Superior CO2, CH4, and H2 uptakes over ultrahigh-surface-area carbon spheres prepared from sustainable biomass-derived char by CO2 activation

Porous carbon spheres (PCSs) with high uptakes for CO2, CH4, and H2 were prepared from sustainable starch-derived hydrochar via a simple CO2 activation without any template. The PCSs show regularly-spherical morphology, large surface area (3350 m2/g), and high pore volume (1.75 ml/g), which have been rarely reported for physically-activated carbons. Owing to the textural properties, their uptakes at 20 bar for CO2 (21.2 mmol/g, 298 K), CH4 (10.7 mmol/g, 298 K), and H2 (6.4 wt%, 77 K) all rank among the highest values ever reported for activated carbons, and the CH4 uptake is the highest one for activated carbons. Additionally, the adsorption and desorption of the aforementioned gases onto the material are reversible, indicating that the PCSs can be regenerated readily by pressure swing adsorption. Given the sustainability and environmental friendliness of the starch-derived feedstock, low costs of physical activation, large uptakes for multiple gases, and excellent adsorption reversibility, the obtained PCSs are promising candidates for storage of multiple energy-source-related gases.