Relevance of the Nuclear Quantum Effects on the Proton/Deuteron Transmission through Hexagonal Boron Nitride and Graphene Monolayers

Niranji Thilini Ekanayake, Jingsong Huang, Jacek Jakowski, Bobby G. Sumpter, Sophya Garashchuk

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

According to recent experiments, atomically thin hexagonal boron nitride and graphene are permeable to protons and deuterons (and not to other atomic species), and the experimental estimates of the activation energy are lower than the theoretical values by about 0.5 eV for the isolated proton-membrane transfer model. Our analysis of the electronic potential energy surfaces along the normal to the transmission direction, obtained using correlated electronic structure methods, suggests that the aqueous environment is essential to stabilize the proton transmission, as opposed to the hydrogen atom. Therefore, the process is examined within a molecular model of H2O-H(D)+-material-H2O. Exact quantum-mechanical scattering calculations are performed to assess the relevance of the nuclear quantum effects, such as tunneling factors and the kinetic isotope effect (KIE). Deuteration is found to affect the thermal reaction rate constants (KIE of 3-4 for hexagonal boron nitride and 20-30 for the graphene) and to effectively lower the barriers to the proton transfer by 0.2 and 0.4 eV for the two membranes, respectively. This lowering effect is reduced for the deuteron by approximately a factor of 3. A more comprehensive description of the proton transmission is likely to require an extended explicit aqueous environment.

Original languageEnglish
Pages (from-to)24335-24344
Number of pages10
JournalJournal of Physical Chemistry C
Volume121
Issue number43
DOIs
StatePublished - Nov 2 2017

Funding

This material is based upon work supported by the National Science Foundation under Grant No. CHE-1056188 and CHE-1565985 and by an ASPIRE grant from the Office of the Vice President for Research at the University of South Carolina. Part of the work was conducted at the Center for Nanophase Materials Sciences, a U.S. Department of Energy Office of Science User Facility. The research used an XSEDE allocation TG-DMR110037, resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and the USC HPC cluster, funded by the National Science Foundation under Grant No. CHE-1048629. We thank Professor Vitaly Rassolov for many helpful discussions. S.G. acknowledges Nanomaterials Theory Institute of the Center for Nanophase Materials Sciences at ORNL for hosting her as a short-term visitor, while on sabbatical leave from the University of South Carolina.

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