Single-step dry synthesis of biomass-derived porous carbon for sustainable CO2 capture: experimental and simulation study

The utilization of bio-based affordable adsorbents is crucial for developing sustainable solutions for CO2 capture. In this work, an in-situ nitrogen-doped low-temperature CO2 adsorbent is synthesized via single-step dry pyrolysis of biomass (cow dung) and melamine mixtures (1:0, 1:1, 1:2) using KHCO3 as a green activating agent. The developed nitrogen-doped activated porous carbon (NDPC) is investigated using FE-SEM, XRD, BET, XPS and Raman spectroscopy. The optimized sample (NDPC-1) produced at a 1:1 ratio of cow dung to melamine, exhibits a nitrogen content of 2.95% and a high surface area (1153 m�/g) with the finely tuned micro- and mesoporous structure. These features result in an excellent CO2 adsorption capacity of 3.7 mol/kg at 1.013 bar and 303 K over 10 cycles. It shows 28% higher sorption capacity than pristine carbon without N-doping (CDAC) and 58% higher than pyrolyzed CD (CDC). The adsorption kinetics is studied using various adsorption models, and the Avrami model best fits the adsorption isotherm with a rate constant of 0.125 min-1. Furthermore, atomistic simulations (ReaxFF-MD) of CDAC and NDPC-1 frameworks were performed, using a force field parameterized for C/H/O/N chemistry. The simulation isotherms for CO2 adsorption computed using grand-canonical Monte Carlo (GCMC) show strong agreement with experimental data. Overall, the cow dung-derived N-doped porous activated carbon shows significant CO2 capture capacity over multiple cycles at 303 K. Results highlights its potential to be used as scalable materials for CO2 capture at low temperature.