Facile and environmentally friendly synthesis of ultramicroporous carbon spheres: A significant improvement in CVD method

A new and environmentally friendly non-caustic route to synthesize ultramicroporous carbon spheres (CS) via a simple one-step non-catalytic and activation-free chemical vapor deposition (CVD) method is described. The CVD method was applied at different temperatures, 600–900 °C; 800 °C was identified as the optimum for CS formation using a safe solid feedstock. The ultramicropores allow the effective interaction of the sorbent with CO2, resulting in high carbon capture capacity at both atmospheric and lower pressures. Specific surface area and total pore volume were influenced by the deposition temperature, leading to an appreciable change in overall carbon dioxide capture capacity. At atmospheric pressure, the highest CO2 adsorption capacities were ca. 4.0 mmol.g−1 and 2.9 mmol.g−1 at 0 °C and 25 °C, respectively, for the best CS. At lower pressure, 0.15 bar, the CO2 adsorption capacities were 2.0 mmol.g−1 and 1.1 mmol.g−1, again at 0 °C and 25 °C. The CS showed good sorption/desorption cyclability, ease of regeneration, favorable selectivity over N2 of 30:1 at 25 °C, and rapid kinetics. The proposed method is suitable for large-scale adoption since high pyrolysis temperatures are already used in multi-million-ton industries such as that of carbon black production. [Display omitted] •A green, rapid, and scalable method to prepare microporous carbon spheres was developed.•A safe and solid feedstock was used for CVD synthesis of carbon sphere.•The presented CVD method was template and catalyst-free.•Carbon spheres with high abundance of ultramicropores were obtained without any activating agents.•Self-activated carbon spheres were tested for CO2 capture and showed good capacity for low pressure CO2 capture.