4. Conclusions
Lignin fibers with and without platinum were synthesized by a straightforward experimental method in a single step by electrospinning of a lignin/ethanol/platinum acetylacetonate and lignin/ethanol solutions, respectively. The fibers obtained were stabilized by an air oxidation process in order to avoid fiber fusion during the subsequent carbonization step. The stabilization stage increases the oxygen content of the fibers. The stabilized fibers were carbonized at differ-ent temperatures between 600 and 1000 °C. The increase of the carbonization temperature decreased the oxygen content of the fibers, increasing the carbon and surface plati-num proportion, as well as result in fibers with a higher structural order. Carbon fibers with surface platinum of 0.6% in weight were obtained. All the carbon fibers obtained present an essentially microporous structure. The increase of carbonization temperature produces a development of the porous structure of the carbon fibers. Carbon fibers with and without platinum with apparent surface areas of 1178 and 1195 m2/g, respectively, and micropore volumes of 0.52 cm3/g were obtained. The thermal treatment of the lignin-based stabilized fibers produced a decrease of the final carbon fibers diameters. TEM micrographs show carbon fibers with no defects, very smooth surface and size in the range of 400 nm to 1 lm. The carbon fibers obtained present a high oxidation resistance, probably due to a certain degree of structural order and to the lack of surface defects. The presence of platinum slightly reduces the oxidation resis-tance of the lignin-based carbon fibers