A comparative study of porous and hollow carbon nanofibrous structures from electrospinning for supercapacitor electrode material development

Co-axial electrospinning is an efficient technique to develop core-shell or hollow nanofibrous structures. In this study electrospun carbon nanofibers with three different morphologies, i.e. solid nanofibers with porous structure (P-ECNF), hollow nanofibers with solid wall (H-ECNF), and hollow nanofibers with porous wall (HP-ECNF) were developed through bicomponent electrospinning and co-axial electrospinning of polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) by varying proportion of the sacrificial PMMA. Through comparative electrochemical analyses, it is revealed that the primary factors for electrochemical performance, i.e. specific capacitance, of the electrospun carbon nanofibrous materials are mesopore volume and total pore volume. The hollow structure as well as ordered carbon structure and intact fiber structure also benefits electrolyte transfer and subsequent electrochemical performance but is secondary. Overall the porous carbon nanofibrous electrode material from electrospinning PAN/PMMA (50/50) solution (P-ECNF-50-50) outperformed those hollow and hollow-porous counterparts from co-axial electrospinning and demonstrated the largest specific capacitance due to the largest mesopore volume as well as the largest total pore volume. This electrode material also showed excellent cycling stability (without any loss of specific capacitance) after 3,000 cycles of charging and discharging. It even showed some increase of specific capacitance with cycling test due to its relatively large amount of micropores.