Stacked-cup carbon nanotubes for photoelectrochemical solar cells.
Stacked-cup carbon nanotubes for photoelectrochemical solar cells.
复制标题
DOI：
10.1002/anie.200502815
复制
发表时间：
2006-01
影响因子：
--
通讯作者：
Taku Hasobe;S. Fukuzumi;P. Kamat
中科院分区：
文献类型：
--
作者：
Taku Hasobe;S. Fukuzumi;P. Kamat
碳纳米管在光学、电子和催化应用中的有用性促使研究人员合成不同形状和尺寸的碳纳米结构。[1-4]由截头圆锥形石墨烯层组成的叠杯碳纳米管特别令人感兴趣，因为常规碳纳米管由六边形碳网络的无缝圆柱体组成，而叠杯结构提供中空管状形态。[5]这种截头圆锥形态在中空管的外表面和内表面中提供了大部分暴露和反应边缘。这些堆叠杯的内边缘和外边缘的化学功能化或表面改性的可用性在电子和催化应用中开辟了新的途径。[6]较长的堆叠杯通过球磨破碎成较小的单元，因此可接近的活性位点的数量增加。[7]这些较小的堆叠杯单元也被称为纳米桶。沿着管状表面增加的活性区域非常有效地促进了金属纳米颗粒的浸渍。通过利用这一附加特征，碳堆叠杯已成功地用作燃料电池中的支撑件。[8]碳纳米结构的一个有趣的特性是它们的光学响应，以及它们在光能转换器件中的利用。例如，富勒烯表现出丰富的光化学，并在光化学太阳能电池中充当电子穿梭机。[9]它们在提高有机光伏电池的性能方面也发挥着重要作用。另一方面，当受到带隙激发时，半导体碳纳米管经历电荷分离。激子湮灭和电荷分离过程的特征在于瞬态吸收和发射测量。[4，10，11]还努力用半导体改性碳纳米管以用于光电流产生。[12在此，我们呈现了叠杯碳纳米管的光学性质，以及它们的半导体性质在具有高光电转换效率的光电化学电池中产生光电流的有效性（图1）。管状形式的叠杯碳纳米管（称为SCCNT或碳纳米管）的球磨样品是来自日本GSI Creos公司的礼物。通过超声处理30- 60分钟，这些纳米管可以容易地悬浮在有机溶剂如THF中，并且保持悬浮超过24小时。THF中悬浮液的吸收光谱显示出宽吸收，没有特定的吸收峰（图2A中的光谱a）。这些堆叠杯的溶解容易性允许我们进行瞬态吸收光谱测量（见下文）。
The usefulness of carbon nanotubes in optical, electronic, and catalytic applications has prompted researchers to synthesize carbon nanostructures of different shapes and sizes.[1–4] Stacked-cup carbon nanotubes consisting of truncated conical graphene layers are of particular interest because whereas conventional carbon nanotubes are made up of seamless cylinders of hexagonal carbon networks, the stacked-cup structure provides a hollow tubular morphology.[5] This truncated-cone morphology provides a large portion of exposed and reactive edges in the outer and inner surfaces of the hollow tubes. The availability of the inner and outer edges of these stacked-cups to chemical functionalization or surface modification opens up new avenues in electronic and catalytic applications.[6] The longer stacked cups are broken into smaller units by ball milling, and thus the number of accessible active sites is increased.[7] These smaller stacked cup units are also referred to as nanobarrels. The increased active area along the tubular surface facilitates impregnation of metal nanoparticles quite effectively. By making use of this added feature, carbon stacked cups have been successfully used as supports in fuel cells.[8] An interesting property of carbon nanostructures is their optical response, and their utilization in light energy conversion devices. Fullerenes, for example, exhibit rich photochemistry and act as electron shuttles in photochemical solar cells.[9] They also play an important role in improving the performance of organic photovoltaic cells. On the other hand, the semiconducting carbon nanotubes undergo charge separation when subjected to bandgap excitation. The exciton annihilation and charge-separation processes have been characterized by transient absorption and emission measurements.[4, 10, 11] Efforts have also been made to modify the carbon nanotubes with semiconductors for use in photocurrent generation.[12, 13] Herein we present the optical properties of stacked-cup carbon nanotubes, and the effectiveness of their semiconducting properties to generate photocurrent in a photoelectrochemical cell with high photoconversion efficiency (Figure 1).The ball-milled sample of stacked-cup carbon nanotubes (referred to as SCCNTs or carbon nanobarrels) in the tubular form was a gift from GSI Creos corporation, Japan. These nanotubes can be readily suspended in organic solvents, such as THF, by sonication for 30–60minutes, and remain in suspension for more than 24 h. The absorption spectrum of the suspension in THF showed broad absorption with no specific absorption peaks (spectrum a in Figure 2 A). The ease of solubilization of these stacked cups allowed us to carry out transient absorption spectroscopy measurements (see below).