Preparation of carbon spheres from potato starch and its stabilization mechanism

Carbon spheres perfectly retaining the original morphology of potato starch were prepared by a two-step process including stabilization and carbonization. The potato starch was first stabilized at 210 °C under air, and the stabilized samples were then carbonized at 600 °C for 1h under N2 atmosphere. In the process, stabilization treatment was the main step. The mechanism of stabilization was investigated by thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and differential scanning calorimetry, and the morphology of the carbon spheres was characterized by scanning electron microscopy (SEM). Results show that during stabilization, the loss of water and the occurrence of decomposition and condensation reactions result in the destruction of the crystallite structure in the original potato starch. Thus, during the carbonization step, further intermolecular cross-linking makes microcrystalline melting very difficult. This promotes the formation of monodispersed carbon spheres. The SEM results show that only if the potato starch undergoes adequate stabilization treatment (e.g., 12 h) before carbonization, can the carbon spheres perfectly retain the original shape of the potato starch.