Graphene-like materials supported on sepiolite clay synthesized at relatively low temperature

• Published in: Carbon (New York) 2024-01, Vol.218, p.118767, Article 118767
• Main Authors: Barra, Ana, Lazăr, Oana, Mihai, Geanina, Bratu, Cătălina, Ruiz-García, Cristina, Darder, Margarita, Aranda, Pilar, Enăchescu, Marius, Nunes, Cláudia, Ferreira, Paula, Ruiz-Hitzky, Eduardo
• Format: Article
• Language: English
• Subjects: Hydrothermal carbonization; Microwave pyrolysis; Sepiolite; Sucrose; Supported graphene
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2023.118767

The preparation of solids with graphitic structure usually requires synthesis procedures using very high temperatures. In this work, a comparative study involving different experimental strategies of synthesis at relatively low temperature was carried out to obtain graphene-like materials supported on microporous sepiolite (SEP) clay. The final objective was the optimization of the development of new clay-graphitic nanostructured materials to achieve porous solids while saving energy and time during the preparation stages. The pyrolysis of sucrose (SUC), used as carbon precursor, was accomplished by microwave (MW) pyrolysis or tube furnace (TF) pyrolysis at 200 or 500 °C followed by a hydrothermal carbonization (HTC) step. The resulting carbon-clay nanoarchitectures were characterized by Raman and Infrared spectroscopy, X-ray diffraction, elemental analysis, electron microscopy, and nitrogen adsorption-desorption isotherms. The MW200 and TF200 treatments caramelized SUC and the post-HTC step was fundamental to obtain porous carbonaceous materials. The TF500 pyrolysis produced predominantly crystalline carbon, while the MW500 pyrolysis formed an amorphous material. Moreover, the high-resolution transmission electron microscopy observations of TF500 sample revealed a crystalline material with a d-spacing of 0.33 nm, matching the graphitic lattice. All the treatment conditions performed at 500 °C i.e., MW or TF followed or not by HTC, resulted in mesoporous carbons with a specific surface area above 200 m2 g−1. The MW pyrolysis saved 100 min of the reaction time in comparison to TF pyrolysis to obtain the carbonaceous porous materials. [Display omitted] •Pyrolysis of sucrose/sepiolite at 500 °C produces graphene-like materials.•Tube furnace pyrolysis at 500 °C has the advantage of producing crystalline carbon.•Microwave pyrolysis at 500 °C saves 100 min, producing amorphous carbon.•Carbon-clay nanostructures synthesized at 500 °C presented a SBET > 200 m2 g−1.•Hydrothermal carbonization after pyrolysis at 200 °C improves graphitization and porosity.