Hydrothermal N-doping assisted synthesis of poplar sawdust-derived porous carbons for carbon capture

Abstract

To optimize the CO₂ adsorption performance of carbon materials, this study proposed a preparation method for biomass-based porous carbon through hydrothermal carbonization coupled with nitrogen source optimization and K₂CO₃ activation. The effects of different nitrogen sources (urea, piperazine, melamine, and polyaniline) and activation temperatures on the physicochemical features and CO₂ adsorption characteristics of the porous carbons were systematically investigated. The results indicated that different nitrogen sources showed varying impacts on the CO₂ uptake of porous carbons, and not all nitrogen sources enhanced the adsorption performance. The urea and piperazine doped porous carbons exhibited relatively low nitrogen contents and specific surface areas. Whereas the melamine doped carbons showed higher nitrogen contents and specific surface areas, but lacked narrow micropores, limiting their CO₂ adsorption performance. In contrast, PAC-700, prepared using polyaniline as nitrogen source, featured a well-developed pore structure, abundant narrow micropores and pyrrolic-N groups, endowing it with enhanced CO₂ adsorption capability. At 0 °C/1 bar and 25 °C/1 bar, the CO₂ uptake of PAC-700 reached 6.85 and 4.64 mmol/g, respectively. Additionally, PAC-700 maintained a CO₂ uptake retention ratio of 99% after 5 adsorption-desorption cycles and exhibited good CO₂/N₂ selectivity of 22.4−51.6. These findings highlighted the advantageous CO₂ adsorption performance of PAC-700, indicating its substantial application potential in the domain of carbon capture.