Patterned CNT arrays for the evaluation of oxygen reduction activity by SECM.
Patterned CNT arrays for the evaluation of oxygen reduction activity by SECM.
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DOI：
10.1002/cphc.200900744
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发表时间：
2010-01
期刊：
影响因子：
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通讯作者：
Stefanie Schwamborn;Leonard Stoica;Xingxing Chen;Wei Xia;S. Kundu;M. Muhler;W. Schuhmann
中科院分区：
文献类型：
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作者：
Stefanie Schwamborn;Leonard Stoica;Xingxing Chen;Wei Xia;S. Kundu;M. Muhler;W. Schuhmann
由于碳纳米管（CNT）的高表面积和它们的上级机械以及电子性质，碳纳米管（CNT）例如被用作过滤器和吸附剂、纳米电子器件和（生物）化学传感器。[1]碳纳米管的应用也已扩展到电催化领域，利用其高表面积，使高催化剂负载。[2，3]此外，它们表现出特定的金属-载体相互作用，与g-氧化铝或碳相比，可以导致活性增强。[3，4]例如，CNT可以在高覆盖率（< 95%）下增强Pt颗粒的分散，而Pt颗粒在相同条件下倾向于在玻璃碳（GC）上聚结。[5]此外，它们可以促进电子转移反应，并且它们对例如氧还原反应（ORR）表现出固有的电催化活性。[5-8]通过在CNT表面引入氮，可以进一步增强它们对O2还原的催化活性。[9-13]因此，CNT被认为是用于例如燃料电池中的氧去极化阴极的有前景的材料。[14-17]为了评估CNT的固有局部催化活性以及它们作为用作ORR的电催化剂的金属纳米颗粒的载体的性质，可以应用扫描电化学显微镜（SECM）。[18]原则上，有序的CNT微结构可以按照两种不同的策略合成。一方面，预生长的CNT可以在电场[19，20]、流体通道[21]中组装，并通过“极性引导组装”组装。[22另一方面，CNT图案可以通过使用局部限制的催化剂点的金属催化化学气相沉积（CVD）直接生长。[24-28]迄今为止，已经使用光刻法来获得良好限定的掩模，通过该掩模可以通过电子束蒸发[24]或通过挥发性催化剂和CNT前体的气相混合物的CVD来沉积Fe催化剂。[27]催化剂也可以使用微接触印刷来印刷。[25]这些技术使得催化剂以及随后生长的CNT能够快速且可控地图案化。在CVD工艺期间CNT的这种直接组装的一个益处是制造某些直径的垂直对准CNT
Due to their high surface area and their superior mechanical as well as electronic properties, carbon nanotubes (CNTs) are applied, for example, as filters and sorbents, nanoelectronic devices and (bio) chemical sensors.[1] The implementation of CNTs has also been extended to the field of electrocatalysis, taking advantage of their high surface area that enables high catalyst loadings.[2, 3] Furthermore, they exhibit specific metal–support interactions that can lead to an activity enhancement compared to g-alumina or carbon.[3, 4] For example, CNTs can enhance the dispersion of Pt particles at high coverages (< 95%), while Pt particles tend to coalescence on glassy carbon (GC) under the same conditions.[5] Moreover, they can promote electron transfer reactions and they exhibit an inherent electrocatalytic activity towards for example, the oxygen reduction reaction (ORR).[5–8] Their catalytic activity for O2 reduction can be enhanced even further by incorporation of nitrogen at the CNT surface.[9–13] Therefore, CNTs are considered to be promising materials for oxygen depolarized cathodes in fuel cells, for example.[14–17]In order to evaluate the inherent local catalytic activity of CNTs as well as their properties as support for metal nanoparticles used as electrocatalysts for the ORR, scanning electrochemical microscopy (SECM) can be applied.[18] In principle, ordered CNT microstructures can be synthesized following two different strategies. On the one hand, pre-grown CNTs can be assembled in electric fields [19, 20], fluidic channels [21] and by “polarity-guided assembly”.[22, 23] On the other hand, CNT patterns can be directly grown by metal-catalyzed chemical vapour deposition (CVD) using locally confined catalyst spots.[24–28] Hitherto, photolithography has been used to obtain well-defined masks through which the Fe catalyst can be deposited by electron beam evaporation [24] or by CVD of a gas phase mixture of volatile catalyst and CNT precursor.[27] The catalyst can also be printed using microcontact printing.[25] These techniques enable fast and controllable patterning of the catalyst and consequently of the subsequently grown CNTs. One benefit of this direct assembly of CNTs during the CVD process is the fabrication of vertically aligned CNTs of certain diameters