Role of ferrocene-derived iron species in the catalytic graphitization of novolak resins

Abstract

Catalytic graphitization has been used since years, normally by heating from room temperature to 2227 or 3027 °C. Ferrocene was used to induce the graphitization in modified novolak phenolic resins synthesized in laboratory (PR). In this study, the intermediate carbon structures containing iron during the graphitization process, obtained after the different steps of heat treatment from 200 to 1000 °C, were identified concerning the oxidation states of iron and morphological and structural variations. The role of iron in these intermediate structures has not been fully evaluated yet by resonance and spectroscopy techniques; therefore, in this study, it will be discussed briefly. The following techniques were employed: X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), standard solid-state 13carbon nuclear magnetic resonance (solid-state 13C-NMR), 57Fe-Mossbauer and electron paramagnetic resonance (EPR) spectroscopies. In the material (PRFc) obtained by heat treatment for 5 h at 1000 °C, there were identified Fe2O3 nanocrystals, as well as Fe2O3, Fe3C and γ-iron present inside and outside of an onion-like hollow carbon structure. This structure of PRFc treated at 1000 °C has shown high efficiency in removing the pesticide atrazine (ATZ) in an aqueous medium and influenced the degradation mechanism of ATZ and the formation of atrazine-2-hydroxy (HAT).