Fabrication of monodisperse polyacrylonitrile hollow microspheres containing transition metals and low-temperature catalytic graphitization

In this study, a novel approach was presented for controllable preparation of polyacrylonitrile (PAN) hollow microspheres, and PAN-derived graphite carbon microspheres were synthesized through a simple and facile method, overcoming the intrinsic non-graphitizable property of PAN under low temperatures. The pure PAN microspheres and PAN/M (M = Fe, Co, Ni) microspheres were fabricated by the microfluidic technique and solvent evaporation method. Subsequently, the graphitization process was performed for carbon growth of all PAN microspheres at carbonization temperatures of 800 °C, 1000 °C,1200 °C, and 1400 °C, respectively. The effects of transition metals on the stability of compound droplets, monodispersity, and morphology of microspheres were investigated. The carbon resides was given by TG analysis, and the degree of graphite was characterized by the Raman spectra, XRD patterns, and TEM image. The results showed that the three transition metals exhibited different catalytic graphitization effects, leading to a different degree of catalytic graphitization. Understanding the catalytic graphitization effect of Fe, Co, and Ni on PAN microspheres offers new strategies for converting polymer-derived microspheres to invaluable synthetic graphite carbon, which has potential application in upcycling of waste plastics, catalysis, absorption, thermally conductive materials, and energy conversion.