Template-free synthesis of monolithic carbon xerogels with hierarchical porosity from resorcinol and formaldehyde via hydrothermal reaction.

ABSTRACT: Monolithic carbon xerogels with hierarchical porosity were prepared from resorcinol (R) and formaldehyde (F) via a base-catalysed hydrothermal polycondensation reaction, without a template and supercritical drying. First, an aqueous solution of resorcinol, formaldehyde and sodium carbonate was prepared by varying R/W (25-45) and R/C (1-10k) ratios to produce monolithic RF gels. The reaction was carried out in a pressurized Teflon mould at 100 °C for 6 h to give a co-continuous pore structure via spinodal decomposition and a tenacious gel to avoid supercritical drying. Next, the RF gels were dried for 42 h at 60 °C and another 6 h at 100 °C to produce RF xerogels without cracks, followed by pyrolysis in a tube furnace at 900 °C for 2 h under N₂ flow, and then activation at 1000 °C for 2, 4 or 6 h under CO₂ flow. Finally, the carbon xerogels were characterized by SEM and N₂ adsorption-desorption measurements. Monolithic RF gels were obtained from all combinations of R/W and R/C, but the gels from R/W = 45 exhibited a co-continuous large-pore structure, providing a specific surface area (SSA) of ∼650 m² g^-1, which increased to 3311 m² g^-1 (for R/C = 10k) at 6 h of CO₂ activation without exhibiting cracks. N₂ isotherms demonstrated that micro- and meso-pores were introduced via activation, forming hierarchical porosity in combination with large pores from spinodal decomposition without using a template.

SUBMITTER: Cho G 

PROVIDER: S-EPMC9080866 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature