384739 Bi-Continuous, Ultra-Large-Pore Carbons By Template-Replica Co-Assembly

Tuesday, November 18, 2014: 12:50 PM
International 3 (Marriott Marquis Atlanta)
Zheng Tian and Mark A. Snyder, Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA

Among classes of mesoporous materials bearing high surface area, three-dimensionally ordered pore topology, and large pore volumes, ordered mesoporous carbons (OMCs) have attracted specific interest due to their low cost, thermal and physicochemical stability and electrical conductivity, properties that make them attractive for applications as diverse as electrodes in energy conversion and storage devices, supercapacitors, catalysts, and adsorbents.  So-called ‘soft-templating’ or ‘direct’ strategies that exploit the self-assembly phase behavior of copolymer surfactants as templates and polymerizable carbon precursors by evaporation induced self-assembly (EISA) can be used to realize ordered mesoporous carbons. While such processes enjoy scalability, owing to their reliance on ‘one-pot’ solution phase thermodynamics, they do face several critical drawbacks including the cost of template sacrifice, pore shrinkage, limits on carbon source variability and thus on the tunability of intrinsic carbon properties, and difficulties in realizing stable, ultra-large pore topologies for applications requiring access by bulk molecules or ease of solution/solvent infiltration.

While the alternative ‘hard’-templating approach provides promise for addressing these drawbacks, it is generally discounted due to its multi-step nature and possible reliance on surfactant-templated fabrication of ordered mesoporous silica precursors as template materials.  Inspired by the simplicity of ‘one-pot’ soft-templating strategies, this talk will highlight progress toward realizing a facile ‘one-pot’ hard-templating method capable of deriving bi-continuous, three-dimensionally ordered porous carbon thin films and powders. Specifically, we will show how pre-formed size tunable silica nanoparticles (ca. 20-50 nm) can be co-assembled from aqueous solutions with a carbon source into powders and thin films bearing a three-dimensionally ordered, bi-continuous mesopore topology. 

We will describe the pseudo-phase behavior governing this co-assembly, the order-disorder transition and particle-particle spacing of which is modulated by adsorption of the carbon source to the assembling silica nanoparticle template and its concomitant modulation of the particle-particle interactions.  Mechanistic insight into the formation of these materials will employ comprehensive analysis spanning HPLC adsorption studies, nitrogen and argon physisorption, XPS, cyclic voltammetry, and high-resolution electron microscopy.  We exploit the high surface area, apparently tunable sp2-hybridized carbon content, and facile and low-cost ‘one-pot’ synthesis of these ordered mesoporous materials for applications spanning low-cost electrodes in both supercapacitor and dye-sensitized solar cell applications, in both cases showing promising performance relative to laboratory and literature standards.

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