The interaction of sulfuric acid with graphene and formation of adsorbed crystals

Abstract

Density functional theory has been used to analyse the interaction between sulfuric acid andgraphene. Four different coverages, ranging from a nearly isolated sulfuric acid molecule (oneH2SO4 molecule per 32 Catoms) to a bilayer (one H2SO4 molecule per 4 C atoms) have been studied calculating geometries, binding energies,charge transfers and band structures. The results show that there is protonationof the graphene sheet by the acid, in accordance with experimental results forH2SO4 adsorbed onto highly oriented pyrolytic graphite and for single-wall carbon nanotubes inconcentrated sulfuric acid. Nevertheless the electronic structure of graphene is not heavilyaffected and its zero-band-gap semiconducting behaviour is preserved. As the coverageincreases, the acid molecules rotate approaching their orientation in the purecrystal, showing that graphene can template the growth of a sulfuric acid crystal.