Biomorphic activated porous carbons with complex microstructures from lignocellulosic residues

Transformation of coir fibers, coir pith and coconut shell endocarp microstructures is described for the formation of activated carbons. The carbonization/activation process was carried out using ZnCl2 as activating agent at 800 °C under CO2 atmosphere. The carbonization/activation process was evaluated by TGA/DTG measurements which evidenced an increase in the initial decomposition temperature along with increase in the carbon amount as an effect from ZnCl2. A detailed morphological analysis based on scanning electron microscopy with EDX analysis allowed the first description of the anisotropic cellular microstructure of these plant tissues and also evidenced the morphology transformation in all samples. From X-ray microtomography (micro-CT) images a random distribution of large channels was revealed for zinc containing samples (fibers and endocarp), as a result of contrast improvement in comparison to unmodified samples. Raman spectra of carbon samples were measured as a complementary microstructural evaluation on the basis of spectral deconvolution techniques, indicating that the size of graphitic crystallites as well as the size of clusters of imperfect graphene layers depends on the type of carbon precursor.