High‐Performance Nanostructured Membrane Electrode Assemblies for Fuel Cells Made by Layer‐By‐Layer Assembly of Carbon Nanocolloids
High‐Performance Nanostructured Membrane Electrode Assemblies for Fuel Cells Made by Layer‐By‐Layer Assembly of Carbon Nanocolloids
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DOI：
10.1002/adma.200701219
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发表时间：
2007-11
影响因子：
29.4
通讯作者：
M. Michel;A. Taylor;R. Sekol;P. Podsiadlo;P. Ho;N. Kotov;L. Thompson
中科院分区：
文献类型：
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作者：
M. Michel;A. Taylor;R. Sekol;P. Podsiadlo;P. Ho;N. Kotov;L. Thompson
正在开发燃料电池，以取代便携式电子设备中的电池和汽车中的内燃机。质子交换膜（PEM）燃料电池商业化面临的主要挑战是成本高和耐久性差。其中一个主要的成本驱动因素是膜电极组件（MEA），它由催化剂、电解质膜和气体扩散层（gdl）组成。提高PEM燃料电池的成本和性能将需要更有效地利用催化剂和减少MEA膜的厚度，这需要优化膜的纳米和亚微米结构。[1-11]最近，层接层组装（LBL）[12]已被用于制备PEM燃料电池的子结构[13-18]，作为平衡不同冲突要求的工具。LBL使导电纳米元件的简单结合、任何复杂几何形状表面的保形涂层、多层膜的高离子含量、纳米级对膜厚度和膜孔隙率的控制成为可能。这些特点使LBL成为燃料电池组装的一项有吸引力的新技术。Liu和同事报道了通过还原Nafion膜表面的Pt前驱体，在MEA中制造了一种电极结合催化剂，Farhat和Hammond使用lbl制成的膜作为阴极和阳极的分离器，并达到了传统炭黑（CB）电极16.5 mWcm -2的功率密度。配体稳定铂纳米粒子的LBL组装也被用于构建三维纳米结构电极，在0.9 V下，其质量比活性为0.11 Amg -1 Pt，用于5层薄膜。[14]不幸的是，这些薄膜没有在实际的燃料电池中进行测试，5层薄膜作为MEA的功能部分有些可疑。LBL薄膜作为屏障层沉积在Nafion膜上，也被认为是直接甲醇燃料电池中减少甲醇交叉的有效方法。通过还原沉淀Pt盐（H2PtCl6）得到了掺杂Pt的聚苯胺(PANI)/聚丙烯酸-共聚丙烯酰胺（PAA-co-PAAm）薄膜，其最大Pt负载为0.3 mgcm -2。采用一种不同的颗粒掺入方法，碳聚合物电极使用聚电解质和市售的胶体分散体构建。电极的电子电导率为2 ~ 4 μ m -1，离子电导率为10 ~ 10 ~ 3 μ m -1。总的来说，尽管该技术具有许多有利的特性，但所生产的PEM和其他燃料电池的性能大大低于传统的CB燃料电池，这可以归因于不理想的组织，例如Pt颗粒[13]的岛状分布和相当低的导电性。在本文中，我们报道了碳纳米管和
Fuel cells are being developed to replace batteries in portable electronic devices and internal combustion engines in automobiles. Key challenges to the commercialization of protonexchange membrane (PEM) fuel cells include high cost and poor durability. One of the primary cost-drivers is the membrane electrode assembly (MEA), which consists of the catalysts, electrolyte membrane, and gas diffusion layers (GDLs). Improving PEM fuel-cell cost and performance will require more efficient utilization of the catalyst and a reduction in the thickness of the MEA membrane, which requires optimization of the nano- and sub-micron structure of the membranes. [1–11] Recently layer-by-layer assembly (LBL) [12] has been used to prepare substructures for PEM fuel cells [13–18] as a tool for balancing different conflicting requirements. LBL makes possible simple incorporation of conductive nanocomponents, conformal coatings of surfaces of any complex geometry, high ionic contents of the multilayers, nanometer-scale control over film thickness, and film porosity. These features make LBL an attractive new technology for fuel-cell assembly. Liu and co-workers reported the fabrication of an electrode-incorporating catalyst in MEA via the reduction of a Pt precursor on the surface of a Nafion membrane, [13] and Farhat and Hammond used LBL-made membranes as a separator of cathode and anode and reached power densities with conventional carbon black (CB) electrodes of 16.5 mWcm –2 . [18] The LBL assembly of ligand-stabilized platinum nanoparticles was also used to build three-dimensional nanostructured electrodes with a mass-specific activity of 0.11 Amg –1 Pt at 0.9 V for a 5 layer film. [14] Unfortunately, these films were not tested in an actual fuel cell and 5 layer films are somewhat questionable as a functional part of MEA. LBL thin films deposited as a barrier layer on a Nafion membrane were also suggested to be effective for the reduction of methanol cross over for direct methanol fuel cells. [15] LBL multilayers of polyaniline (PANI)/poly(acrylic acid)-co-polyacrylamide (PAA-co-PAAm) film doped with Pt by reductive precipitation of a Pt salt (H2PtCl6) yielded a maximum Pt loading of 0.3 mgcm –2 . [18] Using a somewhat different approach for particle incorporation, carbon-polymer electrodes were constructed using polyelectrolytes and commercially available colloidal dispersions. [18] The electrodes exhibited electronic conductivities of 2–4 Scm –1 and ionic conductivities in the range from 10 to 10 –3 Scm –1 . Overall, despite the many favorable characteristics of the technique, the performance of the produced PEM and other fuel cells was substantially below the traditional ones with CB, and this can be attributed to suboptimal organization, such as an islandlike distribution of Pt particles [13] and fairly low conductivities. In this paper we report the use of carbon-nanotube and