Structure of carbon nanoparticles synthesized by adiabatic compression of acetylene and their application in supercapacitors

The work reports the study of the structure of carbon nanoparticles prepared by the pyrolysis of heliumdiluted acetylene under adiabatic compression in a piston reactor. At a pushing gas pressure of 0.5 MPa, 0.7 MPa, and 0.9 MPa the reaction gas was heated to temperatures of 400 °C, 600 °C, and 750 °C. By transmission electron microscopy it is found that carbon nanoparticles have a spherical shape and their size varies from 20 nm to 60 nm. The structural features of carbon nanoparticles are determined from the X-ray photoelectron spectroscopy data and the analysis of the near-edge X-ray absorption fine structure spectroscopy. Carbon nanoparticles prepared at a pushing gas pressure of 0.5 MPa have an amorphous structure and consist of hydrogenated carbon with impurities of polycyclic aromatic fragments. At a stronger compression ratio, carbon nanoparticles with a layered structure consisting mainly of sp2 hybridized carbon atoms are formed. The capacitance behavior and electrochemical impedance of carbon nanoparticle-based supercapacitors are compared.