Functional Carbon Materials Derived through Hypergolic Reactions at Ambient Conditions

Abstract

Carbon formation from organic precursors is an energy-consuming process that often requires the heating of a precursor in an oven at elevated temperature. In this paper, we present a conceptually different synthesis pathway for functional carbon materials based on hypergolic mixtures, i.e., mixtures that spontaneously ignite at ambient conditions once its ingredients contact each other. The reactions involved in such mixtures are highly exothermic, giving-off sizeable amounts of energy; hence, no any external heat source is required for carbonization, thus making the whole process more energy-liberating than energy-consuming. The hypergolic mixtures described here contain a combustible organic solid, such as nitrile rubber or a hydrazide derivative, and fuming nitric acid (100% HNO3) as a strong oxidizer. In the case of the nitrile rubber, carbon nanosheets are obtained, whereas in the case of the hydrazide derivative, photoluminescent carbon dots are formed. We also demonstrate that the energy released from these hypergolic reactions can serve as a heat source for the thermal conversion of certain triazine-based precursors into graphitic carbon nitride. Finally, certain aspects of the derived functional carbons in waste removal are also discussed.

Nanocarbon from Rocket Fuel Waste: The Case of Furfuryl Alcohol-Fuming Nitric Acid Hypergolic Pair

“…Furthermore, they show some additional ways of exploiting the released energy from hypergolic reactions that are complementary to the chemical, thermoelectric, or photovoltaic work presented elsewhere [ 15 , 17 , 18 ]. Hence hypergolics not only enables an operationally simple carbon synthesis but also gives off useful energy in the process.…”

“…Recently our group has introduced hypergolic reactions as a new and general synthesis tool towards the formation of a variety of functional carbon materials (nanosheets, crystalline graphite, carbon dots, fullerols, hollow spheres, and nanodiscs) [ 15 , 16 , 17 , 18 , 19 , 20 ]. Hypergolic synthesis presents certain advantages over conventional carbonization methods (pyrolysis, hydrothermal, chemical vapor deposition—CVD) for two main reasons.…”

“…This clearly differentiates from pyrolytic, hydrothermal, or CVD methods that require higher temperature in order to operate synthesis and extract carbon from its precursors (i.e., an energy-consuming process). In fact, we have previously demonstrated that the energy released from hypergolic reactions could be directly converted into useful chemical, thermoelectric, or photovoltaic work [ 15 , 17 , 18 ]. Therefore, hypergolics allows a fast and spontaneous carbon synthesis at ambient conditions in an energy-liberating manner without external stimuli (heat, spark, or mechanical shock).…”

Carbon Nanostructures Derived through Hypergolic Reaction of Conductive Polymers with Fuming Nitric Acid at Ambient Conditions

“…In addition, the non-volatile nature of the solid polymer makes it safer and a much better carbon precursor than the volatile liquid monomer (e.g., polymers tend to provide higher carbon yields than monomers upon carbonization). Characteristically, the ignition of aniline by fuming nitric acid results in a minor carbon residue (<1% after thorough washings) for practical consideration in this context [ 6 ].…”

Rapid Carbon Formation from Spontaneous Reaction of Ferrocene and Liquid Bromine at Ambient Conditions

“…An old yet classic example refers to the exothermic carbonization of sugar by concentrated sulfuric acid. Most recently, hypergolic reactions were successfully utilized from our group for the spontaneous and fast preparation of a variety of functional carbon materials, such as carbon nanosheets, crystalline graphite, graphitic carbon nitride, photoluminescent carbon dots, and fullerols, at ambient conditions [2][3][4][5]. By definition, in hypergolic reactions two reagents react immediately and energetically upon contact.…”