Green hydrogen and porous carbon materials co-harvested through CO₂-steam co-mediated gasification

A novel strategy was proposed for valorizing biomass to co-harvest green H₂ and functionalized porous carbon materials. Gasification of cotton stalk (CS) was first operated in varying gasifying agents. Both the gas yields and the surface area of gasification carbon materials obtained in the gasifying combinations were higher than their counterparts, indicating the synergistic effect between the mixed gasifying agents. In particular, the highest H₂ yield (15.3 mmol/g) and syngas purity (88.01 %) were found in the mixed CO₂-steam gasifying agents. The largest surface area (671 m²/g) and pore volume (0.338 cm³/g) were also achieved in the mixed gasifying agents of CO₂ and steam. Importantly, these carbon materials were effective for adsorbing toxic phenolic compounds in hydrothermal wastewater (removal efficiency > 52 %). Overall, this study provided a promising strategy to valorize agricultural biomass into green H₂ and functionalized porous carbon materials for toxic wastewater treatment.