Fabrication of one-dimensional PAN/g-C3N4 hollow nanofibers and improvement of photocatalytic properties

To solve global warming and depletion of fossil fuels problem, efforts have been made worldwide to use solar energy. Based on this background, artificial photosynthesis mimics the natural photosynthesis mechanism. Recently,... [ view full abstract ]

To solve global warming and depletion of fossil fuels problem, efforts have been made worldwide to use solar energy. Based on this background, artificial photosynthesis mimics the natural photosynthesis mechanism. Recently, graphitic carbon nitride (g-C₃N₄), which is a non-metallic visible-light organic semiconductor, has been studied. g-C₃N₄ has good thermal and chemical stabilities and has a narrow bandgap energy of 2.6 eV. Urea, thiourea, melamine have been widely used as precursors for g-C₃N_4.  These materials are inexpensive and can be readily used to synthesize g-C₃N₄. However, g-C₃N₄ has a high recombination rate, which lowers its photoelectrical activity. Copolymerization, doping, and the formation of composites and heterojunctions have been studied to overcome this issue. In our case, we coated one-dimensional (1D) g-C₃N₄ fibers on polyacrylonitrile (PAN) nanofibers using electrospinning method to fabricate a 1D heterostructure. This structure has numerous advantages including a high aspect and volume ratio, fast electron transfer rate, and provides effective separation of electron–hole pairs to reduce recombination.

PAN nanofibers with one-dimensional structure, were fabricated by electrospinning method so that the movement of electrons could be facilitated. In order to form hollow structure, it was carried in urea solution, and dried in the oven until the solution evaporated and obtained in powder form. After that, sintering was carried out in Ar atmosphere. Finally, one-dimensional hollow carbon nanofibers were obtained. After that, the precursor of g-C₃N₄ under the same process was used to uniformly coat the prepared hollow carbon nanofibers. For structural analysis, we observed hollow PAN/ g-C₃N₄ nanofibers using SEM and TEM. FT-IR analysis and XPS analysis were performed for the physical property analysis, and specific peaks corresponding to g-C₃N₄ were confirmed. In addition, the BET analysis was performed to confirm the specific surface area. As a result, it was confirmed that the one-dimensional hollow carbon nanofibers had an increased surface area  about 3 times higher than that of the existing PAN nanofibers. In addition, PEC, EIS, and H₂ production tests were performed to determine the electrochemical properties. Based on these analysis, it is expected to be applicable to solar cells, photocatalysts, hydrogen fuel cells, and lithium ion batteries.