title: Atomic Structure and Dynamics of Single Platinum Atom Interactions with Monolayer MoS2.
abstract: We have studied atomic level interactions between single Pt atoms and the surface of monolayer MoS2using aberration-corrected annular dark field scanning transmission electron microscopy at an accelerating voltage of 60 kV. Strong contrast from single Pt atoms on the atomically resolved monolayer MoS2lattice enables their exact position to be determined with respect to the MoS2lattice, revealing stable binding sites. In regions of MoS2free from surface contamination, the Pt atoms are localized in S vacancy sites and exhibit dynamic hopping to nearby vacancy sites driven by the energy supplied by the electron beam. However, in areas of MoS2contaminated with carbon surface layers, the Pt atoms appear at various positions with respect to the underlying MoS2lattice, including on top of Mo and in off-axis positions. These variations are due to the Pt bonding with the surrounding amorphous carbon layer, which disrupts the intrinsic Pt-MoS2interactions, leading to more varied positions. Density functional theory (DFT) calculations reveal that Pt atoms on the surface of MoS2have a small barrier for migration and are stabilized when bound to either a single or double sulfur vacancies. DFT calculations have been used to understand how the catalytic activity of the MoS2basal plane for hydrogen evolution reaction is influenced by Pt dopants by variation of the hydrogen adsorption free energy. This strong dependence of catalytic effect on interfacial configurations is shown to be common for a series of dopants, which may provide a means to create and optimize reaction centers.
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Huashan
authors.identifier: 0000-0002-3439-3864
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, United Kingdom.
authors.forename: Shanshan
authors.identifier: 0000-0003-3750-6737
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, United Kingdom.|JEOL Ltd. , 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.|Electron Physical Sciences Imaging Center, Diamond Light Source Ltd , Didcot, Oxfordshire, OX11 0DE, United Kingdom.
authors.forename: Hidetake
authors.initials: H
authors.lastname: Sawada
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Grace G D
authors.initials: GG
authors.lastname: Han
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, United Kingdom.
authors.forename: Thomas
authors.initials: T
authors.lastname: Samuels
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, United Kingdom.|Electron Physical Sciences Imaging Center, Diamond Light Source Ltd , Didcot, Oxfordshire, OX11 0DE, United Kingdom.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Allen
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, United Kingdom.|Electron Physical Sciences Imaging Center, Diamond Light Source Ltd , Didcot, Oxfordshire, OX11 0DE, United Kingdom.
authors.forename: Angus I
authors.initials: AI
authors.lastname: Kirkland
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Grossman
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, United Kingdom.
authors.forename: Jamie H
authors.identifier: 0000-0002-1271-2019
authors.initials: JH
authors.lastname: Warner
keywords: 2D materials; ADF-STEM; MoS2; Pt dopants; catalysts; dopants