Methanol Adsorption on Graphene

Table 1

Theory data for adsorption of methanol on graphene. Included is the adsorption energy 𝐸_𝑎, the distance of the methanol O atom from graphene, 𝑑_O, the adsorption configuration (C–O axis approximately parallel with the plane of graphene or C–O axis approximately perpendicular to the plane of graphene with the O atom pointing up or down), molecular coverage, and the orthogonal unit cell used in the calculations, given in units of 𝑎_𝑔=√3𝑎₀ with 𝑎₀=1.43 Å. All unit cells are 19 Å in the direction perpendicular to the plane of graphene. The coverages in our calculations are estimated from the approximate molecular area of methanol on graphene 17.6 Ų determined from X-ray diffraction studies in [24].

	Structure	Unit cell	Coverage	𝐸𝑎		𝑑O
			[ML]	[kJ/mol]	[meV]	[Å]
Theory, vdW-DF (our calculations)
Single molecule	Parallel	3√3×5	0.11	20.6	214	3.33
	Parallel	3√3×4	0.14	20.7	215	3.33
	Parallel	3√3×3	0.18	21.1	219	3.33
	O down	3√3×3	0.18	14.6	151	3.20
	O up	3√3×3	0.18	15.5	160	4.87
	Parallel	1√3×2	0.83	30.5	316	3.55
Three cluster	Parallel	3√3×3	0.55	30.4	315	3.31–3.54
Five cluster	Parallel	3√3×3	0.92	34.9	361	3.35–4.50
Theory, DFT-D and MP2-based (Pankewitz and Klopper)^a
Single molecule, DFT-D with BP86	Parallel	Benzene		14.8		3.35
Single molecule, DFT-D with BP86	Parallel	Coronene		18.7		3.32
Single molecule, DFT-D with BP86	Parallel	112-C PAH		20.0		3.32
Single molecule, DFT-D with BP86^b	O up	Coronene		~11		~4.8
Single molecule, SCS-MP2 with PB86	Parallel	Benzene		13.8		~3.4
Single molecule, SCS-MP2 with PB86	Parallel	Coronene		18.3		~3.3

aOrbital-based calculations with a TZVP basis, [7].
^bEnergy estimated from Figure  8 of [7].