Porous texture evolution in activated carbon fibers prepared from poly (p-phenylene benzobisoxazole) by carbon dioxide activation

Activated carbon fibers (ACFs) were prepared from poly (p-phenylene benzobisoxazole) (PBO) in two varieties, as spun (AS) and high-modulus (HM). The precursor polymer was carbonized at 1123 K followed by physical activation with carbon dioxide at 1073 K to different burn-off (BO) degrees. The porous texture of the obtained materials was characterized by physical adsorption of nitrogen at 77 K and carbon dioxide at 273 K. Following CO₂ activation, the surface area and pore volume of the obtained ACFs progressively increased with increasing BO. The obtained adsorbents were principally supermicroporous, with a certain contribution from narrow mesopores. The pore size distributions became increasingly heterogeneous as the activation degree increased. The most significant difference between the two varieties of PBO used as precursors was a greater abundance of wide mesopores in the adsorbents prepared from the high-modulus variety.