Sustainable biochar synthesis via synergistic H2O2-KOH modification for enhanced CO2 physisorption

Excessive CO₂ emissions lead to a gradual increase in global average temperatures and an increased frequency of extreme weather events. Exploiting advanced materials for CO₂ capture has become a key issue of concern to all countries. In this study, a new biomass carbonization strategy, co-modification by H₂O₂ and KOH, is proposed to prepare microporous biochar from pine sawdust with high CO₂ adsorption capacity. Results indicate that the co-modification strategy can produce biochar with a specific surface area as high as 3522.7 m²/g (with a micropore ratio of 90.3 %), which increases by 56.7 % compared to the biochar produced by biomass carbonization without H₂O₂ treatment. The adsorption properties of the co-modification-derived biochar are investigated by CO₂-TPD and TG, and the biochar exhibits a maximum CO₂ adsorption capacity of 6.60 mmol/g at 30 °C and retains over 91.2 % of this capacity after 10 cycles. It is revealed that H₂O₂-KOH modification can significantly promote the physisorption capacity of the biochar, highlighting the enhanced CO₂ capture efficiency due to alkaline hydrogen peroxide treatment on the biochar and its enhancement in CO₂ capture.