Nano-CaCO3 as template for preparation of disordered large mesoporous carbon with hierarchical porosities

Abstract

A series of large mesoporous carbons (LMC, 20–50 nm) with hierarchical porosities has been prepared using commercially available CaCO₃ nanoparticles as a template, formaldehyde (PF) resin as carbon precursor, and HCl solution for removing the template. During the carbonization process, the CaCO₃ template decomposes releasing CO₂ which serves as an activating agent to active the carbon materials producing micropores and mesopores as well as enlarging pore sizes. This effect can be named as the “CO₂ inner-activation effect”, which is proved by comparing the carbon yield, N₂ adsorption/desorption isotherms, pore-size distribution and textual parameters of carbon materials carbonized at two critical temperatures, namely, 900 °C (higher than the pyrolysis temperature of CaCO₃) and 650 °C (lower than the pyrolysis temperature of CaCO₃). Our results show that the LMC samples prepared at different ratios of CaCO₃ to PF have BET surface areas ranging from 503 to 1215 m² g⁻¹, and pore volumes ranging from 1.8 to 9.0 cm³ g⁻¹. This one-step carbonization method with a CO₂ inner-activation effect provides a novel route to prepare large mesoporous carbons and hierarchical porous carbon materials.