Title: Surface Termination Dependent Work Function and Electronic Properties of Ti₃C₂T_x MXene

Abstract

MXenes, an emerging family of 2D transition metal carbides and nitrides, have shown promise in various applications, such as energy storage, electromagnetic interference shielding, conductive thin films, photonics, and photothermal therapy. Their metallic nature, wide range of optical absorption, and tunable surface chemistry are the key to their success in those applications. The physical properties of MXenes are known to be strongly dependent on their surface terminations. In this study, we investigated the electronic properties of Ti₃C₂T_x for different surface terminations, as achieved by different annealing temperatures, with the help of photoelectron spectroscopy, inverse photoelectron spectroscopy, and density functional theory calculations. We find that fluorine occupies solely the face-centered cubic adsorption site, whereas oxygen initially occupies at least two different adsorption sites, followed by a rearrangement after fluorine desorption at high annealing temperatures. The measured electronic structure of Ti₃C₂T_x showed strong dispersion of more than 1 eV, which we conclude to stem from Ti–O bonds by comparing it to calculated band structures. We further measured the work function of Ti₃C₂T_x as a function of annealing temperature and found that it is in the range of 3.9–4.8 eV, depending on the surface composition. A comparison of the experimental work function tomore » detailed density functional theory calculations shows that the measured value is not simply an average of the work function values of uniformly terminated Ti₃C₂ surfaces but that the interplay between the different surface moieties and their local dipoles plays a crucial role.« less

Authors:

Schultz, Thorsten  ^[1];

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Frey, Nathan C.  ^[2];

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Hantanasirisakul, Kanit  ^[3];

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Park, Soohyung  ^[4];

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May, Steven J. ^[3]; Shenoy, Vivek B. ^[2]; Gogotsi, Yury  ^[3];

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Koch, Norbert  ^[1]

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+ Show Author Affiliations

1. Humboldt Univ. of Berlin (Germany); Helmholtz-Zentrum Berlin (HZB), (Germany). German Research Centre for Materials and Energy
2. Univ. of Pennsylvania, Philadelphia, PA (United States)
3. Drexel Univ., Philadelphia, PA (United States)
4. Institut für Physik &, IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany; Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 02792, Korea

Publication Date:

2019-04-04

Research Org.:

Drexel Univ., Philadelphia, PA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1508005

Grant/Contract Number:  

SC0018618

Resource Type:

Accepted Manuscript

Journal Name:

Chemistry of Materials

Additional Journal Information:

Journal Volume: 31; Journal Issue: 17; Journal ID: ISSN 0897-4756

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE