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Tunability of Aromatic Carbon Materials

Creative Commons 'BY-NC-ND' version 4.0 license
Abstract

Carbon is both abundant and functionally versatile due to the variability of orbital hybridization of carbon atoms forming linear, planar, and tetrahedral bonds leading to many allotropes. Different allotropes exhibit different physical properties such as electrical conductivity, surface area, and surface chemistry. The work presented here focuses on aromatic carbon materials and examines the tunability of physical properties, molecular to macroscopic structural formation, and importance in environmental applications, specifically soot pollution mitigation and next-generation single atom catalysis.

First, scanning tunneling microscopy (STM) experiments explore the intermolecular interactions of coronene (C12H24), a polycyclic aromatic hydrocarbon hypothesized to play a key role in incipient soot formation. The hazardous impacts of incipient soot – including lengthy suspension in the earth’s atmosphere and deep penetration into human respiratory systems – may be circumvented through an improved understanding of soot formation. Observations of coronene clusters reveal structures strikingly similar to recent models of clusters hypothesized to initiate soot formation. In contrast to mature soot, cluster surfaces are composed primarily of molecular edges. These findings have important implications for how additional molecules attach and become incorporated into growing soot particles.

Second, a first principles approach is used to identify how the local molecular environment on a graphene support can be used to stabilize a single platinum atom catalyst. Inspired by visions of achieving ultimate cost-effectiveness and performance, a single atom catalyst represents the most efficient use of precious metals while concurrently offering the potential for high chemical activity. Density functional theory results indicate that pyridinic nitrogen-doped graphene is a promising candidate to support a single Pt atom acting as a catalyst that is resistant to poisoning and enhances carbon monoxide oxidation efficiency. Experimental efforts demonstrate a pathway towards developing these supports, using bicontinuous interfacially jammed emulsion gels as templates for the growth of three-dimensional, porous graphene. STM, X-ray photoelectron spectroscopy, and Raman spectroscopy characterize the resultant architectures, relating nanoscale observations to macroscale properties such as specific surface area and mechanical strength.

This work – examining aromatic carbon materials – demonstrates how surface science techniques can unravel self-assembly and the physics that shape our macroscale environment.

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