Joule Heating-Driven Transformation of Hard-Carbons to Onion-like Carbon Monoliths for Efficient Capture of Volatile Organic Compounds

Abstract

Soft graphitizable carbon-based multifunctional nanomaterials have found versatile applications ranging from energy storage to quantum computing. In contrast, their hard-carbon analogues have been poorly investigated from both fundamental and application-oriented perspectives. The predominant challenges have been (a) the lack of approaches to fabricate porous hard-carbons and (b) their thermally nongraphitizable nature, leading to inaccessibility for several potential applications. In this direction, we present design principles for fabrication of porous hard-carbon-based nanostructured carbon florets (NCFs) with a highly accessible surface area (∼936 m2/g), rivalling their soft-carbon counterparts. Subjecting such thermally stable hard-carbons to a synergistic combination of an electric field and Joule heating drives their transformation to free-standing macroscopic monoliths composed of onion-like carbons (OLCMs). This represents the first such structural transformation observed in sp2-based hard-carbon NCFs to sp2-networked OLCMs. Micro-Raman spectroscopy establishes the simultaneous increase in the intensity of D-, 2D-, and D + G-bands at 1341, 2712, and 2936 cm–1 and is correlated to the reorganization in the disordered graphitic domains of NCFs to curved concentric nested spheres in OLCMs. This therefore completely precludes the formation of a nanodiamond core that has been consistently observed in all previously reported OLCs. The Joule heating-driven formation of OLCMs is accompanied by ∼5700% enhancement in electrical conductivity that is brought about by the fusion of outermost graphitic shells of OLCs to result in monolithic OLC structures (OLCMs). The porous and inter-networked OLCMs exhibit an excellent adsorption-based capture of volatile organic compounds such as toluene at high efficiencies (∼99%) over a concentration range (0.22–1.86 ppm) that is relevant for direct applications such as smoke filters in cigarettes.

Characterizing Joule Heating Effects on Single Suspended Carbon Fibers: Calculating the Temperature Coefficient of Resistance for Localized Carbon Nanotube Growth

“…46 Additionally, subjecting glassy carbon to temperatures exceeding 2000 °C resulted in the formation of porous and buckled structures, including onion-like structures, graphene-like layers, and fullerene-like particles. 47,48 The emergence of these ordered structures from a disordered carbon atom distribution leads to an enlargement of carbon layers and voids. The newly formed porous structures generate internal tension along the CF, causing it to swell.…”

Phonon-Engineered Hard-Carbon Nanoflorets Achieving Rapid and Efficient Solar-Thermal Based Water Evaporation and Space-Heating

“…Given the unique open-ended morphology and high surface area of NCF, our lab has previously studied its utility as electrochemical energy storage electrodes, adsorbents for heavy metal ions and for enhancing the efficiency of thermal receivers. ,− In this context, this report exclusively focuses on the solar-thermal conversion ability of NCF and demonstrates the versatility of NCF coating for various applications ranging from solar-steam generation and active space-heating. Importantly, a detailed structure–property-application correlation of the multifunctional NCF is presented, which was hitherto unknown.…”

Interface Engineered Hard-Carbons as Subsurface Hydrogen Reservoir for Accelerated and Highly Selective Olefin Hydrogenation with Favorable Sustainability Metrics

“…The open-ended, well-separated lamellae of NCF were prepared using dendritic fibrous nano silica (DFNS) as a template following an established protocol (refer to Supporting Information for details of preparation method). − The as-prepared NCF was used as a catalyst support to prepare Pt-based nanostructured catalysts in two different approaches, PON and PIN. To fabricate the PON catalyst, 10 mg of NCF was mixed with 50 mL of 0.1 mM aqueous solution of chloroplatinic acid hydrate and stirred continuously at approximately 600 rpm for 5–6 h. The metal-loaded NCF suspension was repeatedly washed with distilled water for 5–6 times and dried at 80 °C in a hot-air oven, followed by supercritical CO 2 drying overnight.…”