Macroscopic 3D Nanographene with Dynamically Tunable Bulk Properties
Macroscopic 3D Nanographene with Dynamically Tunable Bulk Properties
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DOI：
10.1002/adma.201202289
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发表时间：
2012-09-25
影响因子：
29.4
通讯作者：
Baumann, Theodore F.
中科院分区：
文献类型：
--
作者：
Biener, Juergen;Dasgupta, Subho;Baumann, Theodore F.
表面占主导地位的块体材料提供了独特的机会，动态控制其物理块体性质的改性，通过其表面通过界面现象。[1，2]然而，产生相当大的效果需要表面原子占原子总数的很大一部分。这一要求限制了表面占主导地位的块体材料的技术潜力，因为表面原子超过10%的结构通常不是很稳定，并且往往会通过粗化降低其表面能。[3]在这里，石墨烯是一个例外-它结合了高达2630 m2 g-1的非常高的表面积与sp 2键合碳的二维（2D）结构固有的化学和热稳定性。这使得石墨烯成为用于实现稳定的可膨胀表面积块体材料的令人感兴趣的构建块。石墨烯还具有许多其他显着的特性，[4，5]包括极高的电导率和热导率，以及卓越的机械强度和弹性，原则上，这些都应该通过界面现象进行动态控制。因此，石墨烯基块体材料具有巨大的技术潜力，超出了它们在能量存储和传感领域的明显应用[6]，到目前为止，这已经推动了使用石墨烯和氧化石墨烯的各种“自下而上”组装方法向3D架构的发展。[7-10]然而，尽管最近在石墨烯和氧化石墨烯（GO）片的大规模生产方面取得了进展，[11，12]石墨烯对于石墨烯基块体材料的大规模制造来说仍然过于昂贵。此外，通过聚集损失表面积仍然是一个挑战。[10]在这篇文章中，我们描述了一种“自上而下”的策略，通过从由无定形碳和石墨纳米片组成的网络中控制碳原子的去除，从低成本聚合物衍生的碳泡沫中制造可大规模生产的石墨烯基块状材料（图1a）。这种方法本质上是廉价的（每千克材料几美元），可扩展的，并产生机械坚固的厘米级单片样品（图1 B），几乎完全由单层石墨烯纳米片的互连网络组成。这种3D纳米石墨烯（3D-NG）块体材料的比表面积（高达3000 m 2 g− 1，参见支持信息中的图S1）与独立石墨烯层相当，但它具有开放的大孔隙率（图1 c），有助于整个块体的快速质量传输。尽管3D-NG具有高表面积，但其密度相对较高（约200 kg m− 3），这使得该材料具有惊人的耐用性。例如，纳米力学测试显示模量E为300-1000 MPa，迈耶硬度为20-100 MPa（支持信息中的图S3）。后者表明承重能力为200 kg cm− 2，这对于由100%表面原子组成的材料来说是惊人的高。3D-NG制造的起点是通过有机溶胶-凝胶化学制备的大孔碳网络。溶胶凝胶法涉及有机前体的催化聚合以产生高度交联的有机凝胶，然后在环境条件下干燥，随后在惰性气氛中通过热解转化为碳。[13]这种方法的重要优点是，凝胶可以被浇铸成任何所需的尺寸或形状，并且可以通过反应条件来控制结构特征，例如孔结构和韧带尺寸。在这里报道的工作中，我们开发了产生孔径的反应条件...
Surface-dominated bulk materials provide the unique opportunity to dynamically control their physical bulk properties by modification of their surfaces through interfacial phenomena.[1, 2] Generating a sizable effect, however, requires that surface atoms constitute a large fraction of the total number of atoms. This requirement limits the technical potential of surface-dominated bulk materials, as structures with more than 10% surface atoms are typically not very stable and tend to reduce their surface energy by coarsening.[3] Here, graphene is an exception—it combines a very high surface area of up to 2630 m 2 g− 1 with the chemical and thermal stability intrinsic to the two-dimensional (2D) structure of sp 2-bonded carbon. This makes graphene an interesting building block for realization of stable ultrahigh surface area bulk materials. Graphene also possesses many other remarkable properties,[4, 5] including extremely high electrical and thermal conductivities, and exceptional mechanical strength and elasticity, which, in principle, should all be amenable to dynamic control via interfacial phenomena. As such, graphene-based bulk materials hold great technological potential beyond their obvious applications in the fields of energy storage and sensing [6] that so far have driven the development of various “bottom up” assembly approaches using graphene and graphene oxide towards 3D architectures.[7–10] However, despite recent progress in large-scale production of graphene and graphene oxide (GO) sheets,[11, 12] graphene is still prohibitively expensive for large-scale manufacturing of graphenebased bulk materials. In addition, loss of surface area through aggregation remains a challenge.[10] In this Communication, we describe a “top down” strategy to fabricate mass-producible graphene-based bulk materials from low-cost polymer-derived carbon foams through the controlled removal of carbon atoms from a network composed of both amorphous carbon and graphite nanoplatelets (Figure 1a). This approach is inherently inexpensive (a few dollars per kilogram of the material), scalable, and yields mechanically robust, centimeter-sized monolithic samples (Figure 1 b) that are composed almost entirely of interconnected networks of singlelayer graphene nanoplatelets. The specific surface area (up to 3000 m 2 g− 1, see Figure S1 in the Supporting Information) of this 3D nanographene (3D-NG) bulk material is comparable to that of a freestanding graphene layer, yet it has an open macroporosity (Figure 1 c) that facilitates rapid mass transport throughout the bulk. Despite its high surface area, 3D-NG has a relatively high density (∼ 200 kg m− 3), which makes the material surprisingly robust. For example, nanomechanical tests revealed a modulus E of 300–1000 MPa and a Meyer hardness of 20–100 MPa (Figure S3 in the Supporting Information). The latter suggests a weight-bearing capacity of 200 kg cm− 2, which is surprisingly high for a material that consists of 100% surface atoms.The starting point for fabrication of 3D-NG is a macroporous carbon network prepared by organic sol-gel chemistry. The solgel process involves the catalyzed polymerization of organic precursors to yield a highly cross-linked organic gel that is then dried under ambient conditions and subsequently converted to carbon through pyrolysis in an inert atmosphere.[13] The important advantages of this approach are that the gel can be cast into any desired size or shape, and that architectural features, such as the pore structure and the ligament size, can be controlled through the reaction conditions. In the work reported here, we developed reaction conditions that yield pore sizes …