Tunable synthesis of C-SiOxCy monoliths

This study establishes key structure–property relationships, offering valuable guidelines for designing porous monolithic C-SiO_xC_y materials for energy storage sensors, and electrocatalysis. We report a tunable sol-gel synthesis of monolithic C-SiO_xC_y composites with tailored physicochemical and electrical properties. By combining resorcinol, formaldehyde, TEOS, APTES, and kapok fibers, twenty-one formulations were prepared while systematically varying five synthesis parameters: TEOS-to-resorcinol molar ratio, sol concentration, sol pH, drying method, and pyrolysis temperature. The resulting composites exhibited silica contents ranging from 19 to 80 wt%, bulk densities from 0.10 to 1.11 g/cm³, specific surface areas up to 562 m²/g, and electrical conductivities reaching 8 S/cm. Structural analyses (SEM, ²⁹Si NMR, N₂ adsorption) revealed that the materials consist of integrated hybrid networks rather than separate carbon and silica domains. Factor analyses highlighted the dominant roles of TEOS/R on composition and porosity, supercritical drying on texture, and pyrolysis temperature on conductivity. Acidic conditions and sol dilution promoted high surface areas and pore volumes, while alkaline pH and carbon-rich environments enhanced electrical transport.