Synergistic Effect of Nitrogen Doping and Ultra-Microporosity on the Performance of Biomass and Microalgae-Derived Activated Carbons for CO₂ Capture

Abstract

We report a unique naturally derived activated carbon with optimally incorporated nitrogen functional groups and ultra-microporous structure to enable high CO 2 adsorption capacity. The coprocessing of biomass (Citrus aurantium waste leaves) and microalgae (Spirulina) as the N-doping agent was investigated by probing the parameter space (biomass/microalgae weight ratio, reaction temperature, and reaction time) of hydrothermal carbonization and activation process (via the ZnCl 2 /CO 2 activation) to generate hydrochars and activated carbons, respectively, with tunable nitrogen content and pore sizes. The central composite-based design of the experiment was applied to optimize the parameters of the prehydrothermal carbonization procedure resulting in the fabrication of N-enriched carbonaceous products with the highest possible mass yield and nitrogen content. The resulting hydrochars and activated carbon samples were characterized using elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and Brunauer−Emmett−Teller surface area analysis. We observe that while N-doping and the activation process can individually enhance the CO 2 adsorption capacity to some extent, it is the combined effect of the two processes that synergistically work to greatly increase the adsorption capacity of the N-doped activated carbon by an amount which is more than the sum of individual contributions. We analyze the origins of this synergy with both physical and chemical characterization techniques. The resulting naturally derived activated carbon demonstrates one of the highest CO 2 adsorption capacities (8.43 mmol/g) with rapid adsorption kinetics and good selectivity and reusability.

Oxygen and nitrogen enriched pectin-derived micro-meso porous carbon for CO2 uptake

“…60,61 The initial consequence of nitrogen doping is that it promotes a larger density of N-doped basic active sites for enhanced van der Waals interactions between nitrogen functional groups and CO 2 molecules, which increases adsorption capacity. 62 CO 2 adsorption could be enhanced by the existence of a microporous structure and strong interactions between CO 2 molecules and the framework (particularly Ncontaining groups) via H-bonding or dipole-quadrupole interactions in N-enriched porous carbons. 63 The strong hydrogenbonding interactions between CO 2 molecules and hydrogen atoms (from CH and NH groups) on the carbon surface are greatly enhanced by the intercalation of N atoms into the carbon framework, which acts for the excellent CO 2 capture behavior of N-doped porous carbons.…”

Microwave-Assisted Sulfonation of Lignin for the Fabrication of a High-Performance Dye Dispersant

“…Elemental analysis of the sulfonated lignin samples was performed using PE 2400 II (PerkinElmer, USA) by the Pregl–Dumas method. For detailed parameters, refer to the literature …”

Green self-activating synthesis system for porous carbons: Celery biomass wastes as a typical case for CO2 uptake with kinetic, equilibrium and thermodynamic studies

“…The Qst, conversely, drops as the surface coverage rises. This is due to weaker interactions between restricted CO2 in larger pores and the surface [102].…”