Synthesis and Optical Properties of Two Cobalt Oxides (CoO and Co3O4) Nanofibers Produced by Electrospinning Process

In the present study, cobalt(II) oxide (CoO), which is hard to synthesize because of the chemical activity of cobalt metal, and the popular cobalt(II, III) oxide (Co3O4) have been successfully produced in smooth and continuous nanofibrous form by using the electrospinning technique. An aqueous cobalt acetate tetrahydrate and poly(vinyl alcohol) mixture has been electrospun and vacuously dried at 80 °C. Pure, smooth and solid Co3O4 nanofibers were produced when the dried nanofiber mats were calcined in air atmosphere at 700 °C. Water gas has been prepared by a novel technique to produce pure CoO nanofibers from the original cobalt acetate/poly(vinyl alcohol) nanofiber mats. The nanofiber mats have been hydrothermally treated in the presence of carbon at 300 °C in an especially designed reactor. The invoked physiochemical analyses have affirmed formation of both oxides in nanofibrous shape. The optical properties of the obtained nanofibers have been studied. UV−visible absorbance spectra have indicated that the band gap energy differences for the Co3O4 and CoO nanofibers are 2.4 and 2.21 eV, respectively.