Graphene as a promising additive to hierarchically porous carbon monoliths for enhanced H2 and CO2 sorption

This study aimed to examine a synthesis of hierarchically porous carbon monoliths (HPCM) doped with graphene oxide (GO) for H-2 and CO2 sorption applications. The synthesis procedure combining the sol-gel process with soft-templating was tuned by adding different quantities of GO (0.5; 2 and 10 wt% of the total amount of polycondensation mixture), as well as different carbonization temperatures (500 degrees C, 900 degrees C) of the composite materials during which the reduction of GO to graphene occurs. The degree of GO reduction to graphene and its incorporation into the HPCM matrix of prepared materials were characterized by Raman, FTIR, SEM, TEM, and elemental analysis. Although incorporation was successful, the higher pyrolysis temperature of 900 degrees C promotes the reduction of GO to graphene, which enhances the (ultra)microporosity (proven by gas physisorption ex-periments) of the samples, especially of the one with 10% GO addition. The effectivity of materials towards H-2 and CO2 sorption was examined by sorption of H-2 (77 K, up 1 bar) and CO2 (273 K, up 1 bar), respectively. Addition of any amount of GO together with the used lower pyrolysis temperature of 500 degrees C reduced the adsorption capacity of the samples for CO2 (from 2.4 to 1.8 mmol g(-1)) and H-2 (from 5.8 to 3.6 mmol g(-1)) compared to the original HPCM. On the bright side, a 10% addition of GO in combination with a pyrolysis temperature of 900 degrees C results in industrially perspective material with an H-2 and CO2 adsorption capacity of 9.6 mmol g(-1) and 4.6 mmol g(-1), respectively.

Automated summary

This study investigated the synthesis of hierarchically porous carbon monoliths doped with graphene oxide for H-2 and CO2 sorption applications. By adjusting the synthesis procedure and carbonization temperature, the degree of reduction of graphene oxide and its incorporation into the matrix were characterized. The addition of 10% graphene oxide at a pyrolysis temperature of 900 degrees C resulted in a promising material with high adsorption capacities for H-2 and CO2.