Engineering Nitrogen-Enriched Porous Carbons from Rice Husk via Mechanochemical–Thermal Processing for Enhanced CO2 Capture

Transforming agricultural residues into high-value carbon-based materials offers a promising route for sustainable carbon management. Here, we combine mechanochemistry and thermal treatment to convert carbonized rice husk mixed with urea into nitrogen-enriched biochar. The resulting material was benchmarked against a commercial carbon black, doped with nitrogen under identical conditions, enabling comparison of structural characteristics and gas adsorption performance. The integrated treatment significantly enhances CO2 uptake in the rice-husk-derived carbon, reaching 7.95 mmol/g (35 wt %) at 30 bar and T = 25 °C compared to 6.16 mmol/g (27 wt %) for the desilicated precursor. A smaller improvement is observed for CH4 adsorption (5.4 wt % compared to 4.8 wt % for the desilicated precursor) in the same conditions, while preliminary H2 tests at 1 bar and T = −196 °C show similar uptakes for both materials (4.6 mmol g–1). Overall, these results demonstrate that the combined mechanochemical–thermal approach provides an effective and scalable strategy to produce nitrogen-rich carbon adsorbents from biomass waste, with enhanced performance for CO2 capture applications.