缺陷工程已被證明是觸發二維材料惰性表面的有效方法，因為表面缺陷通常是活性位點。在我們的研究中，我們通過製造表面的碲缺陷（對應於未鍵結滿的 鉑(Ptuc)）增強了 PtTe2 表面的反應能力，並且可以通過控制氬離子 (Ar+) 轟擊的量來調控表面的缺陷密度。通過反射高能電子衍射 (RHEED)、光電子能譜 (PES) 和近常壓 X 射線光電子能譜 (APXPS)，我們證明氬離子轟擊主要產生表面碲缺陷，並且其數量幾乎與氬離子轟擊的劑量成高度正相關。
藉由光電子能譜我們看到了甲醇有缺陷的 PtTe2 表面上分解成CHxO 和 CHx這兩種產物，並且這些產物的產量Ptuc 的數量之間存在高度正相關，這意味著 對於甲醇分解來說Ptuc 是表面的活性位點。因此我們可以通過控制氬離子轟擊的時間來控制表面 Ptuc 的數量，並進一步影響 PtTe2 的表面反應能力。
使用基於同步輻射光源的近常壓 X 射線光電子能譜，我們發現了在接近常壓的環境中吸附的甲醇引發了PtTe2表面上碲缺陷的形成。由Te 4d 與 Pt 4f的光電子能譜強度的比例降低和未鍵結滿的鉑光電子訊號的增加我們進一步的證實表面碲缺陷的增加是由分解性吸附的甲醇所引起。隨著甲醇氣壓逐漸增加至0.01 mbar，進一步增強的甲醇分解反應（由原子碳和 CHx 的產生表明）和逐漸增加的碲缺陷數量意味著甲醇的分解和反應能力的增強是相輔相成的。增強的反應能力加速了甲醇的分解；而加速的甲醇分解議會促進反應能力的加強。
我們還注意到碲缺陷的數量在甲醇壓力 0.01 mbar 左右達到飽和。該結果意味著，除了傳統的缺陷工程策略（例如，退火、離子轟擊或等離子體處理）之外，我們提出了另一種在二維材料上製造表面缺陷的方法。

Defect engineering has been shown as an efficient way to activate inert basal planes of 2D materials, as surface defects are typically active sites. In this study, we show that the reactivity of PtTe2 basal plane is enhanced by introducing surface Te-vacancies, corresponding to under-coordinated surface Pt (Ptuc), and the defect density can be controlled with Argon ion (Ar+) bombardment. With reflection high energy electron diffraction (RHEED), photoelectron spectroscopy (PES), and ambient pressure X-ray photoelectron spectroscopy (APXPS), we demonstrate that the Ar+ bombardment produces primarily surface Te-vacancies and the number of Ptuc grows almost in linear proportion with the Ar+ bombardment time. These spectra also indicate the decomposition of methanol adsorbed on the defective PtTe2 surface, evidenced by the formation of CHxO and CHx, and a highly positive correlation between the numbers of decomposed methanol and Ptuc, implying Ptuc as an active site toward the methanol decomposition. The surface reactivity of PtTe2 can therefore be manipulated by controlling the number of Ptuc through the Ar+ bombardment. With synchrotron-based APXPS, we show that the surface Te-vacancies on PtTe2 were enhanced by adsorbed methanol. The increased surface Te-vacancies were indicated by the decreased ratio of the Te 4d to Pt 4f core-level signals and increased Pt 4f signals at smaller binding energy, reflecting increased undercoordinated Pt (Ptuc). With increasing methanol exposure from high vacuum to near-ambient pressure (up to 0.1 mbar), both methanol decomposition, indicated by the production of atomic carbons and CHx, and the number of Te-vacancies were significantly promoted, implying that these processes could promote each other. We also noted that the number of Te-vacancies was saturated at about methanol pressure 0.01 mbar. The result implies, in addition to traditional defect engineering strategies (e.g., annealing, ion bombardment or plasma treatment), an alternative approach to engineer surface defects on layered 2D materials.

[1] J. Hu et al., "Sulfur vacancy-rich MoS2 as a catalyst for the hydrogenation of CO2 to methanol," Nature Catalysis, vol. 4, no. 3, pp. 242-250, 2021/03/01 2021.
[2] J. Yang et al., "Single Atomic Vacancy Catalysis," ACS Nano, vol. 13, no. 9, pp. 9958-9964, 2019/09/24 2019.
[3] A. Politano et al., "Tailoring the Surface Chemical Reactivity of Transition-Metal Dichalcogenide PtTe2 Crystals," Advanced Functional Materials, vol. 28, no. 15, 2018.
[4] X. Wang et al., "Single-Atom Vacancy Defect to Trigger High-Efficiency Hydrogen Evolution of MoS2," Journal of the American Chemical Society, vol. 142, no. 9, pp. 4298-4308, 2020/03/04 2020.
[5] J. Xie et al., "Controllable Disorder Engineering in Oxygen-Incorporated MoS2 Ultrathin Nanosheets for Efficient Hydrogen Evolution," Journal of the American Chemical Society, vol. 135, no. 47, pp. 17881-17888, 2013/11/27 2013.
[6] J. Xu et al., "Frenkel-defected monolayer MoS2 catalysts for efficient hydrogen evolution," Nature Communications, vol. 13, no. 1, p. 2193, 2022/04/22 2022.
[7] Y. Chen et al., "Tuning Electronic Structure of Single Layer MoS2 through Defect and Interface Engineering," ACS Nano, vol. 12, no. 3, pp. 2569-2579, Mar 27 2018.
[8] H. Li et al., "Corrigendum: Activating and optimizing MoS2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies," Nat Mater, vol. 15, no. 3, p. 364, Mar 2016.
[9] P. E. Evans et al., "Methoxy Formation Induced Defects on MoS2," The Journal of Physical Chemistry C, vol. 122, no. 18, pp. 10042-10049, 2018.
[10] C.-H. Wang, S.-T. Chang, S.-Y. Chen, and Y.-W. Yang, "New ambient pressure X-ray photoelectron spectroscopy endstation at Taiwan light source," AIP Conference Proceedings, vol. 2054, no. 1, p. 040012, 2019.
[11] M. R. Alexander, G. E. Thompson, X. Zhou, G. Beamson, and N. Fairley, "Quantification of oxide film thickness at the surface of aluminium using XPS," Surface and Interface Analysis, vol. 34, no. 1, pp. 485-489, 2002.
[12] S. Nappini et al., "Transition-Metal Dichalcogenide NiTe2: An Ambient-Stable Material for Catalysis and Nanoelectronics," Advanced Functional Materials, vol. 30, no. 22, p. 2000915, 2020.
[13] L. Sciortino, U. Lo Cicero, E. Magnano, I. Píš, and M. Barbera, Surface investigation and aluminum oxide estimation on test filters for the ATHENA X-IFU and WFI detectors (SPIE Astronomical Telescopes + Instrumentation). SPIE, 2016.
[14] S. Tanuma, C. J. Powell, and D. R. Penn, "Calculations of electron inelastic mean free paths. V. Data for 14 organic compounds over the 50–2000 eV range," Surface and Interface Analysis, vol. 21, no. 3, pp. 165-176, 1994.
[15] D. F. Cox and K. H. Schulz, "Methanol decomposition on single crystal Cu2O," Journal of Vacuum Science & Technology A, vol. 8, no. 3, pp. 2599-2604, 1990.
[16] T. Koitaya, Y. Shiozawa, Y. Yoshikura, K. Mukai, S. Yoshimoto, and J. Yoshinobu, "Systematic Study of Adsorption and the Reaction of Methanol on Three Model Catalysts: Cu(111), Zn–Cu(111), and Oxidized Zn–Cu(111)," The Journal of Physical Chemistry C, vol. 121, no. 45, pp. 25402-25410, 2017/11/16 2017.
[17] S. Pöllmann, A. Bayer, C. Ammon, and H.-P. Steinrück, "Adsorption and Reaction of Methanol on Clean and Oxygen Precovered Cu(111)," Zeitschrift für Physikalische Chemie, vol. 218, no. 8, pp. 957-971, 2004.
[18] V. I. Bukhtiyarov, I. P. Prosvirin, E. P. Tikhomirov, V. V. Kaichev, A. M. Sorokin, and V. V. Evstigneev, "In situ study of selective oxidation of methanol to formaldehyde over copper," Reaction Kinetics and Catalysis Letters, vol. 79, no. 1, pp. 181-188, 2003/05/01 2003.
[19] Z. Besharat et al., "Dehydrogenation of methanol on Cu2O(100) and (111)," The Journal of Chemical Physics, vol. 146, no. 24, p. 244702, 2017.
[20] M. Setvin et al., "Methanol on Anatase TiO2 (101): Mechanistic Insights into Photocatalysis," ACS Catal, vol. 7, no. 10, pp. 7081-7091, Oct 6 2017.
[21] T. Fuhrmann et al., "Activated adsorption of methane on Pt(1 1 1) —an<i>in situ</i>XPS study," New Journal of Physics, vol. 7, pp. 107-107, 2005/04/29 2005.
[22] R. Larciprete, A. Goldoni, A. Groŝo, S. Lizzit, and G. Paolucci, "The photochemistry of CH4 adsorbed on Pt(111) studied by high resolution fast XPS," Surface Science, vol. 482-485, pp. 134-140, 2001/06/20/ 2001.
[23] Y.-Y. Hsia et al., "Effects of O2 and H2O in the Oxidative Steam-Reforming Reaction of Ethanol on Rh Catalysts," The Journal of Physical Chemistry C, vol. 123, no. 18, pp. 11649-11661, 2019/05/09 2019.
[24] Y.-C. Wu et al., "Catalyzed Decomposition of Methanol-d4 on Vanadium Nanoclusters Supported on an Ultrathin Film of Al2O3/NiAl(100)," The Journal of Physical Chemistry C, vol. 126, no. 8, pp. 3903-3914, 2022/03/03 2022.
[25] J. Greeley and M. Mavrikakis, "Competitive Paths for Methanol Decomposition on Pt(111)," Journal of the American Chemical Society, vol. 126, no. 12, pp. 3910-3919, 2004/03/01 2004.
[26] C.-S. Chao et al., "Two-Channel Decomposition of Methanol on Pt Nanoclusters Supported on a Thin Film of Al2O3/NiAl(100)," The Journal of Physical Chemistry C, vol. 117, no. 11, pp. 5667-5677, 2013/03/21 2013.
[27] H. J. Freund, H. Kuhlenbeck, J. Libuda, G. Rupprechter, M. Bäumer, and H. Hamann, "Bridging the pressure and materials gaps between catalysis and surface science: clean and modified oxide surfaces," Topics in Catalysis, vol. 15, no. 2, pp. 201-209, 2001/06/01 2001.
[28] A. V. Miller, V. V. Kaichev, I. P. Prosvirin, and V. I. Bukhtiyarov, "Mechanistic Study of Methanol Decomposition and Oxidation on Pt(111)," The Journal of Physical Chemistry C, vol. 117, no. 16, pp. 8189-8197, 2013/04/25 2013.