Carbon Nanotubes with Titanium Nitride as a Low-Cost Counter-Electrode Material for Dye-Sensitized Solar Cells
Carbon Nanotubes with Titanium Nitride as a Low-Cost Counter-Electrode Material for Dye-Sensitized Solar Cells
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DOI：
10.1002/anie.201000659
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Shen, Pan-wen
中科院分区：
文献类型：
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作者：
Li, Guo-ran;Wang, Feng;Shen, Pan-wen
染料敏化太阳能电池是一种很有前途的低成本清洁能源转换器件。[1-4]在染料敏化太阳能电池的发展中，关键的挑战包括展示高效率和制造的规模化。[3]作为器件中的传统对电极材料，铂是目前最昂贵的材料之一，对其大规模应用是一个负担。[3，5]此外，半导体电极和电解液的持续改进对对电极性能提出了更高的要求。[5，6]因此，开发低成本、无铂、转换效率相对较高的对电极材料是直接序列太阳能电池发展的必然趋势。DSC中的对电极促进电子从外部电路向氧化还原电解液的转移，并催化三碘离子的还原。因此，人们迫切需要具有高电导率和优异电催化活性的对电极材料。然而，要同时满足这两方面的要求通常并不容易。通常，小颗粒由于具有较大的比表面积而具有较高的电催化活性，但由于丰富的晶界和缺陷，它们也降低了电子传输效率。[8]根据以往的研究，碳纳米管(CNTs)、[9，10]炭黑、[11]介孔碳、[12]活性碳、[13]富勒烯[14]和导电聚合物[14，15]等碳材料通常表现出良好的性能，这是因为这些材料的大比表面积可以弥补碳固有的低电催化活性。Grätzel和他的同事最近在具有良好导电性的PEN/ITO薄膜上电化学沉积CoS纳米颗粒，以获得具有显著电池稳定性的高性能无铂对电极。[16]为了将高导电性和卓越的电催化活性结合在一种材料中，我们提出了一种替代设计，通过构建快速电子传输网络和在电子路径上创建高活性位置来制备低成本的无铂对电极材料。由于多壁碳纳米管的弹道输运和扩散输运并存以及管状结构，可以认为它是一种快速的电子传输网络。此外，碳纳米管对三碘离子的还原具有一定的电催化活性，[9-10]，其良好的力学性能也有助于电极膜的形成。[18]因此，碳纳米管是构建快速电子传输网络的合适基质材料。在高效电催化剂方面，由于金属氮化物的电子结构与贵金属的相似，氮化钛(TiN)对三碘离子的还原表现出很高的本征电催化活性。[19，20]由高度有序的锡纳米管阵列组成的DSSC表现出与典型的铂对电极相当的性能。[20]然而，由于纳米粒子之间的电子传输效率较低，单独的锡纳米颗粒膜电极具有较低的填充因子(FF)。[20]此外，将碳纳米管的导电路径引入锡中可以提高锡的导电性和电容。[21]在这里，我们证明了低成本的锡-碳纳米管阵列电极具有较低的填充因子(FF)。将TiN纳米颗粒锚定在碳纳米管网络上，可以同时提供高导电性和优异的电催化活性。TiN-CNTs是由TiOSO4在碳纳米管上热解，然后在氨气气氛中氮化得到的。X-射线衍射仪测试结果表明，As-…
Dye-sensitized solar cells (DSSCs) are promising candidates for low-cost and clean energy conversion devices.[1–4] In the development of DSSCs, key challenges include the demonstration of high efficiency and scale-up of fabrication.[3] As the conventional counter-electrode material in the devices, platinum, is a burden for large-scale applications of DSSCs because it is one of the most expensive materials available.[3, 5] Furthermore, the sustaining improvement of semiconductor electrode and electrolyte poses higher demand on counterelectrode performance.[5, 6] Therefore, it is necessary to develop low-cost and platinum-free counter-electrode materials with relatively high conversion efficiency for DSSCs. The counter electrode in DSSCs promotes the electron translocation from the external circuit back to the redox electrolyte, and catalyzes the reduction of triiodide ions. Therefore, counter-electrode materials of high electrical conductivity and superior electrocatalytic activity are highly desired.[5, 7] However, it is usually not easy to meet the both above requirements simultaneously. Generally, small particles provide high electrocatalytic activity owing to the large surface area, but they also lower electron transport efficiency owing to the abundant grain boundaries and defects.[8] According to previous studies, carbonaceous materials, such as carbon nanotubes (CNTs),[9, 10] carbon black,[11] mesoporous carbon,[12] activated carbon,[13] fullerene,[14] and electroconductive polymers,[14, 15] generally show good performance because the large surface area of the materials can redress the low intrinsic electrocatalytic activity of carbon. Grätzel and co-workers recently deposited electrochemically CoS nanoparticles on PEN/ITO film with good electrical conductivity to obtain a high-performance platinum-free counter electrode with a remarkable cell stability.[16] To combine both high electrical conductivity and superior electrocatalytic activity in one material, we propose an alternative design for the fabrication of low-cost and platinum-free counter-electrode materials by constructing a fast electron-transport network and creating highly active sites on the electron pathway. Multi-walled carbon nanotubes can be considered as a fast electron-transport network because of the coexistence of ballistic and diffusive transport [17] and the tubular morphology.[10] Furthermore, CNTs possess electrocatalytic activity for the reduction of triiodide ions to a certain extent,[9–10] and their good mechanical properties are also helpful for the formation of electrode film.[18] Therefore, CNTs are suitable matrix material for constructing a fast electron-transport network. Regarding the highly efficient electrocatalyst, titanium nitrides (TiN) demonstrate high intrinsic electrocatalytic activity for the reduction of triiodide ions owing to the similarity of the electronic structure of the metal nitrides to that of the noble metals.[19, 20] A DSSC composed of the highly ordered TiN nanotube arrays shows comparable performance with typical Pt counter electrode.[20] However, TiN nanoparticle film electrode alone has lower fill factor (FF) owing to the poor electron transport efficiency across nanoparticles.[20] Furthermore, the introduction of conducting paths of CNTs into TiN can improve electrical conductivity and capacitance of TiN.[21] Herein, we demonstrate that low-cost TiN-CNTs, fabricated by anchoring TiN nanoparticles on the CNTs network, can provide simultaneous high electrical conductivity and superior electrocatalytic activity.TiN-CNTs were prepared by thermal hydrolysis of TiOSO4 on CNTs and subsequent nitridation in an ammonia atmosphere. XRD results indicate that the as …