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摘要:采用电化学沉积方法,选择聚乙二醇(PEG400)和乙二胺(EDA)为添加剂,直接在ITO导电玻璃上制备了有序阵列的ZnO纳米棒,以及ZnO纳米棒上生长纳米棒微纳分级结构。采用化学浴沉积法均匀沉积Sb2S3纳米粒子,制备了Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构。利用扫描电子显微镜(SEM)、X射线衍射(XRD)、紫外可见吸收光谱(UVvis)、瞬态光电流等分析手段对其形貌、结构和光电化学性能进行了表征和测试。研究表明,Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构阵列膜的光电流明显高于Sb2S3/ZnO纳米棒壳核结构阵列。
关键词:光电化学;Sb2S3纳米粒子;ZnO纳米棒;微纳分级结构;壳核结构
中图分类号:O649文献标志码:A
Photoelectrochemical properties of hierarchical ZnO micronanostructure sensitized with Sb2S3 nanoparticles[J].Journal of Hebei University of Science and Technology,2016,37(1):2632.Photoelectrochemical properties of hierarchical ZnO micro
nanostructure sensitized with Sb2S3 nanoparticles
GUO Zhimin1, HAO Yanzhong1,2, PEI Juan2, SUN Bao2, LI Yingpin2
(1.School of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, China; 2.School of Science, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, China)
Abstract:By using electrochemical deposition method, and assisted with additions of PEG400 and EDA, wellaligned ZnO nanorods and hierarchical ZnO micronanostructure are fabricated directly on indium doped tin oxide coated conducting glass (ITO) substrate. The shellcore Sb2S3/ZnO nanorod structure and the shellcore hierarchical Sb2S3/ZnO micronanostructure are prepared by chemical bath deposition method. SEM, XRD, UVVis and photocurrent test are used to characterize the morphology, nanostructures and their photoelectrochemical properties. The studies show that the photocurrent on the array membranes with shellcore hierarchical Sb2S3/ZnO micronanostructure is apparently higher than that with shellcore Sb2S3/ZnO nanorods array.
Keywords: photoelectrochemistry; Sb2S3 nanoparticles; ZnO nanorods; micronano hierarchical structure; shellcore nanostructure
一维ZnO纳米半导体材料提供了直接有序的电荷传输通道,提高了光生电荷的分离效率,在太阳电池电极材料方面得到了广泛应用[18]。近年来,人们通过电化学沉积法[911]、水热/溶剂热法等[1213]相继合成了ZnO纳米棒,ZnO纳米棒的微纳分级结构[1416]因高的比表面积和多电子传输通道等优点吸引了很多研究者的关注。XU等[17]利用两步电化学沉积方法制备了ZnO纳米棒分级结构,产品展现出优良的光电性能。王玉辉[18]通过低温溶液法制备的毛笔状ZnO纳米棒分级结构具有很好的紫外发光性能、较高的结晶质量及较低的缺陷密度。ZnO微纳分级结构在太阳电池方面也已经得到了应用。例如:SHI等[19]基于ZnO分级结构制备的染料敏化太阳电池光电转换效率达到了6.42%;ZHENG等[20]利用化学浴沉积法制备的ZnO纳米棒分级结构组成的杂化太阳电池的效率相对于单纯的ZnO纳米棒提高了32.7%。Sb2S3作为一种直接带隙的半导体材料,其能带间隙为1.7~1.8 eV[2122],适合作为敏化剂用于太阳电池的电极材料。Sb2S3量子点作为敏化剂及光吸收材料在制备固态染料敏化太阳电池[2324]、无机薄膜太阳电池[25]及杂化太阳电池[2627]方面得到了重要应用。
河北科技大学学报2016年第1期郭志敏,等:Sb2S3纳米粒子敏化ZnO微纳分级结构的光电化学性能本文在电化学方法制备ZnO纳米棒和ZnO纳米棒上生长纳米棒微纳分级结构的基础上,采用化学浴沉积法沉积Sb2S3 纳米粒子,制备了Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构,并对其光电化学性能进行了表征测试。 1实验过程
1.1电化学法制备ZnO纳米棒阵列膜
电化学沉积采用三电极体系的电解池,工作电极为洁净的ITO导电玻璃,对电极为Pt电极,参比电极为饱和甘汞电极,在油浴恒温70 ℃的条件下采用恒电位模式电沉积1.5 h。具体过程如下:在0.012 5 mol/L,15 mL的Zn(NO3)2水溶液中加入30 μL聚乙二醇,于-1.1 V恒定电势下电沉积3~5 min制备种子层,然后向沉积液中加入8~20 μL的EDA,继续沉积1.5 h,制备高度取向的ZnO纳米棒阵列。将得到的产物用去离子水和无水乙醇交替冲洗,自然干燥,之后于马弗炉中400 ℃温度下煅烧1 h,即可得到结晶良好的ZnO纳米棒阵列膜。
1.2 ZnO纳米棒上生长纳米棒微纳分级结构阵列膜的制备
以沉积有ZnO纳米棒阵列的ITO导电玻璃为工作电极,二次电沉积得到ZnO纳米棒上生长纳米棒微纳分级结构。电解液配制如下:在磁力搅拌器不断搅拌下,向15 mL、浓度为0.025 mol/L的Zn(NO3)2水溶液中以微量注射器加入氨水,溶液开始变浑浊,继续缓慢加入氨水,直至溶液逐渐变为澄清,二次电沉积的电解液每次沉积前新鲜配制。沉积电势为-1.03 V,沉积时间为0.5 h。将沉积所得的产物用去离子水和无水乙醇交替冲洗,并于烘箱中干燥。热处理过程中将沉积有样品的ITO导电玻璃在N2气氛中于400 ℃退火1 h,再自然冷却至室温。
1.3壳核式Sb2S3/ZnO纳米棒、壳核式Sb2S3/ZnO纳米棒上生长纳米棒分级结构的制备
采用化学浴沉积法制备Sb2S3/ZnO壳核式纳米结构。沉积液配制如下:将0.65 g的SbCl3加入2.5 mL丙酮中溶解,加入1 mol/L 的Na2S2O3水溶液25 mL,搅拌均匀,最后加入二次水,使溶液总体积为100 mL。将沉积有ZnO纳米棒和ZnO纳米棒上生长纳米棒分级结构的ITO导电玻璃基底垂直浸入上述溶液中,于10 ℃下反应1 h。沉积结束后,将沉积有样品的ITO导电玻璃用二次去离子水冲洗数次,并在烘箱中干燥1 h。最后,在N2保护的管式炉中于320 ℃煅烧1 h,即可得到壳核式Sb2S3/ZnO纳米棒阵列和壳核式Sb2S3/ZnO纳米棒上生长纳米棒的分级结构阵列。
1.4表征及光电性能测试
采用日本HITACHI公司的S4800I型发射场扫描电镜(SEM)观察阵列膜的形貌和尺寸,采用日本Rigaku公司的D/MAX2500 X射线衍射仪检测阵列膜的晶型和结构,采用日本日立公司的U3900型紫外可见吸收光谱仪对样品的光吸收范围进行测定。
光电化学测试在三电极体系中进行,支持电解质为0.1 mol/L的KSCN溶液。光源为CHFHQ型高亮度氙灯光源(北京畅拓科技有限公司提供),光束通过WDG30光栅单色仪获得不同波长下的单色光并照在工作电极上,用恒电位仪控制电极电势为0.2 V,用计算机采集并记录光电流。
2结果与讨论
2.1EDA加入量对ZnO纳米棒阵列形貌的影响
为用计算机采集到的320~440 nm波长单色光照射下的瞬态光电流图,在所测波长范围内,所有膜电极的光电流都比较稳定,且在390 nm处产生最大的光电流响应。 分别为Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构阵列膜电极的瞬态光电流图,可以看出,2种 Sb2S3/ZnO膜电极的光电流响应均已拓展至760 nm处,并且在490 nm处产生了最大的光电流响应;同时,ZnO纳米棒上生长纳米棒和Sb2S3/ZnO分级壳核结构膜电极的最高光电流均分别大于单纯的ZnO纳米棒和Sb2S3/ZnO纳米棒壳核结构的最高光电流。原因可能是ZnO纳米棒上纳米棒的生长致使分级结构的比表面积大大增加,陷光作用增强,同时光生电子在分级结构中的传输通道更多、更直接,从而获得更高的光生电流。
Sb2S3纳米粒子之所以能够敏化ZnO是由Sb2S3和ZnO的能级结构决定的。Sb2S3和ZnO的能级位置[2829]如图7所示,利用Sb2S3对ZnO进行敏化,即将窄禁带半导体包覆在宽禁带半导体上,可以利用窄禁带半导体材料在吸光范围上的优势,增加壳核结构的吸收波长范围,同时构筑的壳核结构会形成一种梯度能级结构[30],能够迅速将电子和空穴分离并传输到壳核结构的不同区域,减少电子、空穴复合的发生,进而极大地增加光捕获能力和吸收效果。
3结论
采用电化学沉积法在ITO导电玻璃上制备了ZnO纳米棒和ZnO纳米棒上生长纳米棒微纳分级结构,利用化学浴沉积法沉积Sb2S3纳米粒子,制备了Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒的分级壳核结构。光电化学测试表明,Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构的光电流明显高于Sb2S3/ZnO纳米棒壳核结构。ZnO纳米棒上二级纳米棒的生长使分级结构的比表面积大大增加,陷光作用明显增强。同时,该分级结构可以吸附更多的Sb2S3纳米粒子,为后期杂化太阳电池效率的大幅提升提供了理论基础和保障。
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2016年2月Journal of Hebei University of Science and TechnologyFeb. 2016
关键词:光电化学;Sb2S3纳米粒子;ZnO纳米棒;微纳分级结构;壳核结构
中图分类号:O649文献标志码:A
Photoelectrochemical properties of hierarchical ZnO micronanostructure sensitized with Sb2S3 nanoparticles[J].Journal of Hebei University of Science and Technology,2016,37(1):2632.Photoelectrochemical properties of hierarchical ZnO micro
nanostructure sensitized with Sb2S3 nanoparticles
GUO Zhimin1, HAO Yanzhong1,2, PEI Juan2, SUN Bao2, LI Yingpin2
(1.School of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, China; 2.School of Science, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, China)
Abstract:By using electrochemical deposition method, and assisted with additions of PEG400 and EDA, wellaligned ZnO nanorods and hierarchical ZnO micronanostructure are fabricated directly on indium doped tin oxide coated conducting glass (ITO) substrate. The shellcore Sb2S3/ZnO nanorod structure and the shellcore hierarchical Sb2S3/ZnO micronanostructure are prepared by chemical bath deposition method. SEM, XRD, UVVis and photocurrent test are used to characterize the morphology, nanostructures and their photoelectrochemical properties. The studies show that the photocurrent on the array membranes with shellcore hierarchical Sb2S3/ZnO micronanostructure is apparently higher than that with shellcore Sb2S3/ZnO nanorods array.
Keywords: photoelectrochemistry; Sb2S3 nanoparticles; ZnO nanorods; micronano hierarchical structure; shellcore nanostructure
一维ZnO纳米半导体材料提供了直接有序的电荷传输通道,提高了光生电荷的分离效率,在太阳电池电极材料方面得到了广泛应用[18]。近年来,人们通过电化学沉积法[911]、水热/溶剂热法等[1213]相继合成了ZnO纳米棒,ZnO纳米棒的微纳分级结构[1416]因高的比表面积和多电子传输通道等优点吸引了很多研究者的关注。XU等[17]利用两步电化学沉积方法制备了ZnO纳米棒分级结构,产品展现出优良的光电性能。王玉辉[18]通过低温溶液法制备的毛笔状ZnO纳米棒分级结构具有很好的紫外发光性能、较高的结晶质量及较低的缺陷密度。ZnO微纳分级结构在太阳电池方面也已经得到了应用。例如:SHI等[19]基于ZnO分级结构制备的染料敏化太阳电池光电转换效率达到了6.42%;ZHENG等[20]利用化学浴沉积法制备的ZnO纳米棒分级结构组成的杂化太阳电池的效率相对于单纯的ZnO纳米棒提高了32.7%。Sb2S3作为一种直接带隙的半导体材料,其能带间隙为1.7~1.8 eV[2122],适合作为敏化剂用于太阳电池的电极材料。Sb2S3量子点作为敏化剂及光吸收材料在制备固态染料敏化太阳电池[2324]、无机薄膜太阳电池[25]及杂化太阳电池[2627]方面得到了重要应用。
河北科技大学学报2016年第1期郭志敏,等:Sb2S3纳米粒子敏化ZnO微纳分级结构的光电化学性能本文在电化学方法制备ZnO纳米棒和ZnO纳米棒上生长纳米棒微纳分级结构的基础上,采用化学浴沉积法沉积Sb2S3 纳米粒子,制备了Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构,并对其光电化学性能进行了表征测试。 1实验过程
1.1电化学法制备ZnO纳米棒阵列膜
电化学沉积采用三电极体系的电解池,工作电极为洁净的ITO导电玻璃,对电极为Pt电极,参比电极为饱和甘汞电极,在油浴恒温70 ℃的条件下采用恒电位模式电沉积1.5 h。具体过程如下:在0.012 5 mol/L,15 mL的Zn(NO3)2水溶液中加入30 μL聚乙二醇,于-1.1 V恒定电势下电沉积3~5 min制备种子层,然后向沉积液中加入8~20 μL的EDA,继续沉积1.5 h,制备高度取向的ZnO纳米棒阵列。将得到的产物用去离子水和无水乙醇交替冲洗,自然干燥,之后于马弗炉中400 ℃温度下煅烧1 h,即可得到结晶良好的ZnO纳米棒阵列膜。
1.2 ZnO纳米棒上生长纳米棒微纳分级结构阵列膜的制备
以沉积有ZnO纳米棒阵列的ITO导电玻璃为工作电极,二次电沉积得到ZnO纳米棒上生长纳米棒微纳分级结构。电解液配制如下:在磁力搅拌器不断搅拌下,向15 mL、浓度为0.025 mol/L的Zn(NO3)2水溶液中以微量注射器加入氨水,溶液开始变浑浊,继续缓慢加入氨水,直至溶液逐渐变为澄清,二次电沉积的电解液每次沉积前新鲜配制。沉积电势为-1.03 V,沉积时间为0.5 h。将沉积所得的产物用去离子水和无水乙醇交替冲洗,并于烘箱中干燥。热处理过程中将沉积有样品的ITO导电玻璃在N2气氛中于400 ℃退火1 h,再自然冷却至室温。
1.3壳核式Sb2S3/ZnO纳米棒、壳核式Sb2S3/ZnO纳米棒上生长纳米棒分级结构的制备
采用化学浴沉积法制备Sb2S3/ZnO壳核式纳米结构。沉积液配制如下:将0.65 g的SbCl3加入2.5 mL丙酮中溶解,加入1 mol/L 的Na2S2O3水溶液25 mL,搅拌均匀,最后加入二次水,使溶液总体积为100 mL。将沉积有ZnO纳米棒和ZnO纳米棒上生长纳米棒分级结构的ITO导电玻璃基底垂直浸入上述溶液中,于10 ℃下反应1 h。沉积结束后,将沉积有样品的ITO导电玻璃用二次去离子水冲洗数次,并在烘箱中干燥1 h。最后,在N2保护的管式炉中于320 ℃煅烧1 h,即可得到壳核式Sb2S3/ZnO纳米棒阵列和壳核式Sb2S3/ZnO纳米棒上生长纳米棒的分级结构阵列。
1.4表征及光电性能测试
采用日本HITACHI公司的S4800I型发射场扫描电镜(SEM)观察阵列膜的形貌和尺寸,采用日本Rigaku公司的D/MAX2500 X射线衍射仪检测阵列膜的晶型和结构,采用日本日立公司的U3900型紫外可见吸收光谱仪对样品的光吸收范围进行测定。
光电化学测试在三电极体系中进行,支持电解质为0.1 mol/L的KSCN溶液。光源为CHFHQ型高亮度氙灯光源(北京畅拓科技有限公司提供),光束通过WDG30光栅单色仪获得不同波长下的单色光并照在工作电极上,用恒电位仪控制电极电势为0.2 V,用计算机采集并记录光电流。
2结果与讨论
2.1EDA加入量对ZnO纳米棒阵列形貌的影响
为用计算机采集到的320~440 nm波长单色光照射下的瞬态光电流图,在所测波长范围内,所有膜电极的光电流都比较稳定,且在390 nm处产生最大的光电流响应。 分别为Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构阵列膜电极的瞬态光电流图,可以看出,2种 Sb2S3/ZnO膜电极的光电流响应均已拓展至760 nm处,并且在490 nm处产生了最大的光电流响应;同时,ZnO纳米棒上生长纳米棒和Sb2S3/ZnO分级壳核结构膜电极的最高光电流均分别大于单纯的ZnO纳米棒和Sb2S3/ZnO纳米棒壳核结构的最高光电流。原因可能是ZnO纳米棒上纳米棒的生长致使分级结构的比表面积大大增加,陷光作用增强,同时光生电子在分级结构中的传输通道更多、更直接,从而获得更高的光生电流。
Sb2S3纳米粒子之所以能够敏化ZnO是由Sb2S3和ZnO的能级结构决定的。Sb2S3和ZnO的能级位置[2829]如图7所示,利用Sb2S3对ZnO进行敏化,即将窄禁带半导体包覆在宽禁带半导体上,可以利用窄禁带半导体材料在吸光范围上的优势,增加壳核结构的吸收波长范围,同时构筑的壳核结构会形成一种梯度能级结构[30],能够迅速将电子和空穴分离并传输到壳核结构的不同区域,减少电子、空穴复合的发生,进而极大地增加光捕获能力和吸收效果。
3结论
采用电化学沉积法在ITO导电玻璃上制备了ZnO纳米棒和ZnO纳米棒上生长纳米棒微纳分级结构,利用化学浴沉积法沉积Sb2S3纳米粒子,制备了Sb2S3/ZnO纳米棒壳核结构和Sb2S3/ZnO纳米棒上生长纳米棒的分级壳核结构。光电化学测试表明,Sb2S3/ZnO纳米棒上生长纳米棒分级壳核结构的光电流明显高于Sb2S3/ZnO纳米棒壳核结构。ZnO纳米棒上二级纳米棒的生长使分级结构的比表面积大大增加,陷光作用明显增强。同时,该分级结构可以吸附更多的Sb2S3纳米粒子,为后期杂化太阳电池效率的大幅提升提供了理论基础和保障。
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2016年2月Journal of Hebei University of Science and TechnologyFeb. 2016