title: Aqueous proton transfer across single-layer graphene.
abstract: Proton transfer across single-layer graphene proceeds with large computed energy barriers and is therefore thought to be unfavourable at room temperature unless nanoscale holes or dopants are introduced, or a potential bias is applied. Here we subject single-layer graphene supported on fused silica to cycles of high and low pH, and show that protons transfer reversibly from the aqueous phase through the graphene to the other side where they undergo acid-base chemistry with the silica hydroxyl groups. After ruling out diffusion through macroscopic pinholes, the protons are found to transfer through rare, naturally occurring atomic defects. Computer simulations reveal low energy barriers of 0.61-0.75 eV for aqueous proton transfer across hydroxyl-terminated atomic defects that participate in a Grotthuss-type relay, while pyrylium-like ether terminations shut down proton exchange. Unfavourable energy barriers to helium and hydrogen transfer indicate the process is selective for aqueous protons.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60201, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Achtyl
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Unocic
authors.affiliation: Departments of Chemical Engineering and Chemistry, University of Virginia, 102 Engineers' Way, Charlottesville, Virginia 22904-4741, USA.
authors.forename: Lijun
authors.initials: L
authors.lastname: Xu
authors.affiliation: Departments of Chemical Engineering and Chemistry, University of Virginia, 102 Engineers' Way, Charlottesville, Virginia 22904-4741, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Muralikrishna
authors.initials: M
authors.lastname: Raju
authors.affiliation: Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, Pennsylvania 16801, USA.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Measurement Science and Systems Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37931, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sacci
authors.affiliation: Measurement Science and Systems Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37931, USA.
authors.forename: Ivan V
authors.initials: IV
authors.lastname: Vlassiouk
authors.affiliation: 1] Department of Chemistry, University of Puerto Rico, Río Piedras Campus; San Juan, Puerto Rico 00931, USA [2] Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Pasquale F
authors.initials: PF
authors.lastname: Fulvio
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Panchapakesan
authors.initials: P
authors.lastname: Ganesh
authors.affiliation: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wesolowski
authors.affiliation: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Dai
authors.affiliation: Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, Pennsylvania 16801, USA.
authors.forename: Adri C T
authors.initials: AC
authors.lastname: van Duin
authors.affiliation: 1] Departments of Chemical Engineering and Chemistry, University of Virginia, 102 Engineers' Way, Charlottesville, Virginia 22904-4741, USA [2] Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Neurock
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60201, USA.
authors.forename: Franz M
authors.initials: FM
authors.lastname: Geiger