO₂复合薄膜中Cu₂O含量对亚甲基蓝(MB)降解率的影响Fig. 7 Dependence of MB degradation rate on Cu₂O content in Cu₂O/TiO₂ composite_film

3 结论

通过直流反应磁控溅射制备了Cu₂O薄膜及不同厚度的Cu₂O/TiO₂复合薄膜, 通过XRD分析发现当反应溅射时间为5 min时, Cu₂O薄膜由单一的(111)晶面组成; 反应时间的延长促进了Cu₂O(110)和(220)晶面的生长. 光催化活性测试和理论计算结果表明, (111)晶面的光催化效率和对氧气分子的吸附优于(110)及(220)晶面. Cu₂O/TiO₂复合薄膜光催化降解MB的实验表明, Cu₂O含量为2.6mol%的复合薄膜对MB的光催化降解率最好, 60 min内达到了73.6%. 过量的Cu₂O会导致表面的Cu₂O层内产生的光生电子离Cu₂O/TiO₂界面较远, 增加光生电子迁移到界面所需要的时间, 提高电子和空穴复合的几率. 当Cu₂O含量大于6.5mol%时, 复合薄膜Cu₂O/TiO₂与单一Cu₂O薄膜的活性接近.

Reference

View Option

[1]	Zhu X L, Yuan C W, Bao Y C, et al. Photocatalytic degradation of pesticide pyridaben on TiO₂ particles. J. Mol. Catal. , 2005, 229(1/2): 95-105. [Cited within: 1] [JCR: 3.187]
[2]	ZHANG Qing-Hong, GAO Lian, GUO Jing-Kun. Photocatalytic activity of nanosized TiO₂. Journal of Inorganic Materials, 2000, 15(3): 556-560. [Cited within: 1] [JCR: 0.531] [CJCR: 1.106]
[3]	翟晓辉, 龙绘锦, 董江舟, 等(ZHAI Xiao-Hui, et al). N-TiO₂/ZnO复合纳米管阵列的掺杂机理及其光催化活性. 物理化学学报(Acta Physico - Chimica Sinica), 2010, 26(3): 663-668. [Cited within: 1] [JCR: 0.869] [CJCR: 1.044]
[4]	Nguyen-Phan T D, Pham V H, Cuong T V, et al. Fabrication of TiO₂ nanostructured ﬁlms by spray deposition with high photocatalytic activity of methylene blue. Mater. Lett. , 2010, 64(12): 1387-1390. [Cited within: 1] [JCR: 2.224]
[5]	朱建, 杨俊, 陈麟, 等(ZHU Jian, et al). 低温苯甲醇醇解法制备高活性锐钛矿型纳米晶TiO₂光催化剂. 催化学报(Chinese Journal of Catalysis), 2006, 27: 171-177. [Cited within: 1]
[6]	Dillert R, Cassano A E, Goslich R, et al. Large scale studies in solar catalytic wastewater treatment. Catal. Today, 1999, 54(2/3): 267-282. [Cited within: 1] [JCR: 2.98]
[7]	Cao S, Yeung K L, Yue P L. Preparation of freestand ing and crack-free titania–silica aerogels and their performance for gas phase, photocatalytic oxidation of VOCs. Appl. Catal. B, 2006, 68(3/4): 99-108. [Cited within: 1] [JCR: 5.825]
[8]	Zhao G L, Tian Q H, Li Q H, et al. Effects of HPC on the microstructure and hydrophilicity of Sol-Gel-derived TiO₂ films. Surf. Coat. Tech. , 2005, 198(1/2/3): 55-58. [Cited within: 1]
[9]	Zhang W J, He Y Q, Qi Q. Synthesize of porous TiO₂ thin ﬁlm of photocatalyst by charged microemulsion templating. Mater. Chem. Phys. , 2005, 93(2/3): 508-515. [Cited within: 1] [JCR: 2.072]
[10]	籍宏伟, 马万红, 黄应平, 等. 可见光诱导TiO₂光催化的研究进展. 科学通报, 2003, 48(21): 2199-2204. [Cited within: 1]
[11]	Bessekhouad Y, Robert D, Weber J V. Photocatalytic activity of Cu₂O/TiO₂, Bi₂O₃/TiO₂ and ZnMn₂O₄/TiO₂ heterojunctions. Catal. Today, 2005, 101(3/4): 315-321. [Cited within: 3] [JCR: 2.98]
[12]	Serpone N, Maruthamuthu P, Pichat P, et al. Exploiting the interparticle electron transfer process in the photocatalysed oxidation of phenol, 2-chlorophenol and pentachlorophenol: chemical evidence for electron and hole transfer between coupled semiconductors J. Photoch. Photobio. A, 1995, 85(3): 247-245. [Cited within: 1] [JCR: 2.416]
[13]	Kang M G, Hen H E, Kim K J. Enhanced photodecomposition of 4-chlorophenol in aqueous solution by deposition of CdS on TiO₂. J. Photoch. Photobio. A, 1999, 125(1/2/3): 119-125. [Cited within: 1] [JCR: 2.416]
[14]	Nolan M, Elliott S D. The p-type conduction mechanism in Cu₂O: a first principles study. Phys. Chem. Chem. Phys. , 2006, 8: 5350-5358. [Cited within: 1] [JCR: 3.829]
[15]	CHEN Zhi-Gang, TANG Yi-Wen, JIA Zhi-Jie, et al. Electrodeposition and characterization of Cu₂O thin films on transparent conducting glass. Journal of Inorganic Materials, 2005, 20(2): 367-372. [Cited within: 1] [JCR: 0.531] [CJCR: 1.106]
[16]	Ghijsen J, Tjeng L H, Eskes H, et al. Resonant photoemission study of the electronic structure of CuO and Cu₂O. Phys. Rev. B, 1990, 42(4): 2268-2274. [Cited within: 1]
[17]	甄开吉, 王国甲, 李荣生, 等. 催化作用基础, 3版. 北京: 科学出版社, 2005: 226-227. [Cited within: 1]
[18]	Hava M, Kondo T, Komoda M, et al. Cu₂O as a photocatalyst for overall water splitting under visible light irradiation. Chem. Commun. , 1998, 3: 357-358. [Cited within: 1] [JCR: 6.378]
[19]	Xu Y H, Liang D H, Liu M L, et al. Preparation and characterization of Cu₂O-TiO₂: efﬁcient photocatalytic degradation of methylene blue. Mater. Res. Bull. , 2008, 43(12): 3474-3482. [Cited within: 1] [JCR: 1.913]
[20]	Siripala W, Ivanovskaya A, Jaramillo T F, et al. A Cu₂O-TiO₂ heterojunction thin ﬁlm cathode for photoelectrocatalysis. Sol. Energ. Mat. Sol. C, 2003, 77(3): 229-237. [Cited within: 2] [JCR: 4.63]
[21]	Yasomanee J P, Band ara J. Multi-electron storage of photoenergy using Cu₂O-TiO₂ thin ﬁlm photocatalyst. Sol. Energ. Mat. Sol. C, 2008, 92(3): 348-352. [Cited within: 2] [JCR: 4.63]
[22]	孙宝珍, 陈文凯, 王霞, 等(SUN Bao-Zhen, et al). 氧分子在Cu₂O(111)表面吸附与解离的理论研究. 无机化学学报(Chinese Journal of Inorganic Chemistry), 2008, 24(3): 340-350. [Cited within: 1] [JCR: 0.72] [CJCR: 0.914]

2005

3.187

0.0

... 半导体光催化技术可以将水中难于生物降解的有机物质彻底矿化, 具有除净度高、分解速率快和易操作等优点^[1,2,3,4] ...

2000

0.531

1.106

ZHANG

Qing-Hong

, GAO

Lian

, GUO

Jing-Kun

. Photocatalytic activity of nanosized TiO₂. Journal of Inorganic Materials, 2000, 15(3): 556-560.

In the present study, particulate suspensions of nanosized(particle size less than 10nm) anatase and rutile TiO₂ under UV irradiation in a loop
photoreactor catalyzed the oxidation of a typical organic contaminant: phenol. Both nanosized anatase and rutile TiO₂ have a much higher photocatalytic
activity than bulk TiO₂ (particle size more than 100nm), however, anatase shows a higher selectivity for complete mineralization: the concentration of
p-quinone as intermediate of this photocatalytic reaction is at lower level than those of rutile. Species adsorbed by titanium dioxide such as H₂O and OH
play a significant role in the photodegradation of phenol as well as particle size . With the decrement of particle size especially less than 15nm,
the photocatalytic activity of TiO₂ increases dynamically.

State Key Laboratory of High Performance Ceramics and Superfine Microstructure; Shanghai Instituteof Ceramics; Shanghai 200050; China

以苯酚的光催化降解为模型反应，研究了锐钛矿相和金红石相二氧化钛纳米晶（7～40nm）的光催化活性．与市售的氧化钛相比，两种晶相的纳米氧化钛均有很高的光催化活性，锐钛矿相氧化钛对苯酚的深度矿化有更高的选择性．TiO₂吸附的水及羟基会降低氧化钛的光催化活性．由于粒径减小使氧化钛的吸收带边界蓝移，粒径小的氧化钛有更高的催化活性，粒径＜15nm时，显示出量子尺寸效应．

... 半导体光催化技术可以将水中难于生物降解的有机物质彻底矿化, 具有除净度高、分解速率快和易操作等优点^[1,2,3,4] ...

2010

0.869

1.044

翟晓辉, 龙绘锦, 董江舟, 等(ZHAI

Xiao-Hui

, et al). N-TiO₂/ZnO复合纳米管阵列的掺杂机理及其光催化活性. 物理化学学报(Acta Physico - Chimica Sinica), 2010, 26(3): 663-668.

TiO2/ZnO and N-doped TiO2/ZnO composite nanotube arrays were synthesized by the sol-gel method using ZnOnanorod arrays as a template. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance UV-Vis spectroscopy (UV-Vis) were used to characterize the samples. The nanotubes had a uniform hexagonal shape. The diameter and wall thickness of the nanotubes were about 100 nm and 20 nm, respectively. Some N dopants were substitutionally doped into the TiO2 lattice, while the N-Ox, N-C, and N-N were chemically absorbed onto the surface of the TiO2/ZnO composite nanotubes. Dopant-induced narrowing of the bandgap resulted from the doping of N ions into the TiO2 lattices. The surface N species enhanced the visible-light response and promoted the separation of photogenerated carriers. Compared with the TiO2/ZnO composite nanotube arrays, the N-TiO2/ZnO composite nanotube arrays exhibited higher photocatalytic activity.

College of Physics, Nankai University, Tianjin 300071, P. R. China; Teda Applied Physics School, Nankai University, Tianjin 300457, P. R. China

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.

... 半导体光催化技术可以将水中难于生物降解的有机物质彻底矿化, 具有除净度高、分解速率快和易操作等优点^[1,2,3,4] ...

2010

2.224

0.0

... 半导体光催化技术可以将水中难于生物降解的有机物质彻底矿化, 具有除净度高、分解速率快和易操作等优点^[1,2,3,4] ...

2006

0.0

... TiO₂以其催化活性高、氧化能力强、无毒、稳定性好而最为常用^[5,6,7] ...

1999

2.98

0.0

... TiO₂以其催化活性高、氧化能力强、无毒、稳定性好而最为常用^[5,6,7] ...

2006

5.825

0.0

... TiO₂以其催化活性高、氧化能力强、无毒、稳定性好而最为常用^[5,6,7] ...

2005

0.0

... 但是, 其禁带宽度较大, 太阳光的利用率较低, 光催化效率低^[8,9,10] ...

2005

2.072

0.0

... 但是, 其禁带宽度较大, 太阳光的利用率较低, 光催化效率低^[8,9,10] ...

2003

0.0

... 但是, 其禁带宽度较大, 太阳光的利用率较低, 光催化效率低^[8,9,10] ...

2005

2.98

0.0

... 减少光生空穴电子复合的一个有效方法是将TiO₂与某些窄带半导体进行复合^[11,12,13] ...

... 若将Cu₂O与TiO₂复合, 利用二者导带及价带位置的差别, 光生电子由Cu₂O的导带注入到TiO₂的导带上, 同时TiO₂的光生空穴也会向Cu₂O的价带迁移, 促进电子和空穴的分离, 提高光催化效率^{[11, 19,20,21]} ...

... 这是由于Cu₂O导带更负, 而氧化钛导带更正^{[11, 20]}, 光生电子从Cu₂O的导带转移到TiO₂的导带, 造成电子在TiO₂晶体导带中积累 ...

1995

2.416

0.0

... 减少光生空穴电子复合的一个有效方法是将TiO₂与某些窄带半导体进行复合^[11,12,13] ...

1999

2.416

0.0

... 减少光生空穴电子复合的一个有效方法是将TiO₂与某些窄带半导体进行复合^[11,12,13] ...

2006

3.829

0.0

Nolan

, Elliott

S D

. The p-type conduction mechanism in Cu₂O: a first principles study. Phys. Chem. Chem. Phys. , 2006, 8: 5350-5358.

Tyndall National Institute, Lee Maltings, Prospect Row, Cork, Ireland. michael.nolan@tyndall.ie

Materials based on Cu2O are potential p-type transparent semiconducting oxides. Developing an understanding of the mechanism leading to p-type behaviour is important. An accepted origin is the formation of Cu vacancies. However, the way in which this mechanism leads to p-type properties needs to be investigated. This paper presents a first principles analysis of the origin of p-type semiconducting behaviour in Cu2O with 1.5 and 3% Cu vacancy concentrations. Plane wave density functional theory (DFT) with the Perdew-Burke Ernzerhof (PBE) exchange-correlation functional is applied. In order to investigate the applicability of DFT, we firstly show that CuO, with 50% Cu vacancies cannot be described with DFT and in order to obtain a consistent description of CuO, the DFT + U approach is applied. The resulting electronic structure is consistent with experiment, with a spin moment of 0.64 mu(B) and an indirect band gap of 1.48 eV for U = 7 eV. However, for a 3% Cu vacancy concentration in Cu2O, the DFT and DFT + U descriptions of Cu vacancies are similar, indicating that DFT is suitable for a small concentration of Cu vacancies; the formation energy of a Cu vacancy is no larger than 1.7 eV. Formation of Cu vacancies produces delocalised hole states with hole effective masses consistent with the semiconducting nature of Cu2O. These results demonstrate that the p-type semiconducting properties observed for Cu2O are explained by a small concentration of Cu vacancies.

PMID: 19810413

... 2 eV^[14,15,16], 并且可与表面吸附的活性氧生成高活性的物质^[17], 已有研究证明Cu₂O是良好的可见光催化剂^[18] ...

2005

0.531

1.106

CHEN

Zhi-Gang

, TANG

Yi-Wen

, JIA

Zhi-Jie

, et al. Electrodeposition and characterization of Cu₂O thin films on transparent conducting glass. Journal of Inorganic Materials, 2005, 20(2): 367-372.

Electrochemical behavior of cuprous oxide was investigated by using the catholic reduction electrochemical method. The effects of some technological factors on Cu₂O thin films electrodeposited
on transparent conducting glass were also studied. Cu₂O thin films were characterized by Talystep, X-ray diffraction (XRD) , scanning electron microscope (SEM) and X-ray photoelectron spectroscope
(XPS). The optimum technological conditions were obtained as follows: the applied potential was -0.22～-0.45V (vs SCE) , bath temperature was 60℃, bath pH was 5.5～6.0 and concentration of (CH₃COO)₂Cu
was in the range 0.015～0.040mol/L. The results showed that with the increase of bath temperature, the grain size of Cu₂O film increased from 0.2μm to 0.4μm and it started to have (111) preferred
orientation at 60℃. The film had high purity and was porous.

College of Physical Science and Technology; Central China Normal University; Wuhan 430079; China

研究了用简单铜盐通过阴极还原氧化亚铜的电化学行为,讨论了一些工艺因素对在导电玻片上电沉积Cu₂O薄膜的影响,并对所制备的Cu₂O薄膜分别用台阶仪、X射线衍射仪(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)进行表征.得到的较佳工艺条件为:电势-0.22--0.45V(vs SCE),温度为60℃,pH值为5.5-6.0,(CH₃COO)₂Cu浓度为 0.015-0.04mol／L.表征结果发现,随池温的升高,晶粒尺寸从0.2μm增加到0.4μm,60℃沉积的Cu₂O薄膜开始具有(111)面择优取向,Cu2O膜纯度高,薄膜表面呈网络多孔结构.

... 2 eV^[14,15,16], 并且可与表面吸附的活性氧生成高活性的物质^[17], 已有研究证明Cu₂O是良好的可见光催化剂^[18] ...

1990

0.0

Ghijsen

, Tjeng

L H

, Eskes

, et al. Resonant photoemission study of the electronic structure of CuO and Cu₂O. Phys. Rev. B, 1990, 42(4): 2268-2274.

PMID: 9995674

... 2 eV^[14,15,16], 并且可与表面吸附的活性氧生成高活性的物质^[17], 已有研究证明Cu₂O是良好的可见光催化剂^[18] ...

2005

0.0

... 2 eV^[14,15,16], 并且可与表面吸附的活性氧生成高活性的物质^[17], 已有研究证明Cu₂O是良好的可见光催化剂^[18] ...

1998

6.378

0.0

... 2 eV^[14,15,16], 并且可与表面吸附的活性氧生成高活性的物质^[17], 已有研究证明Cu₂O是良好的可见光催化剂^[18] ...

2008

1.913

0.0

2003

4.63

0.0

... 这是由于Cu₂O导带更负, 而氧化钛导带更正^{[11, 20]}, 光生电子从Cu₂O的导带转移到TiO₂的导带, 造成电子在TiO₂晶体导带中积累 ...

2008

4.63

0.0

... 而TiO₂的价带空穴则会向表面Cu₂O的价带迁移, 从而使电子-空穴对有效分离, 增强了复合薄膜的光催化效率^[21] ...

2008

0.72

0.914

孙宝珍, 陈文凯, 王霞, 等(SUN

Bao-Zhen

, et al). 氧分子在Cu₂O(111)表面吸附与解离的理论研究. 无机化学学报(Chinese Journal of Inorganic Chemistry), 2008, 24(3): 340-350.

Interaction of atomic and molecular oxygen with perfect and defective Cu₂0 (111) surfaces has been studied by periodic density functional theory coupled with slab models. Different kinds of possible modes of O and O₂ adsorbed on Cu₂O (111) surface and possible dissociation pathways were calculated. Meanwhile, different electronic states, i.e., the singlet and the triplet states were considered in the computation. The optimization of the geometry, calculation of the adsorption energy, vibrational frequency and analysis of the Mulliken population were carried out. The results indicate that Cu_CSA site is slightly more favorable than Cu_CUS for O adsorption, and for O₂ adsorption over perfect surface, Cu_CUS site is the most advantageous position, especially for O₂ with end-on type. For O₂ adsorption over the deficient surface, it has a larger adsorption energy compared to O₂ adsorption over the perfect surface and the O-O bond strength is considerably weakened when 05 lies flatly on the oxygen vacancy site and lies flatly over 1-vacancy bridge site. And the oxygen adspecies is characteristic of a classical O₂^- ion on perfect surface, whereas is O₂^2- ion on oxygen-deficient surface. The calculations for transition states show that the dissociation reaction of O₂ on deficient surface is highly exothermic with a very small barrier height.

本文采用密度泛函方法结合周期性平板模型,研究了氧原子和氧分子在完整和存在缺陷的Cu₂O(111)表面的吸附。计算结果表明氧原子倾向于吸附在配位饱和的Cu_CSA位,而对于氧分子,则强烈倾向于吸附在配位不饱和的Cu_CUS位。氧分子在含有氧空位的缺陷表面的优势吸附位为平行吸附于空位上方的桥位。过渡态的计算表明氧分子在缺陷表面的解离是一个活化能很小的放热过程。

... 根据孙宝珍等^[22]提出的氧分子在Cu₂O(111)晶面的吸附模型, 本工作计算了O₂在(110)和(111)晶面的吸附情况 ...