Perforated polygonal cobalt oxide (
) is synthesized using electrospinning and a hydrothermal method followed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravimetric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal
, we prepare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template- 10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sample A exhibits the perforated polygonal
with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF template. However, sample B and sample C synthesized perforated round
powders, respectively, due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonal
. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the successful formation of perforated polygonal
. Thus, perforated polygonal
can be applied to electrode materials of energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.