Synergistic effects of heteroatom doping and narrow micropores on carbon dioxide capture in bamboo shoot shell-based porous carbon

Abstract

Owing to the exponential increase in human populace and anthropogenic activities, there has been a significant release of CO2 into the atmosphere, precipitating environmental quandaries such as the greenhouse effect. Consequently, the sequestration of CO2 emerges as an imperative endeavor. While prior research has illuminated the potential of surface-modified biochar to augment its sequestration efficacy via avenues such as activation and nitrogen doping, scant attention has been devoted to diatomic modification strategies. In this investigation, a novel array of nitrogen and sulfur co-doped porous carbons were engineered, utilizing discarded bamboo shoot husks as a carbonaceous substrate, thiourea as a dual-source dopant for nitrogen and sulfur, and potassium carbonate as an activating agent, through an intricate triphasic synthesis procedure. The study meticulously evaluated their CO2 sequestration capabilities, scrutinizing the influence of activator concentration and thermal activation conditions on the adsorption dynamics. The resultant N, S co-doped activated carbons manifested superlative CO2 capture capacities. A salient specimen, designated BSNC-800–2, showcased an unparalleled CO2 adsorptive uptake of 5.93 mmol/g at 0 °C and 3.83 mmol/g at 25 °C, attributable to its expansive specific surface area and substantive microporous volume. It was discerned that the interplay between the dopant concentrations and the proportion of narrow micropores was pivotal in modulating CO2 adsorption efficacy. Furthermore, these samples exhibited a suite of remarkable CO2 adsorption attributes, encompassing robust cyclic stability, elevated CO2/N2 selectivity, and a moderate heat of adsorption. Isothermal adsorption model simulations at 25 °C across all samples demonstrated a high fidelity to empirical observations when aligned with the Freundlich isotherm. Thermodynamic assessments posited that the sequestration of CO2 via the nitrogen-sulfur co-doped bamboo-derived porous carbons proceeded as a spontaneous and exothermic process, thereby corroborating the adsorbents' proficiency in CO2 entrapment. This study is anticipated to inspire new methods for synthesizing nitrogen-sulfur co-doped carbon and provide fresh insights into CO2 adsorption from flue gas using hetero-doped carbon.