CO2 adsorption thermodynamics over N-substituted/grafted graphanes: a DFT study.
This work examines CO2 adsorption over various N-substituted/grafted graphanes to identify the promotional effects of various N-functionalities have on the adsorption characteristics using DFT. CO2 adsorbs weakly on a graphane surface functionalized with a single, isolated substituted N- or grafted NH2-sites. The presence of coadsorbed H2O on the surface promotes CO2 adsorption on both N- and NH2-sites, with highly exothermic adsorption energies (∼-50 kJ mol(-1)). Directly grafted -NH2 or -OH functional groups on C atoms adjacent to C atoms which have a -NH2 group grafted suffer from geometrical restrictions preventing dual stabilization of formed carbamate upon adsorption of CO2. CO2 adsorption can be greatly enhanced with the presence of a -OH group or second -NH2 group in the proximity of a -NH2 site on graphane, and only if a n(-CH2-) (n ≥ 1) linker is introduced between the -NH2 or -OH and graphane surface (adsorption energies of -58.8 or -43.1 kJ mol(-1) at n = 2). The adsorption mechanistics provided by DFT can be used to guide the atomic-level rational design of N-based graphane and carbon adsorbents for CO2 capture.
Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Education Ministry, and School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, China.
Jing
J
Xiao
Siddarth
S
Sitamraju
Michael J
MJ
Janik