Adsorption on Edge-Functionalized Bilayer Graphene Nanoribbons: Assessing the Role of Functional Groups in Methane Uptake

Abstract

A combination of ab initio and classical Monte Carlo simulations is used to investigate the effects of functional groups on methane binding. Using Møller–Plesset (MP2) calculations, we obtain the binding energies for benzene functionalized with NH2, OH, CH3, COOH, and H2PO3 and identify the methane binding sites. In all cases, the preferred binding sites are located above the benzene plane in the vicinity of the benzene carbon atom attached to the functional group. Functional groups enhance methane binding relative to benzene (−6.39 kJ/mol), with the largest enhancement observed for H2PO3 (−8.37 kJ/mol) followed by COOH and CH3 (−7.77 kJ/mol). Adsorption isotherms are obtained for edge-functionalized bilayer graphene nanoribbons using grand canonical Monte Carlo simulations with a five-site methane model. Adsorbed excess and heats of adsorption for pressures up to 40 bar and 298 K are obtained with functional group concentrations ranging from 3.125 to 6.25 mol % for graphene edges functionalized with OH, NH2, and COOH. The functional groups are found to act as preferred adsorption sites, and in the case of COOH the local methane density in the vicinity of the functional group is found to exceed that of bare graphene. The largest enhancement of 44.5% in the methane excess adsorbed is observed for COOH-functionalized nanoribbons when compared to H terminated ribbons. The corresponding enhancements for OH- and NH2-functionalized ribbons are 10.5% and 3.7%, respectively. The excess adsorption across functional groups reflects the trends observed in the binding energies from MP2 calculations. Our study reveals that specific site functionalization can have a significant effect on the local adsorption characteristics and can be used as a design strategy to tailor materials with enhanced methane storage capacity.

Methane adsorption on the surface of a model of shale: A density functional theory study

“…The interaction energies with BSSE corrections for all geometries were listed in Table 1. As shown in Figure 1, for all optimized configurations except for the kerogen_mI, methane is adsorbed directly above the carbon atoms of the kerogen rather than above the center of the six-membered ring 48 .…”

“…Sudeep N. Punnathanam and coworkers [48] have found that edge-functionalized graphene promoted the adsorption of methane. And methane was adsorbed on the sites above the center of the six-membered rings.…”

Edge functionalised & Li-intercalated 555-777 defective bilayer graphene for the adsorption of CO2 and H2O

“…The adsorption energy values of CO2 and H2O on the pristine graphene sheet are taken into account from our previous work 48 , in which a graphene cluster of size 4*4 was considered. The dimensions along with edge effects in graphene sheets have significant influence [37,59,60] on adsorption energy of molecular systems due to the density difference and the local deformation in the edge region than in the large sheet [37,59,60]. Particulary small sheets show pronounced changes in their chemical properties than large sheets due to functionalisation.…”

“…On the other hand, hydrogenated and hydroxylated pore structure have been utilized to increase the water flux through nanoporous graphene [12], suggesting hydrophilicity. Monte Carlo studies on edge-functionalised bilayer graphene nanoribbons reveal that the specific site functionalisation can have an impact on the local adsorption characteristics, which can be used for enhanced methane storage capacity [37]. Such results emphasise the significant effect of the edge-terminating group in graphene on its adsorption properties, and also an appropriate choice of edge group which helps for the permeation of gas molecules and promotes selectivity.…”

Molecular simulation of perfluorohexane adsorption in BAM-P109 activated carbon

“…This approach has been applied to investigate adsorption of different light gases in activated carbons, including CO 2 , N 2 , CH 4 and H 2 O, as well as binary and ternary mixtures (Cracknell et al., 1996; Heuchel et al., 1999; Jagiello and Schwarz, 1993; Kaneko et al., 1994; Lithoxoos et al., 2012; McCallum et al., 1998; Samios et al., 1997; Silvestre-Albero et al., 2012; Sweatman and Quirke, 2001). Many variants of the slit pore model have been developed over the years to incorporate various sources of heterogeneity in the structure, including walls of finite size and pores of finite length, surface groups, defects and so on (Brennan et al., 2002; Coasne et al., 2006; Do and Do, 2006; Gotzias et al., 2012; Jagiello and Olivier, 2009; Jorge et al., 2002; Jorge and Seaton, 2003; Kandagal et al., 2012; Liu and Wilcox, 2012; Lucena et al., 2010; McCallum et al., 1998; Müller et al., 1996; Vishnyakov et al., 1998; Wongkoblap and Do, 2006, 2007). The principal challenge in application of this approach is the reliability and realism of the PSD.…”