Filamentous carbon materials obtained by catalytic decomposition of methane-rich hydrocarbons are used as advanced carbon material precursors, which in turn can be used in energy conversion processes and as catalyst support.
Functionalized carbon nanofilaments: the surface modification of carbon nanofilaments is critical for its subsequent use in different applications. Carbon nanofilaments are subjected to different combinations of functionalization treatment in acid and heat treatments, selectively modifying both the concentration and the nature of the surface oxygen groups. In addition, various treatments are performed under hydrothermal conditions to dope these carbon nanostructures with heteroatoms such as S or N. These materials have been used as catalysts or catalyst supports in reactions related to energy resources conversion (oil, biomass).
Graphite nanofibers: Synthetic graphite is a valuable material with a wide range of applications, from electrodes for aluminum and steel industries to fuel cell component and lithium ion batteries. The FCC has been involved in the research related to the use of carbon nanofilaments as precursors of synthetic graphite through a process known as graphitization, in collaboration with the Instituto Nacional del Carbón (INCAR-CSIC). The graphitization of filamentous carbon structures is carried out by subjecting the material to high temperature treatments (2400-2800ºC) under inert atmosphere, resulting in graphite nanofibers with similar crystalline parameters as commercial synthetic graphites produced from petroleum coke. Graphite nanofibers were characterized electrochemically as anodes in Li ion batteries, showing better performance than those obtained with commercial graphites. The materials developed in the context of this research have been the subject of an international patent.
Graphene-based materials: carbon nanofilaments are used as precursors of graphene based materials. This transformation is based on chemical oxidation of the carbon filaments using a modified Hummers method and subsequent exfoliation with ultrasounds. As a result of the oxidation/cleavage of different types of nanofilamentous carbon (nanofibers and carbon nanotubes) and carbon filaments showing different outside diameter distributions, graphene oxide-based materials with different chemical and morphological characteristics have been obtained and characterized: few layers graphene oxide sheets from exfoliation of both types of carbon nanofilaments, and quantum dots graphene oxide from carbon nanofibers. The effect of oxidation ratio used during the oxidation of carbon nanofilaments has been studied, as well as the subsequent reduction of these graphene materials using hydrothermal condition with superheated or supercritical water.
Garcia AB, Cameán I, Suelves I, Pinilla JL, Lázaro MJ, Palacios JM, et al. The graphitization of carbon nanofibers produced by the catalytic decomposition of natural gas. Carbon. 2009;47:2563-70.
Cameán I, García AB, Suelves I, Pinilla JL, Lázaro MJ, Moliner R. Graphitized carbon nanofibers for use as anodes in lithium-ion batteries: Importance of textural and structural properties. J Power Sources. 2012;198:303-7.
Torres D, Pinilla JL, Moliner R, Suelves I. On the oxidation degree of few-layer graphene oxide sheets obtained from chemically oxidized multiwall carbon nanotubes. Carbon. 2015;81:405-17.
Torres D, Pinilla JL, Galvez EM, Suelves I. Graphene quantum dots from fishbone carbon nanofibers. RSC Advances. 2016;6:48504-14.