One-pot preparation of functionalized nanostructured carbons

Functionalized nanostructured carbons were obtained by template method using sucrose as carbon precursor and silica gel SG60 as structure directing agent. To introduce acid groups into carbon a different amount of phosphoric acid was added to sucrose (impregnation ratio 0-1) before filling the pores of silica gel. After carbonization at 800 °C silica template was removed by dissolution in HF. Carbons were characterized by SEM/EDX, nitrogen adsorption at 77 K and acid-base titration. Pore size distributions (PSD) indicated that carbons obtained at impregnation (IR) of 0-0.75 have pores with size less than 4 nm due to crack during carbonization and activating action of phosphoric acid. Templated pores with 5.1 nm are observed in all carbons. PSD significantly changed at IR = 1 showing additional large mesopores of 8.2 nm. Acid-base titration revealed very high concentration of acid surface groups (4.1-4.7 mmol/g), significant amount of which (46 ± 3%) belongs to phosphate groups (pK = 2.3 ± 0.1). Another surface groups are weak carboxylic (pK = 5.9 ± 0.3), lactone and/or enol (pK = 7.2 ± 0.2, pK = 8.8 ± 0.3) and phenol groups (pK = 10.5 ± 0.3). SEM showed smooth carbon surface up to impregnation ratio 0.5 and increasing roughness at higher amount of phosphoric acid.